Questions and Answers on Prevention and Control of Highly Pathogenic Avian Influenza (Ⅱ)
Directory of Questions and Answers on Prevention and Control of Highly Pathogenic Avian Influenza (Ⅱ)
First, the concept, incidence and epidemic characteristics
What kind of virus is influenza virus and why is it easy to mutate?
2 What is the virus-carrying status of wild bird avian influenza virus?
Is the migration of wild birds one of the main causes of bird flu epidemic?
How to prevent wild birds from spreading influenza virus to poultry?
Is the avian influenza virus a new virus? How well do we know it?
What is the resistance of avian influenza virus, and how can we use these characteristics to carry out disease prevention?
From the distribution of the current epidemic situation, what are the characteristics of this bird flu epidemic in China? What does it mean?
With the warming of the climate and the migration of migratory birds to the north, is the situation of bird flu in the north more tense? What measures should we take?
Is there a rule to follow in the occurrence and development of avian influenza?
At present, what are the similarities and differences in the epidemic characteristics of avian influenza in Asian countries?
Is bird flu a new disease? What is its history and harm?
Two, prevention and control measures of highly pathogenic avian influenza
Why must the local people’s government organize and implement the treatment of bird flu epidemic areas? Can farmers handle it by themselves?
From the current situation, what measures should China take to prevent and control avian influenza?
Why is the epidemic area designated as a radius of 3 kilometers? Why is emergency immunization given to susceptible poultry 5 km away from the epidemic area?
According to the recent disposal of epidemic areas, do our emergency measures work?
When can I start raising chickens in epidemic areas where highly pathogenic avian influenza has occurred?
Why did the outbreak of avian influenza in Hong Kong be controlled so quickly in 1997, and the epidemic situation in China was not controlled in time, but it was still expanding?
What is a disinfectant? How to choose an effective disinfectant for avian influenza virus?
What are the principles for preventing and controlling major epidemics?
Why is it said that relying on science is the key link to prevent and control avian influenza?
How to understand the role of grass-roots veterinary epidemic prevention system in animal disease control?
How to standardize the feeding methods and conditions of poultry in China?
How to deal with virus-contaminated water sources? How to prevent water pollution caused by waterfowl?
Isn’t there a way to treat bird flu without killing animals?
What is the warning from the outbreak of avian influenza in China?
How to cull poultry in epidemic areas?
What is harmless treatment?
What are the technical specifications for harmless treatment?
How to clean and disinfect the epidemic area?
How to disinfect the farms and poultry houses of rural free-range households?
How should breeders in epidemic areas do well in the process of participating in the treatment of sick birds and site disinfection?
How to block and lift the blockade in epidemic areas?
Iii. Vaccine immunization
Is vaccine immunization effective for all poultry? Can we consider immunizing wild birds?
What should I pay attention to when immunizing inactivated avian influenza vaccine?
What measures has the Ministry of Agriculture taken to ensure the quality of avian influenza vaccine?
Many countries in the world do not advocate the use of avian influenza vaccine immunization. How to evaluate the rationality and scientificity of China’s avian influenza immunization policy?
How long does it take to produce immune protection after avian influenza vaccine injection? How long is the immunization period? What factors affect the immune effect of avian influenza vaccine?
Why can’t fake and inferior avian influenza vaccine products be used, and how to identify the true and false products from the logo?
Is it safe to use H5 subtype vaccine against highly pathogenic avian influenza?
Is vaccination an effective method to control the spread of highly pathogenic avian influenza under the current situation in China? What are its advantages and disadvantages compared with culling?
What are the good suggestions for the control of waterfowl diseases?
Four, the identification method of highly pathogenic avian influenza
What is the basis for the final diagnosis of this highly pathogenic avian influenza by the National Avian Influenza Reference Laboratory?
Can an abnormally dead chicken be considered as avian influenza?
What kinds of serological techniques are used to diagnose avian influenza in China at present? Which of them are the detection methods specified by OIE?
How to operate and determine the results of hemagglutination and hemagglutination inhibition test?
How to operate and determine the results of AGID test?
What are the diagnostic criteria for determining highly pathogenic avian influenza?
Is highly pathogenic avian influenza a chicken plague or Newcastle disease that has appeared before in China? How should they be distinguished?
Five, the correct treatment of highly pathogenic avian influenza
Is it possible for highly pathogenic avian influenza virus to spread vertically through eggs after it infects chickens?
Is the avian influenza virus directly transmitted to people through poultry?
Will consumers affect people’s health after eating poultry vaccinated with avian influenza?
Can the dead chickens be eaten after high-temperature processing?
How should the staff directly involved in killing birds do personal protection?
How should the reporters who go to the epidemic area do well in protection?
Six, highly pathogenic avian influenza prevention and control related knowledge
What is zoonosis? What are the common zoonotic diseases?
What are the main contents of the emergency plan for handling highly pathogenic avian influenza in China?
How does OIE classify animal diseases? How is China divided?
What diseases are the first, second and third types of animal diseases defined by China?
Why should China inform FAO, WHO and neighboring countries and regions of the avian influenza epidemic in time?
What kind of international organizations are WHO, FAO and OIE? What are the specific functions?
First, the concept, incidence and epidemic characteristics
What kind of virus is influenza virus and why is it easy to mutate?
Influenza virus, IV) belongs to Orthomyxoviridae. The virus genome consists of eight negative-strand single-stranded RNA fragments, and the membrane contains glycoprotein fibrils with hemagglutinin and neuraminidase activity. According to different antigenicity, it can be divided into three types: A, B and C, and its type specificity is determined by the antigenic properties of nucleoprotein (NP) and matrix (M) antigens. Influenza A virus can be found in humans, many kinds of birds, pigs and horses, and other mammals, while types B and C are generally only found in humans. According to the antigenic characteristics of hemagglutinin (HA) and neuraminidase (NA), influenza A virus is divided into different subtypes. At present, there are 15 specific HA subtypes and 9 specific NA subtypes.
Influenza virus belongs to segmented RNA virus, and the gene recombination rate among different strains is high, and the antigenic variation frequency of influenza virus is fast. The variation is mainly carried out in two ways: antigen drift and antigen transformation. Antigen drift can cause minor antigen changes of HA and/or NA, while antigen transformation can cause major antigen changes of HA and/or NA. Single site mutation can change the structure of surface protein, so it also changes its antigenic or immunological characteristics, leading to antigenic variants. However, when cells are infected with two different influenza virus particles, the eight genome segments of the virus can be randomly exchanged and gene rearrangement occurs. It is possible to produce highly pathogenic strains by gene rearrangement. Gene rearrangement only occurs between viruses of the same kind, which is different from gene recombination. This is why influenza viruses are prone to mutation.
2 What is the virus-carrying status of wild bird avian influenza virus?
One of the epidemiological characteristics of avian influenza is that the disease is distributed worldwide with the migration of migratory birds or waterfowl. Wild bird influenza viruses are all influenza A viruses. Among the found avian influenza viruses, there are 9 different neuraminidase antigens and 14 of 15 different hemagglutinins. At present, H13 subtype virus is only found in coastal birds and gulls, and other serotype viruses can be isolated from wild waterfowl and permanently exist in waterfowl or migratory birds all over the world. H7, H5 subtype avian influenza in the world, For example, Queensland and Victoria (H7N9, H7N9 and H7N9) in Australia, Hong Kong (H5N1) in China, Pakistan (H7N9), South Africa (H5N1), Italy (H5N1), Germany (H7N9), Britain (H7N9), Ireland (H5N8), England (H7N9) and Scotland (H5N1). Pennsylvania (H5N2) and Mexico (H5N2) in the United States are almost all island countries or coastal areas, and the epidemic spots are close to oceans or lakes, which are closely related to the migration and habitat of migratory birds.
Is the migration of wild birds one of the main causes of bird flu epidemic?
The answer is yes. A large number of influenza viruses were found in many kinds of birds, indicating that there are huge influenza virus gene banks and antigen banks in birds all over the world. Scientists have isolated many different influenza viruses with the combination of hemagglutinin and neuraminidase, which makes people think that there must be all kinds of single or mixed influenza virus infections in birds all over the world, and they can permanently exist in waterfowl or migratory birds all over the world, because avian influenza virus can fully proliferate in intestinal cells of waterfowl (especially wild ducks) without showing any clinical symptoms, and is highly concentrated in feces and excreted in water systems and other areas with feces. It causes extensive pollution, which means that the avian influenza virus that is not pathogenic to wild birds such as wild ducks has many opportunities to spread directly or indirectly to a large number of poultry, especially poultry raised outdoors, such as chickens, ducks, geese and turkeys.
