Questions and Answers on Prevention and Control of Highly Pathogenic Avian Influenza
First, the concept, incidence and epidemic characteristics of highly pathogenic avian influenza
1. What is avian influenza? What is highly pathogenic avian influenza?
Avian influenza is the abbreviation of avian influenza, and it is an infectious disease of poultry (poultry and wild birds) caused by influenza A virus. Avian influenza virus infection can show mild respiratory symptoms and digestive symptoms, and the mortality rate is low; Or manifested as more serious systemic, hemorrhagic and septic symptoms, and the mortality rate was higher. This difference in symptoms is mainly determined by the virulence of avian influenza virus.
According to the pathogenicity and virulence of avian influenza virus, avian influenza can be divided into highly pathogenic avian influenza, low pathogenic avian influenza and non-pathogenic avian influenza. There are different subtypes of avian influenza virus. The diseases caused by H5 and H7 subtype strains (represented by H5N1 and H7N7) are called highly pathogenic avian influenza (HPAI). Recently, avian influenza caused by H5N1 subtype at home and abroad is highly pathogenic avian influenza, with high morbidity and mortality and great harm.
2. How long is the incubation period of highly pathogenic avian influenza? Can it be contagious during the incubation period?
The incubation period of avian influenza ranges from several hours to several days, and the longest is 21 days. The incubation period is influenced by many factors, such as virus virulence, infected virus amount, resistance of poultry, age and breed, feeding management, nutritional status, environmental sanitation and stress factors. Highly pathogenic avian influenza has short incubation period, rapid onset and high morbidity and mortality. There is the possibility of infection during the incubation period.
3. What is the transmission route of avian influenza?
There are two kinds of transmission of avian influenza: direct contact between sick birds and healthy birds and indirect contact with virus pollutants. Avian influenza virus exists in the digestive tract, respiratory tract and organs of sick and infected birds. Therefore, the virus can be excreted with eye, nose, oral secretions and feces, and any objects contaminated by virus-containing secretions, feces and dead poultry carcasses, such as feed, drinking water, chicken coops, air, cages, feeding management appliances, transport vehicles, insects and various birds carrying viruses, can spread mechanically. Healthy birds can be infected through respiratory tract and digestive tract, causing illness. Avian influenza virus can spread through the air, and the migration of migratory birds (such as wild ducks) can spread avian influenza virus from one place to another, and it can cause infection and illness of birds through polluted environment (such as water source). The circulation of poultry flocks and poultry products with avian influenza virus can cause the spread of avian influenza.
4. What are the main clinical manifestations of highly pathogenic avian influenza? What is the difference with Newcastle disease?
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 orthomyxoviridae, and Newcastle disease virus is paramyxoviridae. Typical clinical symptoms of Newcastle disease virus infection can be seen in the early stage: long incubation period, respiratory symptoms, diarrhea, loss of appetite, mental fatigue, and neurological symptoms in the later stage. Under the current breeding conditions, chickens immunized with Newcastle disease vaccine will not have typical Newcastle disease, and infected chickens generally show mild respiratory symptoms, neurological symptoms and decreased egg production of laying hens, with low mortality.
5. What are the epidemic characteristics of highly pathogenic avian influenza?
Highly pathogenic avian influenza can be prevalent all year round, but it occurs frequently in winter and spring because the avian influenza virus has strong resistance at low temperature. All kinds of birds with different ages can be infected with highly pathogenic avian influenza, which has an acute onset and rapid spread, and its mortality rate can reach 100%.
6. Is the occurrence of highly pathogenic avian influenza related to the age, sex and variety of poultry?
Many poultry, such as chickens, turkeys, guinea fowl, quails, ducks and geese, can be infected, but chickens, turkeys, ducks and geese are more common, and turkeys and chickens are the most susceptible, with high morbidity and mortality. Waterfowl such as ducks and geese have low susceptibility, but they can be infected with virus or recessive infection, and sometimes cause a large number of deaths. Chickens and turkeys of various breeds and different ages can be infected and die, but the mortality rate of waterfowl such as ducklings and goslings is higher. It has not been found that the occurrence of highly pathogenic avian influenza is related to the sex of poultry.