How to prevent wild birds from spreading influenza virus to poultry?
Wild birds, especially migratory waterfowl, are recognized as one of the sources of avian influenza infection in poultry. Cutting off the spread of influenza virus from wild birds to poultry is an important measure to control avian influenza. Therefore, poultry, especially waterfowl, should not be kept in the area where wild birds are active. Ducks and geese should be kept in captivity on land, and feces should be regularly taken from places frequented by wild birds to monitor the pathogens. If there are pathogens, they should be thoroughly disinfected. Vaccinate poultry susceptible to wild birds. Special attention should be paid to the migration and transit of migratory birds and the epidemic prevention of waterfowl in stranded waters.
Is the avian influenza virus a new virus? How well do we know it?
Avian influenza virus is not a new virus, it has existed for a long time and has been recognized by people. The first discovery of avian influenza was in 1878, and it was confirmed in 1955 that it was caused by type A avian influenza virus. For a long time, people have made in-depth and systematic research on the morphology, pathogenicity, resistance, molecular biological characteristics, epidemiology, pathogenic mechanism, clinical manifestations, pathological changes, diagnostic methods and epidemic prevention control technology of avian influenza virus, and have a very comprehensive and systematic understanding of it and achieved a large number of research results. In recent years, China has also done a lot of research in this field, and made gratifying breakthroughs and achievements in epidemiological investigation, diagnostic techniques, preventive vaccines and virus molecular biology research.
What is the resistance of avian influenza virus, and how can we use these characteristics to carry out disease prevention?
Avian influenza A virus is an envelope virus, which is sensitive to lipid solvents such as detergents and has weak resistance. Common disinfectants can kill it easily, such as formalin, oxidant, chlorine-containing disinfectants, alkaline preparations, dilute acid, sodium deoxycholate, hydroxylamine, sodium dodecyl sulfate and ammonium ions. The virus is not heat-resistant, and it will lose its activity after being heated at 60℃ for 10 minutes and 70℃ for several minutes. However, the virus has a strong resistance to low temperature, and can remain active for more than one year under the protection of glycerol. The virus can be killed in 40~48 hours under direct sunlight. Direct ultraviolet rays can destroy its infectivity, hemagglutinin activity and neuraminidase activity.
In the field, avian influenza virus is often discharged from nasal secretions and feces of infected birds. The virus is protected by these organic substances, which greatly increases its resistance to inactivation. To inactivate the virus in the environment, all sick chickens should be killed first, then effective disinfectants should be sprayed on the whole enclosure to remove the organic substances, including feces, and then the surface should be cleaned with detergent, and then disinfected with sodium hypochlorite solution and formalin fumigation to kill the contaminated influenza virus in the house.
The main problem of controlling highly pathogenic avian influenza is how to control seriously polluted feces. Mat and feces can be treated by burying, covering with plastic for composting and fermentation.
From the distribution of the current epidemic situation, what are the characteristics of this bird flu epidemic in China? What does it mean?
Judging from the distribution of the current epidemic situation, the epidemic of avian influenza in China belongs to a sporadic situation. From south to north, the disease is acute, the incubation period is short, and the morbidity and mortality are high; The transmission between flocks mainly depends on horizontal transmission; Up to now, only chickens, ducks and other poultry have been found infected or sick, and no one has been found infected. According to the analysis of the epidemic situation of avian influenza, the migration of wild birds may be one of the important reasons for the epidemic.
With the warming of the climate and the migration of migratory birds to the north, is the situation of bird flu in the north more tense?
What measures should we take? Winter leaves and spring comes, and spring blooms. A large number of migratory birds wintering in epidemic areas return to the north. The epidemic of avian influenza in the north will face a new grim situation. We must earnestly do a good job in the prevention of avian influenza. To stop migratory birds from spreading avian influenza virus, we can take the following measures under the premise of observing the wildlife protection law:
(1) Pay close attention to the habitat and incidence of migratory birds in garden ponds, zoos (including wild zoos) and major reservoirs in various urban areas and counties. Once abnormal symptoms and deaths of migratory birds are found, they should immediately report to the local animal husbandry and veterinary department to diagnose the cause of death of dead migratory birds, and take measures such as disinfection for areas that may be polluted by death.
(2) After the experts confirm it as a suspected case, carry out the separation and identification of the pathogen. According to the pathogenicity of the isolated avian influenza virus, delimit the epidemic area, immediately close the habitat of migratory birds, thoroughly disinfect parks and ponds, and isolate and inspect ducks, swans and geese in parks.
(3) Feces discharged by poisonous migratory birds can infect other birds in parks and ponds. It is suggested that bird nets should be installed around parks and ponds where migratory birds are easy to inhabit, so as to prevent migratory birds from landing, inhabiting and feeding, and reduce the chance of migratory birds discharging avian influenza virus.
(4) Poultry (including ducks, chickens and other susceptible birds) within 3 km around large water surfaces such as reservoirs and lakes is strictly prohibited.
(5) In conjunction with forestry and other departments, carry out the investigation on the situation of migratory birds carrying avian influenza virus, and initially find out which birds carry the virus and the infection rate in the areas where migratory birds migrate.
(6) Strengthen the management of farmers’ free-range poultry, strengthen vaccination and environmental disinfection; For intensive poultry farms, it is necessary to standardize management, compulsory immunization and strengthen sanitation and disinfection; Restrict live poultry trading and transportation, and standardize market management and quarantine work.
(7) Emergency immunization with avian influenza vaccine is carried out on the susceptible birds (ducks, geese, geese, herons, peacocks, black-bone chickens, etc.).
Is there a rule to follow in the occurrence and development of avian influenza?
Because of the spread of avian influenza virus, wild birds (mainly migratory birds) are common and the main source of infection, and the frequent trade in poultry products in the world will cause the outbreak and epidemic of avian influenza. Judging from the occurrence of avian influenza in the world, there are uncertainties in the spread, occurrence and development of avian influenza. Therefore, from the current situation, there is no obvious regularity in the occurrence and development of avian influenza.
At present, what are the similarities and differences in the epidemic characteristics of avian influenza in Asian countries?
Except that Taiwan, China reported that it was caused by avian influenza virus H5N1 with low pathogenicity and Pakistan was caused by H7 subtype, South Korea, Japan, Viet Nam, Thailand, Indonesia and China were all caused by avian influenza virus H5N1 with high pathogenicity. The outbreak of avian influenza in Asia has the characteristics of rapid spread, strong infectivity, high mortality rate and many countries and regions involved, and all of them occurred in winter or early spring. There are reports that people are infected with H5N1 in Vietnam, Thailand and Indonesia, but no human infection has been found in Korea, Japan and China. The source of infection and transmission route that caused the outbreak and epidemic of highly pathogenic avian influenza in Asia need further study.
Is bird flu a new disease? What is its history and harm?
Avian influenza is short for avian influenza. Among them, highly pathogenic avian influenza is a severe infectious disease of poultry caused by influenza A virus. It is classified as a Class A infectious disease by the OIE because of its rapid spread, high morbidity and mortality. Once it breaks out, it will cause a devastating blow to the poultry industry. Avian influenza is not a new disease. In 1878, it was first reported that a serious disease broke out in Italian chickens, which was called chicken plague at that time. It was only in 1955 that it was confirmed that this fowl plague virus was actually a type A avian influenza virus, and it was officially named avian influenza at the first international avian influenza conference in 1981. It has been proved that avian influenza virus is widely distributed in many poultry worldwide, including chickens, turkeys, guinea fowl, partridges, ostriches, ducks, pheasants, quails, pigeons, geese and wild birds (ducks, geese, terns, swans, herons, sea doves, puffins and gulls, etc.). Among them, avian influenza is the most harmful to domestic chickens and turkeys, and in recent years, a large number of infected ducks have also died.
In the recorded history of poultry diseases, avian influenza is a devastating disease, and every serious outbreak has caused huge economic losses to the poultry industry. It has occurred in many countries and regions in the world, such as America, Europe, Asia, Africa and Oceania. Before 1990s, there were eight outbreaks of avian influenza in Scotland (1959), Britain (1967), Australia (1975), Britain (1979), Iceland (1983), America (1983) and Iceland (1999). Since the 1990s, there have been four outbreaks of avian influenza, namely, H7N9 and H7N9 in Australia, H7N9 in Pakistan, H5N2 in Mexico and H7N1 in Italy. Avian influenza can cause huge economic losses. In 1983-1984, the outbreak of avian influenza in Pennsylvania and Virginia in the United States caused a loss of $40 million. The outbreak of avian influenza in Mexico in 1994 was more complicated and unforgettable than that in Pennsylvania in 1983. In 1981-1982, the national serological survey of poultry in Mexico did not find the infection of avian influenza virus. In May 1994, the epidemic of low virulence H5N2 was discovered. In January 1995, it suddenly became a highly virulent strain, and it was prevalent in Puebla and Queretaro, and quickly spread to 12 states. In order to control the epidemic, 18 million chickens were eliminated.32 million chickens were blocked and 130 million chickens were vaccinated urgently, resulting in direct economic losses of $1 billion. In 1997 and 2001, avian influenza broke out in Hong Kong, and the SAR Government spent HK$ 1.8 billion successively, killing 2.7 million chickens twice.