7. Will highly pathogenic avian influenza spread through eggs?
The transmission of highly pathogenic avian influenza among flocks mainly depends on horizontal transmission, such as air, feces, feed and drinking water. The current evidence shows that highly pathogenic avian influenza will not be transmitted through eggs. However, experiments show that the eggs of infected chickens contain influenza virus, so the possibility of vertical transmission cannot be completely ruled out. The fertilization rate and hatching rate of infected and diseased chickens decreased, so they could not be used for hatching.
8. Why do highly pathogenic avian influenza occur in winter and spring?
Highly pathogenic avian influenza can occur all year round, but it occurs frequently in winter and spring. The main reasons are:
First, the avian influenza virus is sensitive to temperature. With the increase of environmental temperature, the survival time of the virus is shortened. In addition, the light intensity is relatively higher in summer and autumn, and the ultraviolet rays in the sun have a strong killing effect on the virus.
Secondly, the ventilation intensity of poultry houses in summer and autumn is much higher than that in winter and spring. Good ventilation can greatly reduce the number of viruses in the environment of chicken houses. Therefore, the chances and number of viruses invading chickens are obviously reduced, and the probability of infection is reduced. At the same time, good ventilation also reduces the stimulation of bad gas to the respiratory mucosa of chickens, which is of great significance to maintain the resistance of respiratory mucosa.
II. Measures to Prevent and Control Highly Pathogenic Avian Influenza
9. Is there a vaccine to prevent highly pathogenic avian influenza?
China has successfully developed a vaccine to prevent H5N1 highly pathogenic avian influenza. Farms in non-epidemic areas should be vaccinated in time to prevent the occurrence of avian influenza.
10. Should highly pathogenic avian influenza be treated?
When highly pathogenic avian influenza occurs in poultry, there is no good treatment at present because of its acute onset, high incidence and high mortality. According to national regulations, all birds within three kilometers should be culled and buried immediately after being diagnosed as highly pathogenic avian influenza, and their pollutants should be treated harmlessly. In this way, the epidemic situation can be put out as soon as possible, the source of infection can be eliminated, and economic losses can be reduced. It is one of the effective means to put out bird flu and should be resolutely implemented.
11. How to disinfect poultry houses, pollutants and their environment with highly pathogenic avian influenza?
Influenza virus can pollute poultry houses, cages, padding and so on with the excretion of feces and nasal secretions from infected birds. Influenza virus is sensitive to disinfectants and heat. When the polluted poultry house is disinfected, it must be cleaned with detergent to remove dirt, then disinfected with sodium hypochlorite solution, and finally fumigated with formalin and potassium permanganate. Iron cages can also be disinfected by flame. Due to the high virus content in feces, special attention should be paid to the treatment. Feces and bedding should be disposed of by burying, and the tools used to treat them should be soaked in caustic soda water or other disinfectants for disinfection.
12. Which disinfectants can effectively kill avian influenza virus? How to use it?
Avian influenza virus has poor survival ability in the external environment. As long as proper disinfection measures are taken, disinfectants commonly used in poultry production practice, such as aldehydes, chlorine-containing disinfectants, phenols, oxidants and alkalis, can kill the virus in the environment. The disinfection effect of the following disinfectants in the field environment is better:
(1) Formaldehyde disinfectants include formaldehyde and polyformaldehyde, among which formaldehyde fumigation is the most commonly used. Closed pens can be fumigated and disinfected by adding 14 ~ 42 ml of formalin to 7 ~ 21 g of potassium permanganate per cubic meter. When fumigating and disinfecting, the room temperature should generally not be lower than 15℃ and the relative humidity should be 60% ~ 80%. Potassium permanganate can be added to the container first, then formalin solution can be added, and the disinfection purpose can be achieved by sealing the doors and windows for more than 7 hours, and then opening the doors and windows for ventilation and eliminating the residual odor.
⑵ The disinfection effect of chlorine-containing disinfectants depends on the content of available chlorine. The higher the content, the stronger the disinfection ability, including inorganic chlorine-containing disinfectants and organic chlorine-containing disinfectants. 5% bleaching powder solution can be sprayed on animal pens, cages, feeding troughs and vehicles for disinfection. Hypochloric acid is quick in disinfection and has no residue and odor, so it is often used for disinfection of equipment and countertops in food factories and slaughterhouses.