Two, prevention and control measures of highly pathogenic avian influenza
Why must the local people’s government organize and implement the treatment of bird flu epidemic areas?
Can farmers handle it by themselves? After the outbreak of highly pathogenic avian influenza, farmers cannot handle it by themselves. The National Animal Epidemic Prevention Law clearly stipulates that all poultry and poultry products in epidemic areas must be culled and treated harmlessly under the supervision of the supervising agencies for animal epidemic prevention. All items that may be contaminated must also be disinfected and treated harmlessly. In addition, the blockade of epidemic areas, the forced culling of poultry in epidemic areas, the control of environmental disinfection, the confirmation of epidemic situation and the economic compensation for culling animals can only be organized and implemented by the local government and the animal husbandry and veterinary administrative department, and no farmer can complete this task alone. Farmers slaughter at will, and if blood, waste and polluted water are not treated or treated improperly, it will cause serious environmental pollution and spread of pathogens.
Highly pathogenic avian influenza is classified as a class A infectious disease by the World Organization for Animal Health (OIE), and it is classified as a class of animal infectious disease in China. When it is confirmed as highly pathogenic avian influenza, it is necessary to immediately block the epidemic area, cull the sick birds and thoroughly disinfect the environment, in order to prevent the epidemic from spreading further, which is also stipulated in China’s animal epidemic prevention law.
From the current situation, what measures should China take to prevent and control avian influenza?
At present, the epidemic situation has not been effectively controlled, and new epidemics are still emerging, and there are still many unknowns. Therefore, in order to prevent the epidemic from spreading, it must be resolutely implemented in accordance with the requirements stipulated in the Law of People’s Republic of China (PRC) on Animal Epidemic Prevention and the National Emergency Plan for Highly Pathogenic Avian Influenza. Quarantine and block suspected sick birds. When the highly pathogenic avian influenza is diagnosed, the poultry in the epidemic area should be culled immediately, and the culled poultry must be burned and buried deeply. Thoroughly disinfect the polluted environment in order to prevent the epidemic from spreading further. Implement emergency vaccination of all susceptible poultry within 5 kilometers around the epidemic area, establish an immune isolation belt, and gradually vaccinate all susceptible poultry. Ensure that the epidemic situation is quickly and effectively controlled.
Why is the epidemic area designated as a radius of 3 kilometers?
Why is emergency immunization given to susceptible poultry 5 km away from the epidemic area? It is an international practice for China to designate the radius of 3 kilometers around the epidemic area of avian influenza as the epidemic area. Because all the poultry within a radius of 3 kilometers around the epidemic spot are the most susceptible to infection, it is absolutely necessary to cull all the poultry within a radius of 3 kilometers around the epidemic spot in order to ensure that the epidemic situation of highly pathogenic avian influenza can be completely and thoroughly extinguished, which will be beneficial to control the spread of pathogens caused by sick poultry, their feces, sewage and other pollution sources, which is the most effective way to control severe infectious diseases. Emergency immunization of sensitive poultry in an area 5 kilometers away from the epidemic area aims at establishing an immune isolation zone, which can not only protect poultry in the threatened area from infection, but also provide a biological barrier for poultry in non-epidemic areas from infection. Therefore, it is necessary to establish an immune isolation belt.
According to the recent disposal of epidemic areas, do our emergency measures work?
In the recent stage, China’s disposal measures for epidemic areas are: reporting the epidemic situation in time when highly pathogenic avian influenza occurs, finding the epidemic source point, blocking the epidemic point in a short time, and culling poultry in the epidemic area. Implement emergency vaccination for sensitive birds in threatened areas and establish immune isolation zones. In order to prevent the spread of the disease, the pathogen isolation of highly pathogenic avian influenza must be carried out in a laboratory with BSL3 conditions designated by the Ministry of Agriculture. Judging from the recent situation, this disposal measure is feasible and has effectively controlled the spread of the epidemic, and no large-scale epidemic has occurred around the epidemic area. If we don’t take such compulsory measures and let the disease spread at will, the consequences will be unimaginable.
When can I start raising chickens in epidemic areas where highly pathogenic avian influenza has occurred?
All poultry and their products in the epidemic area shall be thoroughly disinfected under the supervision of the local supervising agency for animal epidemic prevention after being treated according to regulations. Twenty-one days later, the local animal husbandry and veterinary administrative department shall apply to the government that originally issued the blockade order for the release of the blockade when the animal epidemic prevention supervisor considers that the blockade can be lifted. After the blockade of the epidemic area is lifted, it is necessary to continue to monitor the epidemic situation in this area. Under normal circumstances, if no new pathogen is found in the epidemic area within 6 months, chickens can be raised again. Before entering the chicken farm, the chicken farm should be thoroughly fumigated with formalin, and the chicken can be started after a few days of open space.
Why did the outbreak of avian influenza in Hong Kong be controlled so quickly in 1997, and the epidemic situation in China was not controlled in time, but it was still expanding?
Compared with the mainland, Hong Kong has a small geographical area, surrounded by the sea and a small number of poultry. Therefore, by blocking, isolating and culling all poultry, the source of infection is completely eliminated, and comprehensive prevention measures such as disinfection can be taken to comprehensively and effectively control the epidemic situation. However, the large number of chickens in mainland China, the large number and wide range of free-range farming in rural areas, and the frequent circulation of breeding birds and poultry products are conducive to the spread of the epidemic, which also makes it more difficult to control the bird flu epidemic in China.
What is a disinfectant? How to choose an effective disinfectant for avian influenza virus?
Disinfectant refers to a chemical reagent that can quickly kill pathogenic microorganisms in a short time. Common disinfectants can kill avian influenza virus, and 01% bromogeramine, 01% double quaternary ammonium salt or 01% disinfectant can be used for washing and surface disinfection. Chlorine preparation can be used to disinfect the air in the house, and 01% 84 disinfectant, 01% peracetic acid, 1% ~ 2% formalin solution, 1% ~ 2% caustic soda solution, 05% ~ 1% compound phenol and 5% bleaching powder solution can be used to disinfect the environment, poultry houses and utensils. Textiles can be disinfected by soaking in chlorine-containing disinfectant with effective chlorine of 250 mg/ml for 30 minutes, or by fumigation with peracetic acid. Poultry houses and cages are cleaned with sodium hypochlorite and then fumigated with formalin. The specific use method is carried out according to the product manual.
What are the principles for preventing and controlling major epidemics?
The prevention and control of major epidemics should be based on the basic principle of "prevention is more important than cure", and comprehensive preventive measures should be taken. The principle of "early, fast, strict and small" should be adopted to control and extinguish the epidemic, so as to achieve early detection and diagnosis; Quickly deal with the epidemic situation and isolate sick animals (poultry) in time; Blockade epidemic areas, cull sick animals (birds), and control the epidemic situation to a minimum.
Why is it said that relying on science is the key link to prevent and control avian influenza?
Avian influenza has a history of more than 100 years, and there are extensive and in-depth studies on the disease at home and abroad. I am familiar with the biological characteristics, epidemic characteristics and transmission modes of avian influenza virus, and have accumulated rich experience in diagnosis technology, immune control technology and prevention and control. Only by scientific diagnosis, qualified vaccines and comprehensive prevention and control measures can the epidemic be extinguished. According to the characteristics of the occurrence and epidemic of avian influenza in the world, in order to ensure the safe production of poultry industry, China has made a number of scientific research achievements in the prevention and immunization of avian influenza in the major scientific and technological research projects of the country, the natural science foundation and the national "973" major basic research project. Therefore, relying on the existing scientific knowledge and related new technologies is the key link to control avian influenza.
How to understand the role of grass-roots veterinary epidemic prevention system in animal disease control?
Grass-roots veterinary epidemic prevention system plays an irreplaceable role in animal disease prevention, disease diagnosis, treatment, epidemiological detection, discovery and disposal of epidemic situation, collection of relevant disease data and epidemic situation reporting, and it is the front sentry of animal disease prevention and control. Therefore, it is necessary to strengthen and improve the grass-roots veterinary epidemic prevention system in China.
How to standardize the feeding methods and conditions of poultry in China?
China’s rural areas are vast, and raising poultry by farmers themselves is one of the main methods of raising poultry at present. Therefore, a good and scientific feeding method is the key to prevent avian influenza. Proceeding from the reality, we should do the following work:
(1) Poultry should be raised indoors, and poultry farms should be far away from public places, traffic arteries and other animal production sites, and away from rivers and lakes where wild birds inhabit.
(2) It is forbidden to mix different poultry, such as chickens, ducks and geese, and to mix poultry and pigs.
(3) Birds and mice, such as sparrows, are forbidden to enter the poultry house. These animals are usually carriers of pathogenic microorganisms.
(4) The introduction must be healthy and free from infectious diseases, and the system of all-in and all-out poultry breeding shall be implemented.
(5) Do a good job in the daily disinfection and hygiene of poultry houses and breeders. The poultry houses should be cleaned and disinfected frequently, and the poultry houses should be thoroughly disinfected before and after each poultry entry.
(6) The breeder shall be disinfected when entering or leaving the poultry house, so as to avoid going from house to house, and irrelevant personnel shall not enter the poultry house. Strict disinfection should be carried out on farms, passing vehicles and the environment around the site.
(7) Immunization should be carried out under the guidance of the local animal husbandry and veterinary department, and serological monitoring should be carried out regularly to ensure that the immune prevention effect of the vaccine is reliable.
(8) Ensure reasonable feeding density, good ventilation and high-quality clean feed.
How to deal with virus-contaminated water sources? How to prevent water pollution caused by waterfowl?
When the water source is polluted by virus, waterfowl are forbidden to enter again at first. For sewage in small water bodies, 10 ml of 1% available chlorine-containing disinfection solution or 4 g of bleaching powder is added for 15-2 hours after mixing. The management of large water bodies should be strengthened, and it is strictly prohibited to use them before the blockade is lifted in epidemic areas. Drinking water in epidemic areas should be tested, and if it is polluted, it should be disinfected to ensure that the microbial indicators meet the Hygienic Standard for Drinking Water. Viral waterfowl and its pollutants entering the water source is one of the important causes of water pollution, so waterfowl should be kept in captivity, poultry farms and slaughterhouses should be far away from the water source, and poultry house garbage, waterfowl secretions, excreta and slaughterhouse waste should not be poured into the water source.
Isn’t there a way to treat bird flu without killing animals?
At present, there is no effective treatment for highly pathogenic avian influenza. Once the disease occurs, it can only be treated by culling, burning and deep burial. The treatment can only delay the time and cause the spread of the disease. In the breeding industry, the viral infectious diseases of animals are mainly prevented by vaccinating healthy livestock and poultry.
What is the warning from the outbreak of avian influenza in China?
The occurrence of bird flu in China is basically in some small individual farms, which are relatively poorly managed and have chaotic feeding methods. Therefore, it warns us that the occurrence and control of bird flu are closely related to the feeding methods of poultry, and good feeding management conditions are the key to prevent bird flu. Especially in South China and Southeast Asia, the water system is relatively developed. In winter, a large number of migratory birds migrate here for the winter. Because these wild birds, especially waterfowl, may carry avian influenza virus, poultry may be infected with avian influenza through direct and indirect contact with wild birds.
Therefore, it is suggested that special attention should be paid to the prevention and control of avian influenza:
(1) Strengthen prevention and control measures, strictly clean and disinfect farms, utensils and means of transport, and adopt the all-in and all-out feeding method to control the flow of farm personnel.
(2) Strictly prevent the introduction of highly pathogenic avian influenza into China, strengthen border trade and border management, ban the border live poultry trade, severely crack down on illegal entry of birds and their products, and at the same time, avoid contact between poultry and wild birds, especially waterfowl.
(3) Establish an avian influenza disease monitoring network as soon as possible.
How to cull poultry in epidemic areas?
The following methods can be adopted to cull live birds:
(1) Asphyxia: firstly, put the birds to be culled into bags, put them into sealed cars or other sealed containers, and introduce carbon dioxide to suffocate them to death; Or put the birds in a sealed bag and introduce carbon dioxide to suffocate them to death.
(2) When the amount of neck-twisting culling is small. According to the size of the bird, hold the head with one hand and the body with the other hand, and twist the pull in the opposite direction.
(3) Others can also adopt other lethal methods that can avoid the spread of pathogens according to local conditions.
What is harmless treatment?
By physical, chemical or biological methods, the infected animals, animal products and excreta are disinfected to inactivate the pathogen and ensure that it does not pose harm to human beings, animals and the environment, which is harmless treatment.
What are the technical specifications for harmless treatment?
All sick and dead birds, culled birds and their products, excreta, and padding, feed and other articles that are polluted or may be polluted shall be treated harmlessly.
Harmless treatment can choose deep burial, incineration, incineration and other methods, and feed and feces can also be fermented.
(1) Deep burial
(1) deep buried points should be far away from residential areas, water sources and traffic arteries, away from public view, and clearly marked.
(2) the thickness of the covering soil layer of the pit should be greater than 15m, the bottom of the pit should be paved with quicklime, and a layer of quicklime should be sprinkled before covering the soil. The location and type of pits should be conducive to flood control.
(3) after the dead birds are placed in the pit, they are burned with oil, and then covered with soil, even with the surrounding area. Don’t fill the soil too tightly, so as to avoid gas bubbles and liquid leakage caused by corpse decay.
(4) feed, pollutants, etc. are placed in the pit, sprayed with disinfectant and buried.
(2) Incineration and incineration
① If there is a large cremator near the epidemic area, incineration can be used.
(2) if the amount of treated corpses and pollutants is small, a pit 15 meters deep can be dug and burned with oil.
(3) Fermented feed and feces can be piled up in designated places and sealed for fermentation.
The above treatment should meet the requirements of environmental protection, and the involved links such as transportation, loading and unloading should be avoided, and the transportation and loading tools should be thoroughly disinfected.
How to clean and disinfect the epidemic area?
(1) set up a cleaning and disinfection team. The cleaning and disinfection team should be guided by a professional and technical personnel.
(2) Equipment and necessities
① Cleaning tools: brooms, forks, shovels, shovels and flushing water pipes.
② Disinfection tools: sprayers, flame spray guns, disinfection vehicles, disinfection containers, etc.
③ Disinfectants: aldehydes, oxidants, chlorine preparations, bis-quaternary ammonium salts and other suitable disinfectants.
④ Protective equipment: protective clothing, masks, rubber boots, gloves, goggles, etc.
(3) Cleaning, cleaning and disinfection of poultry farms
(1) first clean up dirt, feces, feed, padding, etc.
(2) Thoroughly wash the ground and all kinds of appliances, and wash poultry houses and vehicles with water to treat the generated sewage harmlessly.
③ The metal facilities and equipment in poultry farms can be disinfected by flame and fumigation.
(4) poultry pens, venues, vehicles, etc., can be disinfected by spraying disinfectant.
⑤ The feed and padding of poultry farms are buried deeply, fermented or burned.
⑥ Buried, stacked, sealed, fermented or incinerated excrement.
⑦ The office areas, dormitories for breeders, public canteens, roads and other places in the epidemic area should be sprayed for disinfection.
Today sewage ditch can be put into quicklime or bleaching powder.
(4) vehicle cleaning and disinfection
(1) temporary disinfection points shall be set up on the main roads entering and leaving epidemic spots and epidemic areas to disinfect the personnel, means of transport and related articles.
(2) all vehicles that may be contaminated in the epidemic area should be strictly disinfected, and the outside, inside and all corners and gaps of vehicles should be washed with clean water and disinfected with disinfectant, leaving no dead ends.
(3) the items on the vehicle should also be disinfected.
(4) the garbage and feces cleaned from the vehicle should be treated harmlessly.
(5) Cleaning and disinfection of poultry markets and cages
① Spray all areas with disinfectant.
② Feed and feces should be buried deeply, fermented or burned.
(3) scraping and cleaning all items such as cages, and thorough disinfection. The generated sewage should be treated harmlessly.
(6) Cleaning and disinfection of slaughter, processing, storage and other places
① All poultry and poultry products in epidemic areas should be buried or burned.
② Poultry houses, cages, aisles and areas outside houses should be cleaned and sprayed with disinfectant.
(3) all equipment, tables, refrigerators, floors, walls, etc. should be washed clean and sprayed with disinfectant for disinfection.