(3) Alkaline preparations mainly include sodium hydroxide, etc. Most of the sodium hydroxide preparations used for disinfection are crude alkali liquor containing 94% sodium hydroxide, which is often heated to prepare 1% ~ 2% aqueous solution for disinfection of chicken coops, walls, sports fields and dirt contaminated by viruses, and also for disinfection of slaughterhouses, food factories and other floors, transportation vehicles and other items. After spraying for 6~12 hours, rinse with clear water.
13. Will the co-culture of chickens, ducks, geese and pigs lead to the occurrence of highly pathogenic avian influenza?
Poultry should not be mixed with pigs, because the flu virus of poultry can infect pigs, and the flu virus of human can also infect pigs. Because influenza virus has eight different nucleic acid fragments, when these two different virus particles infect a cell together, their nucleic acid fragments will recombine and arrange to produce new influenza virus particles, which can often form a big epidemic for human beings and cause great harm.
In addition, chickens should not be mixed with ducks, geese and other waterfowl, because the carrying rate of various subtypes of influenza virus in waterfowl is very high, and some of them do not show any clinical symptoms. After the virus in their feces infects chickens, it can cause the occurrence and epidemic of avian influenza, resulting in serious economic losses.
14. Is it useful to strengthen the management of poultry breeding to prevent avian influenza?
Strengthening feeding management is a prerequisite to prevent all animal infectious diseases. Only under good feeding management can poultry be guaranteed to be in the best growth state and have good disease resistance. From the perspective of bird flu prevention, we must consider feeding management and disease prevention as a whole, and take strict management measures, such as isolation of farms and houses, environmental disinfection, and control of the flow of people and articles, to prevent birds from being harmed by other diseases.
15. How to prevent highly pathogenic avian influenza?
Comprehensive preventive measures must be taken to prevent avian influenza. The farm is far away from residential areas, bazaars, traffic arteries and other animal production sites and related facilities; Do not introduce breeding eggs and poultry from epidemic areas; Strictly disinfect passing vehicles and the surrounding environment, incubation hall, incubator, coop cage, staff’s clothes and shoes, etc. Adopt the feeding mode of all-in and all-out to prevent the contact between birds and poultry; In the farm, there should be a special passage for the staff to go in and out, and the staff and their routine protective articles should be cleaned and disinfected reliably; It is strictly forbidden for all outsiders to enter or visit the animal farm area. In areas threatened by highly pathogenic avian influenza, vaccination should be carried out under the guidance of the local veterinary health management department, and serological monitoring should be carried out regularly to ensure that the immune prevention effect of the vaccine is reliable.
16. How can hatcheries and hatcheries prevent highly pathogenic avian influenza?
First of all, the design of the incubator should be done well. Should be done from the egg room, egg tray, hatching, hatching, waiting room and 1-day-old chick loading room to the transport area should be a one-way traffic route. Each incubator must be conducive to thorough cleaning and disinfection, and the ventilation system should be able to prevent the re-circulation of polluted air and dust.
Second, do a good job in the inspection and timely disinfection of breeding eggs. Breeders should collect eggs regularly after laying, and remove the dirt on the surface in time to eliminate the eggs that are seriously polluted and cracked.
Third, do a good job of cleaning and disinfecting the incubator, egg tray for hatching, breeding eggs and hatcher before hatching.
Fourth, thoroughly disinfect the vehicles and equipment for transporting young chicks to prevent cross-infection.
Fifth, under the guidance of the local veterinary health management department, the breeder chickens are immunized, and the chicks are also vaccinated.
17. Is there any relationship between the poultry breeding methods and highly pathogenic avian influenza?
Feeding methods are closely related to the occurrence and control of avian influenza, and good feeding management conditions are the key to prevent avian influenza.
It is necessary to avoid the mixed culture of chickens and waterfowl, because waterfowl is one of the important storage hosts of avian influenza virus, which can carry the virus without necessarily getting sick, but it can excrete the virus through feces and pollute the water source or environment. These viruses may infect chickens and other poultry raised at the same time, resulting in their illness.