(4) the clothes used are soaked in disinfectant and cleaned, and other items should be disinfected in an appropriate way.
⑤ The sewage generated above should be treated harmlessly.
How to disinfect the farms and poultry houses of rural free-range households?
(1) After culling chickens, ducks and other birds, the site must be cleaned and disinfected.
(2) Wear protective clothing before cleaning and disinfection.
(3) The droppings in poultry houses should be thoroughly removed, and the bird droppings scattered in the yard should be collected, and stacked, sealed, fermented or incinerated.
(4) When cleaning up the accumulated poultry manure, spray water, and do not raise manure dust.
(5) Thoroughly disinfect the site and poultry house with disinfectant, and the used personal protective articles such as gloves, plastic bags and masks should be destroyed.
(6) Reusable articles shall be washed twice with detergent to ensure cleanliness.
(7) Soak the clothes worn during culling in hot water above 70℃ for more than 10 minutes, then wash them with soapy water and dry them in the sun.
(8) Wash your hands and take a bath after handling the dirt.
How should breeders in epidemic areas do well in the process of participating in the treatment of sick birds and site disinfection?
(1) Before the breeders come into contact with contaminated birds or feces, they must wear masks, gloves and goggles, protective clothing and rubber boots.
(2) If the breeders of free-range households do not have these protective equipment, they should use other items as flexibly as possible instead. For example, cover your nose and mouth with cloth instead of a mask, wrap your head and feet with plastic bags, or wrap your body with other washable things.
(3) Personnel dealing with birds and related cleaning and disinfection work should wear protective articles.
(4) After the site is cleaned and disinfected, wash your hands and take a bath after taking off protective articles.
(5) Clothes should be soaked in hot water above 70℃ for 10 minutes, then washed with soapy water and dried in the sun.
(6) Destroy disposable gloves, plastic bags and other related items.
(7) Rubber boots and goggles should be cleaned and disinfected.
(8) Wash your hands after handling the above items.
(9) Children are not allowed to participate in the above work.
How to block and lift the blockade in epidemic areas?
(1) The local animal husbandry and veterinary administrative department shall designate epidemic spots, epidemic areas and threatened areas.
(2) Release of Blockade Order The animal husbandry and veterinary administrative department shall report to the people’s government at the same level to block the epidemic area, and the people’s government shall make a decision immediately after receiving the report. If a blockade is decided, a blockade order shall be issued.
(3) Implementation of blockade The local people’s government organized a blockade of the epidemic area. Set warning signs around the epidemic area, set up temporary quarantine and disinfection stations at traffic intersections entering and leaving the epidemic area, assign special personnel and equip with disinfection equipment, prohibit the entry and exit of susceptible live birds and the delivery of susceptible poultry products, and strictly disinfect the personnel and vehicles entering and leaving.
(4) Release of the Blockade Order After all poultry and poultry products in the epidemic area have been dealt with according to the regulations, after more than 21 days of monitoring, no new source of infection has appeared, and the pathogen in the threatened area has been tested negative. After passing the inspection by the supervising personnel for animal epidemic prevention, the local animal husbandry and veterinary administrative department shall apply to the people’s government that issued the blockade order for the release of the blockade.
Iii. Vaccine immunization
Is vaccine immunization effective for all poultry? Can we consider immunizing wild birds?
Under the condition that the organism function of poultry is in good condition, the effective rate of the vaccine can reach 80% or higher after immunizing poultry, but there will be some differences due to the variety of poultry, genetic factors, nutritional status, environmental factors, vaccine quality, maternal antibodies, organism status and other reasons. The inactivated H5N2 vaccine used in China has a good immune effect on chickens, but the immune effect on waterfowl such as ducks needs to be evaluated. At present, Chinese scientists are speeding up the development of a new vaccine, and its immune effect will obviously exceed that of the vaccine currently used. As far as the current conditions are concerned, it is difficult and unrealistic to vaccinate wild birds.
What should I pay attention to when immunizing inactivated avian influenza vaccine?
Attentions should be paid to inactivated vaccine: firstly, it should be carried out under the condition of good poultry body; Secondly, inactivated vaccines generally need to be immunized for more than 2 times, and intramuscular inoculation is used; Thirdly, when young poultry are immunized for the first time, the peak period of maternal antibody should be avoided as far as possible. In addition, the immunization of waterfowl such as ducks may have some side effects.
What measures has the Ministry of Agriculture taken to ensure the quality of avian influenza vaccine?
Measures taken to ensure vaccine quality mainly include:
(1) Standardize production, carry out GMP certification for vaccine manufacturers, and those who fail to meet the requirements are not allowed to produce avian influenza vaccines;
(2) strictly control the quality of raw materials used in vaccine production, and those that do not meet the standards are not allowed to be used in vaccine production;
(3) unify the seed virus and quality standards for vaccine production, and strictly control the quality inspection of vaccines;
(4) China Veterinary Drug Supervision Institute sends factory supervisors to each avian influenza vaccine production enterprise to supervise the whole process of vaccine production and inspection;
(5) The system of batch issuance and sampling inspection shall be implemented for finished vaccine products;
(6) affixed with anti-counterfeiting labels uniformly printed by China Veterinary Drug Control Institute;
(7) investigate and deal with fake, counterfeit and inferior products.
Many countries in the world do not advocate the use of avian influenza vaccine immunization. How to evaluate the rationality and scientificity of China’s avian influenza immunization policy?
In order to eradicate the pathogen completely, some developed countries basically adopted culling measures in the previous prevention and control work of highly pathogenic avian influenza, which is convenient for fundamentally eliminating avian influenza. However, some countries allow the use of vaccines in emergencies. For example, in 1994, Mexico finally controlled the epidemic through vaccine immunization. Pakistan also adopts the strategy of vaccine immunization to control the epidemic situation. The United States allows turkeys to use inactivated avian influenza vaccine, while Italy uses vaccines against low virulence strains, but does not advocate the use of live vaccines. Recently, FAO, WHO and OIE reached a consensus on the prevention and treatment of avian influenza in Rome, Italy, and vaccine immunization was regarded as a major measure to control highly pathogenic avian influenza. China is a big farming country, with scattered farmers and relatively poor farming conditions (especially small farmers’ farms), so it is difficult to control avian influenza, especially in the case that avian influenza occurs in many provinces, cities and regions at the same time, it is very necessary and feasible to adopt culling as the main method, and at the same time, carry out vaccine immunization and establish immune isolation zones. In addition, the vaccine strain in China is a weak H5N1 strain, and after strict inactivation, it will not cause the problem of virus dispersion due to vaccination, which also provides feasibility for differential diagnosis of wild H5N1 infection.
How long does it take to produce immune protection after avian influenza vaccine injection? How long is the immunization period? What factors affect the immune effect of avian influenza vaccine?
Generally speaking, it takes 14 days for the body to produce immune protection after inactivated vaccine injection. The immune period of the vaccine is 4 months. Under the premise of ensuring the quality of the vaccine, the vaccine must be stored at 2 ~ 8℃. In addition, the time, variety, maternal antibody, inoculation route and corresponding comprehensive prevention and control measures have a decisive impact on the immune effect of avian influenza vaccine. It should be noted that if you have been infected with avian influenza virus before the immune protection of the vaccine is produced, avian influenza will also occur despite vaccination.
Why can’t fake and inferior avian influenza vaccine products be used, and how to identify the true and false products from the logo?
Fake and shoddy vaccine products are usually not tested for safety and efficacy, the quality of the vaccine is not guaranteed, and its corresponding immune effect is difficult to determine; If the vaccine virus is not completely inactivated, it will also cause the spread of diseases. And once the use of fake and inferior avian influenza vaccine, there is an abnormal situation or cause great losses, it is difficult to find the responsible person, lack of legal protection.
Regular vaccines have the production number issued by the veterinary administrative department, and the label design conforms to the national regulations, including the manufacturer, production date, approval number, batch number, address and contact telephone number, and special anti-counterfeiting labels printed by China Veterinary Drug Supervision Bureau are affixed.
Is it safe to use H5 subtype vaccine against highly pathogenic avian influenza?
Up to now, all highly pathogenic avian influenza viruses are caused by subtype H5 or H7 of influenza A virus. Although most of the outbreaks of avian influenza in Asia and China are subtype H5, it cannot be considered foolproof only by using subtype H5 vaccine. One subtype of vaccine is only effective for diseases caused by one subtype of virus. Recently, H7 subtype of avian influenza appeared in the United States, so we must take it seriously. In addition, although the protection rate of vaccine is high in the laboratory, in the field, various factors such as the preservation and transportation of vaccine, injection quality, animal species and other pathogenic diseases will affect the immune effect of vaccine, and it is impossible for any vaccine to obtain 100% immune protection, and vaccine immunization can not effectively eliminate the virus-carrying problem of poultry. Therefore, vaccine immunization is only an expedient measure. In the long run, it is necessary to fundamentally solve the problem, or to completely eliminate the highly pathogenic avian influenza pathogen by comprehensive measures such as biosafety, so as to finally eradicate the disease.
Is vaccination an effective method to control the spread of highly pathogenic avian influenza under the current situation in China? What are its advantages and disadvantages compared with culling?
International experience has proved that vaccination is effective in controlling the spread of highly pathogenic avian influenza. After vaccination against highly pathogenic avian influenza, poultry can gain immune protection by producing antibodies, protecting poultry from avian influenza virus, thus preventing poultry from getting sick. In the current situation of large-scale outbreak, it is necessary to immunize poultry in threatened areas and establish an immune isolation belt. If poultry are not vaccinated, they will not be able to resist the invasion of highly pathogenic avian influenza virus, which will easily lead to new outbreaks and new sources of infection. The quality of vaccine directly affects the effect of immunization, so we should choose the vaccine approved by the state when carrying out immunization, and formulate reasonable immunization procedures to make poultry produce sustained high-level antibodies and protect poultry from getting sick.
At present, poultry within 3 kilometers around the epidemic area are culled in China, and poultry within 5 kilometers outside the epidemic area are taken emergency vaccination measures to control the epidemic of avian influenza. Compared with culling, vaccination can reduce economic losses in the near future. However, when encountering a virulent virus attack, these immunized birds may not show symptoms, but they may form a virus-carrying immunity because the virus cannot be eliminated from the population. Therefore, at the same time, we must also catch culling, which can completely eliminate the source of infection.
What are the good suggestions for the control of waterfowl diseases?
The control of waterfowl diseases is more complicated than that of chickens, pigeons and quails. To control waterfowl disease, firstly, we should disinfect the poultry environment, clean and disinfect the water source; At the same time, waterfowl and chickens should be raised separately, and it is better to keep them on land, as far as possible away from the habitat of wild birds and reduce direct contact with migratory birds. In addition, it is necessary to standardize the supervision of waterfowl breeding and the management of waterfowl market, and strengthen the control of waterfowl diseases through vaccine immunization and strict disinfection.
Four, the identification method of highly pathogenic avian influenza
What is the basis for the final diagnosis of this highly pathogenic avian influenza by the National Avian Influenza Reference Laboratory?
The final diagnosis is based on the isolation and identification of avian influenza virus pathogens from suspected highly pathogenic avian influenza patients, namely:
(1) The titer of 1)H5 hemagglutination inhibition test was above 24, and the agarose diffusion test was positive (except waterfowl).
(2) The highly pathogenic avian influenza virus (N5N1 subtype) was isolated from the samples sent by the epidemic site.
Can an abnormally dead chicken be considered as avian influenza?
At present, there are many diseases that can cause the death of poultry including chickens in China, including avian influenza, Newcastle disease, Marek’s disease, infectious bronchitis, infectious laryngotracheitis, infectious bursal disease, Escherichia coli disease, avian cholera, etc. In addition, other factors such as poisoning or parasites can also lead to the death of poultry. Therefore, it is unscientific to infer avian influenza when poultry die abnormally.
What kinds of serological techniques are used to diagnose avian influenza in China at present?
Which of them are the detection methods specified by OIE? There are mainly hemagglutination test, hemagglutination inhibition test, agar diffusion test, neuraminidase inhibition test, enzyme-linked immunosorbent assay, virus neutralization test and immunofluorescence test. Among them, hemagglutination and hemagglutination inhibition test and agar immunodiffusion test are recommended by OIE.
How to operate and determine the results of hemagglutination and hemagglutination inhibition test?
The specific operation and result judging procedure of hemagglutination (HA) and hemagglutination inhibition (HI) tests are as follows:
(1) Material preparation
A96-hole V-shaped micro-reaction plate, micro-pipette (equipped with dripper). B prepare Alsevers solution and chicken red blood cell suspension. 001mol/L phosphate buffer (PBS) of cpH72. D highly pathogenic avian influenza virus hemagglutinin typing antigen, standard typing serum and negative serum.
(2) Operation method
① Hemagglutination (HA) test (micro method)
A Add 0.025ml PBS into 1~12 holes of the micro reaction plate, and change the dripper.
B Absorb 0025ml of antigen, add it into the first hole, and mix well.
C Suck 0025ml of antigen from the first hole and add it to the second hole, mix it evenly, then suck 0025ml and add it to the third hole, so as to dilute it to the 11th hole, then suck 0025ml from the 11th hole and discard it, and change the dripper.
D Add 0.025ml PBS to each well.
E Add 0.025ml 1%(V/V) chicken red blood cell suspension to each well (shake the chicken red blood cell suspension thoroughly before adding).
F Shake and mix well, and let it stand at room temperature (20~25℃) for 40 minutes and then observe the results (if the ambient temperature is too high, it can be placed at 4℃ for 1 hour). The red blood cells in the control hole will sink to the bottom of the hole in an obvious button shape.
G result judgment. Tilt the plate and observe whether the red blood cells flow in the form of tears. A fully hemagglutinated antigen or virus with the highest dilution ratio represents a hemagglutination unit (HAU).
② Hemagglutination inhibition (HI) test (micro method)
A according to the results of hemagglutination test, the virus antigen of 4HAU was prepared. The highest dilution multiple of the completely hemagglutinated virus is taken as the end point, and the dilution multiple of the antigen containing 4HAU is divided by 4. For example, if the terminal titer of hemagglutination is 1∶256, the dilution multiple of 4HAU antigen should be 1∶64(256 divided by 4).
B add 0.025ml PBS to wells 1~11 of the micro reaction plate, and add 0.05ml PBS to the 12th well.
C Suck 0.025ml of serum into the first hole, mix it thoroughly, suck 0.025ml into the second hole, dilute it to the 10th hole in turn, and suck 0.025ml from the 10th hole and discard it.
Add 0025ml of virus antigen solution containing 4HAU into holes D1 ~ 11, and let it stand at room temperature (about 20℃) for at least 30min.
E Add 0.025ml of chicken red blood cell suspension into each well, mix it gently, and let it stand for about 40min (room temperature is about 20℃, and if the ambient temperature is too high, it can be kept at 4℃ for 1h), and the control red blood cells will sink to the bottom of the well in an obvious button shape.
(3) Results The highest dilution multiple of serum that completely inhibited four HAU antigens was determined as the HI titer.
The test results are valid only if the serum titer of negative control hole is not more than 2log2 and the serum error of positive control hole is not more than 1 titer. The HI value is less than or equal to 3log2 to determine that the HI test is negative; The HI value is equal to 4log2, which is positive.
How to operate and determine the results of AGID test?
The specific operation and result judging procedure of agar diffusion test are as follows:
(1) Material preparation
① Thiomersal solution, 0.01mol/L PBS solution with pH of 72.
② Making agar plates.
③ Avian influenza agar gel immunodiffusion antigen, standard negative and positive serum.
(2) Operation method
① Punch holes. Punch holes in the prepared agar plate according to a group of 7 holes (1 hole in the middle and 6 holes around), with a hole diameter of about 5 mm and a hole spacing of 2~5 mm. Insert the agar in the holes upward from the right edge with the inclined plane of No.8 needle, and gently pick out the agar to the left, so as not to damage the edge or make the agar layer separate from the bottom of the dish.
② Back cover. Lightly bake the bottom of the dish with alcohol lamp until the agar just melts, and close the bottom of the hole to prevent side leakage.
③ Add samples. Use a micropipette or a 025ml syringe with 6~7 needles to suck antigen suspension and drop it into the middle hole (No.7 in the next page), add standard positive serum into the peripheral holes ① and ④ respectively, and add the detected serum into the other four peripheral holes (No.2, ③, ⑤ and ⑤ in the next page) according to the numbered order. Each hole should be filled to prevent overflow, and a dripper should be changed for each sample added.
4 role. After adding the sample, let it stand for 5~10 minutes, then put the plate upside down and put it in a wet box, and let it act in a 37℃ incubator. Observe and record the results at 24 hours, 48 hours and 72 hours respectively.
(3) Determination of results
(1) determination method. Observe the agar plate under fluorescent lamp or side strong light. If there is a clear white precipitation line between the standard positive serum (holes ① and ④ in the figure) and the antigen hole, the test is established.