Grazing or stocking poultry are more likely to get in touch with other poultry, migratory birds or the environment, feed and drinking water polluted by these wild animals, and the probability of being infected with avian influenza is greatly increased.
Intensive poultry are less likely to be infected with avian influenza because of good environmental isolation conditions, strict control of personnel and logistics, and good veterinary health and epidemic prevention measures, and once it happens, control measures can be taken quickly.
18. What is the recommended immunization program for highly pathogenic avian influenza?
Once the epidemic occurs, all susceptible birds within 5 kilometers around the epidemic area must be vaccinated urgently, and at the same time, an immune isolation belt should be established around the epidemic area. Vaccination is only used for healthy chickens that have not been infected with highly pathogenic avian influenza virus. Breeding chickens and commercial laying hens should generally be vaccinated for 2~3 times. Emergency immunization must be carried out under the guidance of veterinary personnel.
19. Can birds with highly pathogenic avian influenza heal themselves?
I can’t. When highly pathogenic avian influenza virus infects, the morbidity and mortality can reach 100%.
20. Why should all poultry be culled within a radius of 3 kilometers around the highly pathogenic avian influenza epidemic?
In China, the radius of 3 km around the epidemic spot of highly pathogenic avian influenza is classified as an epidemic area, because the poultry within the radius of 3 km around the epidemic spot are the most susceptible to infection. In order to ensure that the epidemic situation of highly pathogenic avian influenza can be completely and thoroughly extinguished, it is absolutely necessary to cull all the poultry around the epidemic spot and its 3 km. This will help to control the spread of pathogens caused by sick birds and their feces, sewage and other pollution sources. This is the most effective way to control severe infectious diseases, and it is also an international practice.
21. Why should culled poultry be treated harmlessly?
Because culled poultry may contain highly pathogenic avian influenza virus, if these pathogens are not eradicated and the sick birds are allowed to spread into the market, it will inevitably lead to the spread of highly pathogenic avian influenza virus and may endanger the health of consumers. In order to ensure the health of consumers and effectively control the epidemic diseases, the culled poultry must be incinerated and buried harmlessly.
22. Why should the epidemic areas of highly pathogenic avian influenza be blocked?
Isolate and block the highly pathogenic avian influenza epidemic area as soon as possible, so as to limit the flow of poultry, personnel and transport vehicles, so as to prevent the highly pathogenic influenza virus from spreading from the epidemic area to the non-epidemic area, prevent the epidemic from further expanding, and reduce the major economic losses and international impact caused by highly pathogenic avian influenza.
23. When a highly pathogenic avian influenza occurs, why should the focus be tracked?
Because it is the key to control highly pathogenic avian influenza to eliminate the epidemic source in time and thoroughly. When highly pathogenic avian influenza occurs, the epidemic situation should be reported in time, and the epidemic point can be found as soon as possible, so that the epidemic point can be blocked in a short time and poultry can be culled, which can effectively prevent the spread and spread of avian influenza epidemic.
24. What is the time limit for lifting the blockade?
The longest incubation period of avian influenza is 21 days, and new cases of avian influenza virus infection may occur at any time during the incubation period. Only when there are no new cases of infection in the incubation period, can it be proved that there is no avian influenza virus in the blocked area, and after the blockade is lifted, it can be guaranteed that there will be no new outbreak of highly pathogenic influenza in this area, so as to achieve the purpose of extinguishing the epidemic. Therefore, the blockade of the epidemic area with highly pathogenic avian influenza epidemic can only be lifted after the last poultry is culled for at least one incubation period.
25. What are the criteria for putting out an outbreak?
The standard for putting out an outbreak is: after culling the last cases in the outbreak area and thorough disinfection, no new cases of avian influenza appear for at least 21 days, indicating that the outbreak in this area has been put out.
26. Why should we monitor the epidemic situation of migratory birds?
Avian influenza virus can infect many kinds of wild birds, especially migratory waterfowl. Evidence has shown that migratory birds are often the real source of the spread of avian influenza pathogens. Therefore, it is very useful to strengthen the epidemic monitoring of migratory birds to find the epidemic source of avian influenza. The large-scale and simultaneous outbreak of avian influenza in many countries in Asia is not unrelated to the migration of migratory birds.