② Criteria for judging
A If a clear and dense precipitation line appears between the detected serum hole (No.② in the figure) and the central antigen hole, and the line coincides with the end of the precipitation line between antigen and standard positive serum, the detected serum is judged as positive.
B Although there is no precipitation line between the detected serum hole (No.③ in the figure) and the central hole, but one end of the precipitation line of the standard positive serum hole (No.④ in the figure) is bent towards the inside of the detected serum hole, the detected sample of this hole is judged as weak positive (all weak positive samples should be repeated, and those who are still weak positive are judged as positive).
C If there is no precipitation line between the detected serum hole (No.5 in the figure) and the central hole, and the standard positive serum precipitation line goes straight to the detected serum hole, the detected serum is judged as negative.
D The precipitation line between the detected serum hole (No.6 in the figure) and the central antigen hole is thick and turbid, or the precipitation line between the standard positive serum and the antigen hole crosses and stretches straight. The detected serum hole is nonspecific and should be redone. If nonspecific reaction still occurs, it will be judged as negative.
What are the diagnostic criteria for determining highly pathogenic avian influenza?
Diagnostic indicators mainly include the following three aspects:
(1) Clinical diagnostic indicators
① Acute onset and death; ② Bleeding of foot scales; ③ bleeding or cyanosis of cockscomb and edema of head; ④ Extensive and severe bleeding in muscles and other tissues and organs.
(2) Serological diagnostic indicators
① The hemagglutination inhibition (HI) titer of H5 or H7 reaches 24 or above; ② Avian influenza agar immunodiffusion (AGP) test was positive (except waterfowl).
(3) Etiological diagnostic indicators
①H5 or H7 subtype virus was isolated positively; ② H5 or H7 specific molecular biology diagnosis was positive; ③ The pathogenicity index (IVPI) of intravenous inoculation of any subtype virus is greater than 12.
According to the above diagnostic indicators, the result judgment includes the following three aspects:
(1) The clinically suspected highly pathogenic avian influenza conforms to the clinical diagnosis index 1, and has at least one of the clinical diagnosis indexes 2, 3 and 4.
(2) The suspected highly pathogenic avian influenza conforms to the result judgment (1) and the serological diagnosis index ① or/and ②.
(3) The diagnosis conforms to the result judgment (2) and at least conforms to one of the etiological diagnosis indexes ①, ② and ③.
Is highly pathogenic avian influenza a chicken plague or Newcastle disease that has appeared before in China?
How should they be distinguished? Recently, the highly pathogenic avian influenza caused by H5N1 subtype avian influenza virus in China is not the chicken plague that appeared in China before. The academic name of chicken plague is Newcastle disease, which was found in a place called Xincheng in England in 1926. Therefore, it is called Newcastle disease, and its incidence and mortality are also very high, which has caused great harm to the chicken industry in China. However, there are good vaccines to control Newcastle disease in China, so the disease still occurs in some places in rural areas. Due to vaccination in large-scale chicken farms, if the vaccine is properly vaccinated, the incidence and mortality are very low, and its harm degree is much lighter than that of avian influenza. Highly pathogenic avian influenza has no specific clinical symptoms, which is characterized by sudden onset, loss of appetite, sudden rise of body temperature, high mental depression, edema and cyanosis of comb and wattle, accompanied by a large number of deaths, and the mortality rate can reach more than 90% within a few days. Newcastle disease and avian influenza are obviously different, and their pathogens are completely different viruses. Avian influenza virus is orthomyxovirus and Newcastle disease virus is paramyxovirus. Typical clinical symptoms can be seen in the early stage of Newcastle disease virus infection: long incubation period, respiratory symptoms, diarrhea, loss of appetite, mental fatigue, and neurological symptoms in the later stage. Under the current breeding conditions, typical Newcastle disease rarely occurs in chickens immunized with Newcastle disease vaccine, and infected chickens generally show mild respiratory symptoms, neurological symptoms and decreased egg production of laying hens, with low mortality.
Five, the correct treatment of highly pathogenic avian influenza
Is it possible for highly pathogenic avian influenza virus to spread vertically through eggs after it infects chickens?
The transmission of highly pathogenic avian influenza among birds mainly depends on horizontal transmission. The virus was isolated from the trachea and cloacal swabs of infected birds, indicating that the virus can be transmitted through aerosol or feces pollution. At present, the incubation period of highly pathogenic avian influenza prevalent in China is very short, and a large number of poultry die with almost no clinical symptoms. Usually, once poultry are infected with highly pathogenic avian influenza virus, the laying rate drops sharply, and most chickens with highly pathogenic avian influenza die before laying eggs. Moreover, once the epidemic situation is discovered, all sick birds and susceptible birds in the epidemic area are culled and treated harmlessly, and the possibility of containing avian influenza virus in eggs is very small. The authoritative textbook Avian Diseases holds that there is no evidence that highly pathogenic avian influenza virus will spread vertically. Although it has been reported that avian influenza virus was found in the eggs laid by chickens infected by humans in the laboratory, the resistance of avian influenza virus is not strong, and it is not difficult to inactivate the virus itself. Cooked eggs killed all pathogens. If the chicken embryo is infected by avian influenza virus, it is impossible for the chicken embryo to survive during the incubation period, and the possibility of vertical transmission through chicks is extremely small.
Is the avian influenza virus directly transmitted to people through poultry?
Judging from the current situation in China, avian influenza virus only spreads among birds, and the phenomenon that chickens directly transmit influenza virus to people and cause illness has not yet occurred in various epidemic areas in China. In all epidemic places in China, the health department has carried out medical examination and observation on people who are in close contact with sick birds, and no infection has been found. So far, no cases of human infection with avian influenza have been found in other Asian countries, such as Japan, South Korea, the Philippines and Malaysia. In Vietnam and Thailand, avian influenza virus H5N1 has been isolated from dead people, and the exact mechanism remains to be studied. The World Health Organization announced on February 12 that the test results of Vietnamese deaths also showed that the avian influenza virus did not spread from person to person.
Will consumers affect people’s health after eating poultry vaccinated with avian influenza?
No. Because we injected an inactivated vaccine, it is not infectious. Food safety problems caused by adjuvants can be solved by determining the vaccination time before slaughter. According to the regulations, vaccination was stopped 28 days before slaughter, and the vaccine adjuvant was absorbed in the body at the time of slaughter, so the quality of ketone bodies and human health would not be affected by the use of avian influenza vaccine.
Can the dead chickens be eaten after high-temperature processing?
Generally speaking, the cause of death of many sick chickens is unclear. Although the pathogen can be killed after high-temperature processing, it is difficult to become safe after high-temperature processing for some heat-resistant toxins or deaths caused by excessive drugs, especially for some chickens that have deteriorated after death, which is more harmful to people after eating. Therefore, chickens that have died of illness, especially those with unknown etiology, are just inedible.
How should the staff directly involved in killing birds do personal protection?
(1) Wear appropriate protective clothing.
(1) wear protective clothing, or wear long-sleeved surgical gown and a waterproof apron. ② Wear sterilized rubber gloves. ③ Wear N95 mask or standard surgical mask. ④ Wear goggles. ⑤ Wear sterilized rubber boots or disposable shoe covers.
(2) Hand washing and disinfection
(1) close contact with infected birds, wash your hands with soap.
(2) poultry culling and transport personnel after the operation, to wash their hands with disinfectant.
(3) Health monitoring
① All personnel exposed to infected birds and suspicious poultry farms shall be monitored by the health department.
② The culling personnel and poultry farm workers with symptoms of respiratory infection should be inspected by the health department as soon as possible.
(3) The family members of the above-mentioned personnel should also receive health monitoring.
④ People with low immune function, over 60 years old and chronic heart and lung diseases should avoid working in contact with poultry.
⑤ Relevant personnel and veterinarians should accept serological monitoring.
How should the reporters who go to the epidemic area do well in protection?
(1) Need to prepare articles such as masks, latex gloves, protective clothing, disposable hats or hoods, rubber boots, alcohol cotton balls or sterilized paper towels, and large plastic bags for treating pollutants.
(2) Protection requirements
(1) to wear masks, masks shall not be used cross, used masks shall not be discarded at will.
② Protective clothing must be worn.
③ Rubber boots must be worn when entering places polluted by poultry, and they should be cleaned and disinfected after use.
④ Wash or wipe hands after taking off personal protective equipment.
⑤ If possible, you should take a bath, especially in places with poultry manure and dust.
⑥ Waste should be put into plastic bags and placed in designated places. Six, highly pathogenic avian influenza prevention and control related knowledge
What is zoonosis? What are the common zoonotic diseases?
Zoonosis: Diseases and infections naturally transmitted between humans and vertebrates. Its pathogens include viruses, bacteria, mycoplasma, spirochetes, rickettsia, chlamydia, fungi, parasites and so on. The main diseases are anthrax, plague, swine erysipelas, swine vesicular disease, rabies, brucellosis, tuberculosis, listeriosis, streptococcosis, leptospirosis, trichinosis and Fasciola hepatica. Zoonosis can be transmitted through contact, eating meat or other means. Sick livestock, fur, blood, feces, bones, carcasses, sewage, etc., often carry all kinds of germs, viruses and parasites, eggs, etc., which will be transmitted to people if not handled well.
What are the main contents of the emergency plan for handling highly pathogenic avian influenza in China?
In order to ensure the timely, rapid, efficient and orderly handling of highly pathogenic avian influenza epidemic, protect the sustained and healthy development of animal husbandry in China, safeguard people’s health and maintain social stability, an emergency plan for handling highly pathogenic avian influenza was formulated according to the Law of People’s Republic of China (PRC) on Animal Epidemic Prevention, the Law of People’s Republic of China (PRC) on the Prevention and Control of Infectious Diseases and other laws and regulations.
The main contents of this plan include:
(1) Establish an emergency command system, and define the functions and powers;
(2) the confirmation, classification and identification of epidemic situation and the determination of the conditions for starting the plan;
(3) emergency response mechanism, including the general procedures of epidemic response and emergency measures at all levels;
(4) Clarify the specific responsibilities of governments and departments at all levels;
(5) Establish safeguard measures, including material guarantee, financial guarantee, technical guarantee and personnel guarantee, and establish epidemic notification mechanism, information exchange system and on-site simulation exercise;
(6) Other related matters, etc.
How does OIE classify animal diseases? How is China divided?
According to the harm degree of diseases to animal health and human public health, the World Organization for Animal Health divides animal diseases into two types: A and B.
Class A diseases include: foot-and-mouth disease, swine fever, highly pathogenic avian influenza and Newcastle disease.
Class B diseases include: anthrax, brucellosis, bovine tuberculosis, rabies and other zoonotic diseases and non-virulent animal diseases.
China’s "People’s Republic of China (PRC) Animal Epidemic Prevention Law" divides animal diseases into the following three categories according to the harm degree of animal diseases to aquaculture production and human health: the first category of diseases refers to those that are seriously harmful to people and animals and need to take urgent and severe compulsory prevention, control and extermination measures; Class II epidemics refer to those that can cause great economic losses and need to take strict control and extermination measures to prevent their spread; Three kinds of epidemics refer to those that are common and frequent, may cause great economic losses and need to be controlled and purified.
What diseases are the first, second and third types of animal diseases defined by China?
The specific list of these diseases is as follows:
A kind of animal epidemic disease
Foot-and-mouth disease, pig vesicular disease, swine fever, African swine fever, African horse plague, bovine contagious pleuropneumonia, bovine spongiform encephalopathy, pruritus, bluetongue disease, peste des petits ruminants, sheep pox and goat pox, avian influenza (highly pathogenic avian influenza) and Newcastle disease.
Second-class animal diseases
(1) zoonotic diseases include pseudorabies, rabies, anthrax, Clostridium welchii, paratuberculosis, brucellosis, toxoplasmosis, echinococcosis and leptospirosis.
(2) bovine infectious rhinotracheitis, moderate and malignant catarrhal fever, bovine leukemia, bovine hemorrhagic septicemia, bovine tuberculosis, bovine coke disease, bovine trypanosomiasis and schistosomiasis japonica.
(3) Sheep and goat diseases: goat arthritis encephalitis, Medina’s disease.
(4) Swine disease, porcine encephalitis B, porcine parvovirus disease, porcine reproductive and respiratory syndrome, swine erysipelas, swine pneumonitis, swine streptococcosis, porcine infectious atrophic rhinitis, swine mycoplasma pneumonia, trichinosis and swine cysticercosis.
(5) Equine infectious anemia, equine melioration, equine epidemic lymphangitis and trypanosomiasis evansi.
(6) Infectious laryngotracheitis, infectious bronchitis, infectious bursal disease, Marek’s disease, egg drop syndrome, avian leukemia, avian pox, duck plague, duck viral hepatitis, gosling plague, avian cholera, pullorum, mycoplasma gallisepticum infection and coccidiosis.
(7) Rabbit disease Rabbit viral hemorrhagic disease, rabbit myxomatosis, rabbit fever and rabbit coccidiosis.
(8) Aquatic animal diseases, viral hemorrhagic septicemia, carp viremia and shrimp baculovirus disease.
(9) Bee disease: American larval putrefaction disease, European larval putrefaction disease, bee sporidiosis, bee acariasis, bee acariasis and chalk disease.
Three kinds of animal diseases
(1) zoonotic diseases such as black leg disease, listeriosis, melioidosis, actinomycosis, Fasciola hepatica and filariasis.
(2) Bovine disease, bovine epidemic fever, bovine viral diarrhea/mucosal disease, bovine genital campylobacter disease, trichomoniasis and bovine myiasis.
(3) Sheep and goats suffer from pulmonary adenomatosis, sheep endemic abortion, infectious pustular dermatitis, hoof rot, infectious ophthalmia, enterotoxemia, caseous lymphadenitis and sheep scabies.
(4) equine influenza, equine adenopathy, equine nasal pneumonia, ulcerative lymphangitis and equine plague.
(5) Swine diseases, transmissible gastroenteritis, paratyphoid fever and treponema suis dysentery.
(6) Avian disease viral arthritis, avian infectious encephalomyelitis, infectious rhinitis, avian tuberculosis and avian typhoid fever.
(7) Infectious hematopoiesis necrosis and gill mold in fish with fish diseases.
(8) Other animal diseases are mink Aleutian disease, mink viral enteritis, velvet antler mycosis, silkworm polyhedrosis, silkworm white stiff disease, canine distemper and leishmaniasis.
Why should China inform FAO, WHO and neighboring countries and regions of the avian influenza epidemic in time?
Major animal diseases are not only related to the development of animal husbandry, but also closely related to human health, and also related to the development of animal husbandry in neighboring countries and regions. Therefore, it is necessary to inform FAO, WHO and neighboring countries and regions of the epidemic situation of avian influenza in China in time. This fully demonstrates China’s determination to completely control related epidemics, and also shows the highly responsible spirit of our government, so as to better join hands to jointly prevent avian influenza and gain the understanding and support of the international community.
What kind of international organizations are WHO, FAO and OIE?
What are the specific functions? WHO is the abbreviation of the World Health Organization and a specialized agency under the United Nations, which was established on April 7, 1948. Headquartered in Geneva, Switzerland. The purpose of the World Health Organization is to enable people all over the world to obtain the highest possible level of health. The organization defines health as "the perfect state in physical, mental and social life". The main functions of the World Health Organization include: promoting the prevention and treatment of epidemic and endemic diseases; To provide and improve teaching and training in public health, disease treatment and related matters; Promote the determination of international standards for biological products. As of May 2003, the World Health Organization has 192 member countries.
FAO is the abbreviation of the Food and Agriculture Organization of the United Nations, which was established on October 16th, 1945. Headquartered in Rome, Italy. The aim of FAO is to improve the nutritional level and living standard of the people in member countries by strengthening the actions of countries around the world and the international community; Improve the production and distribution efficiency of all agricultural products; Improve the situation of rural population; Promote the development of the world economy and ensure that human beings are free from hunger. The organization’s business scope is quite extensive, including agriculture, forestry, animal husbandry, fishery production, science and technology, policy and economy. It collects, sorts out, analyzes and disseminates information about food and agriculture production and trade to all countries in the world; Providing technical assistance to member States; Mobilize the international community to invest in agriculture and use its technological advantages to implement agricultural development projects of international development and financial institutions; Providing advisory services to member countries on policies and plans for agriculture and food; Discuss major issues in the field of international food and agriculture, formulate relevant international codes of conduct and regulations, and strengthen consultation and cooperation among members. There are 174 member countries, one member organization (EU) and one associate member country.
OIE is the abbreviation of the World Organization for Animal Health. The organization was formally established on January 25, 1924. Since its establishment, OIE has established its main objectives as an international organization for animal health, that is, to promote and coordinate international cooperative experiments and research on the causes and control of animal infectious diseases; Collect animal epidemic information and control measures and draw the attention of the government and its animal health organizations; Review the draft agreement on animal disease control laws and regulations, and provide supervision and implementation measures to member States. There are currently 143 member States.
Prepared by the expert group of the Ministry of Agriculture
Published by China Agricultural Publishing House