27. How can chickens and ducks raised by farmers on a small scale prevent bird flu?
We should pay attention to the cleanliness and hygiene of poultry houses, disinfect poultry houses regularly, and consciously accept the monitoring of supervising agencies for animal epidemic prevention. If you are in the threatened area of avian influenza, you should give effective vaccines to chickens and ducks. Once a suspected highly pathogenic avian influenza epidemic situation is found, it should be reported to the local supervising agency for animal epidemic prevention immediately, and measures should be taken to block and isolate the epidemic spots to prevent the epidemic from spreading.
Third, the identification method of highly pathogenic avian influenza
28. At present, what are the research results of highly pathogenic avian influenza?
Since the mid-1990s, China has done a lot of work on the epidemiology, diagnosis, immune control and basic research of avian influenza, and obtained many research results. The diagnosis technology of avian influenza has been established: (1) Agar diffusion (AGP) diagnosis technology. (2) subtype typing technology of avian influenza virus. (3) Virus molecular diagnosis and detection technology. Avian influenza vaccine development: An inactivated vaccine of H5 subtype avian influenza has been developed, which can be used for emergency immunization of H5 subtype highly pathogenic avian influenza. The live carrier vaccine of H5N1 subtype avian influenza recombinant fowlpox virus has also entered the stage of environmental release and safety evaluation.
29. How long will it take to confirm the pathogen? Do what experiment?
Highly pathogenic avian influenza must be diagnosed by virus isolation and identification. It usually takes at least 3~5 days for virus isolation and subtype identification. The pathogenicity of the virus must be finally determined by artificial intravenous inoculation of non-specific pathogen chickens (SPF chickens).
30. What are the criteria for the diagnosis of highly pathogenic avian influenza stipulated in the technical specifications for the prevention and control of highly pathogenic avian influenza issued by the Ministry of Agriculture?
According to the Notice of the Ministry of Agriculture on Printing and Distributing Seven Technical Specifications for Prevention and Control of Highly Pathogenic Avian Influenza (Nongbanmu [2002] No.74), it can be confirmed that highly pathogenic avian influenza has occurred under the following circumstances: (1) It has typical clinical symptoms and pathological changes, acute onset and high mortality, and can exclude Newcastle disease and toxic diseases, and its serological test is positive. (2) Avian influenza H5 and H7 subtypes were seropositive in the poultry in the non-immunized chicken farm. (3) Isolating H5, H7 subtype avian influenza virus strains or other subtype avian influenza virus strains from poultry flocks.
Four, a correct view of highly pathogenic avian influenza
31. How to deal with highly pathogenic avian influenza in a scientific manner?
People have a long history of research on avian influenza, and the first bird flu was discovered in 1878. The world has experienced more than ten pandemics, and the frequency of them has been high in Asia in recent years. The highly pathogenic avian influenza this time is not an infectious disease caused by a new virus. The highly pathogenic avian influenza H5N1 and H7N7 have been reported in other countries and regions in recent years. After years of scientific research, there have been effective methods to control avian influenza. Epidemiological investigation proves that avian influenza is horizontal transmission. Cutting off its transmission route can control the epidemic spread of the disease. The virus is sensitive to high temperature, and it can be inactivated in 2 minutes to 10 minutes at 60 ~ 70℃, so cooked poultry meat, eggs and poultry products can be safely eaten. There’s no need to panic.
32. Is highly pathogenic avian influenza harmful to ordinary citizens?
Under normal circumstances, ordinary citizens are not exposed to sick birds with highly pathogenic avian influenza, because the poultry and poultry products sold in the market have undergone strict inspection and quarantine by the veterinary health department, and sick birds and unqualified poultry products will not enter the market. Therefore, highly pathogenic avian influenza cannot directly pose a threat to ordinary citizens. On the other hand, poultry and poultry products are processed by boiling or barbecue for everyone to eat. In this process, the virus is completely destroyed and inactivated, and it is no longer infectious.
33. What should I do if I have contact with birds with highly pathogenic avian influenza?
First of all, don’t panic, because, after all, the probability of poultry transmitting the disease to people is very low. In the place where the epidemic occurred 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. However, if you have contact with birds with highly pathogenic avian influenza, if you have cold-like symptoms, you should go to the hospital immediately and actively cooperate with doctors for diagnosis and treatment.
V. Rules and regulations related to the prevention and control of highly pathogenic avian influenza
34. How should farmers cooperate with the government to do a good job in areas where highly pathogenic avian influenza occurs?
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. Once the suspected highly pathogenic avian influenza occurs, the suspected sick birds shall be isolated and blocked according to the relevant laws and regulations of animal epidemic prevention in China, and further diagnosed. When it is confirmed to be highly pathogenic avian influenza, the epidemic area should be blocked immediately, the sick birds should be culled and the environment should be thoroughly disinfected in order to prevent the epidemic from spreading further. While the government takes measures, farmers should actively cooperate. Although it will cause certain losses to farmers, it should focus on the overall situation to prevent the spread and spread of the epidemic. At the same time, people’s governments at all levels must put the compensation funds issued by the government into the hands of every farmer.
35. What are the measures announced by the Ministry of Agriculture to prevent and kill highly pathogenic avian influenza?
Strict measures and procedures have been formulated for the prevention, control and eradication of highly pathogenic avian influenza in the "Emergency Regulations on Major Animal Epidemic" and "Emergency Plan for Highly Pathogenic Avian Influenza" formulated by the state. Including: epidemic report, epidemic diagnosis, isolation and blockade of epidemic areas, culling, disinfection, emergency immunization, emergency response system, source and guarantee of funds, etc. Once an epidemic occurs, the state starts the emergency system, and the epidemic will be controlled and eliminated soon.
36. Can farmers handle it by themselves after the outbreak of suspected highly pathogenic avian influenza?
You can’t. The state has clearly stipulated that all poultry and poultry products in epidemic areas must be culled and treated harmlessly under the supervision of 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, environmental disinfection control and epidemic situation confirmation can only be organized and implemented by the local government and the animal husbandry and veterinary administrative department. Farmers slaughter at will, and if blood, waste and polluted water are not treated or improperly treated, it will cause serious environmental pollution and spread of pathogens.
37. What are the conditions to collect diseased materials for pathogen isolation?
Highly pathogenic avian influenza is a kind of infectious disease. In order to prevent the spread of the disease, its pathogen isolation must be carried out in a professional laboratory designated by the Ministry of Agriculture and a laboratory with BSL-3 conditions. Virus isolation and proliferation in laboratories without strict protection conditions is easy to cause virus dispersion and may cause infection of laboratory personnel.
38. How to announce the reported epidemic situation of highly pathogenic avian influenza?
The reported epidemic situation shall be identified by the Ministry of Agriculture and announced in time after pathogen isolation, identification and confirmation by the National Avian Influenza Reference Laboratory designated by the Ministry of Agriculture.
39. What are the responsibilities for violations of discipline and law?
Violations of discipline and law mainly include violation of epidemic reporting and handling system, violation of funds, material guarantee and use system, violation of market management regulations, and disruption of social order. According to the seriousness of the case, the units that violate discipline and law are given disciplinary sanctions such as informed criticism and warning, and the principal responsible persons and other responsible personnel are given disciplinary sanctions such as warning, demotion, dismissal and dismissal according to law. Those who constitute a crime shall be investigated for criminal responsibility.
40. How can farmers in epidemic areas get compensation?
In areas where the epidemic has occurred, the state has implemented economic compensation policies for farmers. It is mainly to compensate the directly culled and verified poultry and the destroyed products in accordance with the relevant policies formulated by the state.
41. Is avian influenza included in the Catalogue of Diseases? Are you sure it is a kind of epidemic disease? Is it included in the compulsory immunization list?
A: Avian influenza has been listed in the list of diseases. The Ministry of Agriculture has listed highly pathogenic avian influenza in the list of first-class animal diseases in China. At present, China has stipulated that emergency compulsory immunization should be carried out for susceptible birds in threatened areas with highly pathogenic avian influenza.