Avian influenza is the abbreviation of avian influenza, which 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, with low mortality; Or more serious systemic, hemorrhagic and septic symptoms, and the mortality rate is 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. Diseases caused by H5 and H7 subtype strains (represented by H5N 1 and H7N7) are called highly pathogenic avian influenza (HPAI). Recently, avian influenza caused by H5N 1 subtype at home and abroad is highly pathogenic, with high morbidity and mortality and great harm. 2. What is the pathogen of highly pathogenic avian influenza?
Influenza viruses can be divided into three types: A, B and C, and avian influenza virus belongs to type A influenza virus. Influenza A not only infects people, but also infects other animals, while influenza B and C mainly infect people. The genome consists of eight fragments of different sizes. The variation of influenza virus is mainly caused by the point mutation of one or several gene fragments in its genome or the recombination of genome fragments between different influenza viruses.
According to the antigenicity difference between hemagglutinin (HA) and neuraminidase (NA), influenza virus can be divided into different serum subtypes. Up to now, influenza A virus 15 HA subtype, namely H1-H15, has been found. Nine subtypes of NA have been found, namely N 1-N9. HA and NA subtypes identified at present can be separated from poultry.
The highly pathogenic avian influenza found at present is caused by H5 or H7 subtype avian influenza virus, but not all H5 or H7 subtype avian influenza viruses can cause highly pathogenic avian influenza.
Avian influenza virus has low resistance, and common disinfectants are easy to inactivate. It is also sensitive to heat, and loses its activity when heated at 56℃ for 30 minutes and 100℃ for 5 minutes. It's getting hotter and hotter. What is the trend of bird flu?
Influenza A likes cold and humid places, so its frequent seasons are in winter and spring, usually in 1 month and February. Summer is rare. Therefore, hot weather will greatly reduce the prevalence of avian influenza. 4. What do H and N of avian influenza virus mean?
H and n both refer to viral glycoproteins. One glycoprotein is called hemagglutinin (HA) and the other is called neuraminidase (NA). Because these two glycoproteins are prone to mutation, HA can be divided into fifteen different types (H 1 ~ H 15) and NA can be divided into nine different types (N 1 ~ N9) according to the variation of glycoproteins. 5. Preventive measures for highly pathogenic avian influenza?
(1) Strengthen the quarantine of customs and domestic circulation to prevent the introduction and spread of avian influenza.
1. The national customs strictly quarantine imported poultry to prevent the introduction of highly pathogenic influenza virus (HPAI) from abroad.
2, domestic veterinary quarantine departments should do a good job in poultry circulation field (such as markets, slaughterhouses, traffic arteries) quarantine and monitoring, at the same time, domestic poultry farms should regularly carry out serological monitoring. Combine these two aspects to understand the epidemic dynamics of avian influenza in China and prevent the spread of the epidemic.
(two) strictly implement and improve the biological safety measures of poultry farms.
1. Avoid contact between poultry and waterfowl such as geese, ducks or wild birds.
2. The chicken farm should be located far away from rivers and lakes where waterfowl and wild birds inhabit;
3, poultry farm staff don't keep birds, dogs and cats.
4. Adopt closed feeding to prevent wild birds from entering the poultry house through doors and windows;
5. Prevent water or feed from being polluted by wild bird droppings;
6. Set disinfection facilities in the production area of poultry farm to thoroughly clean and disinfect the vehicles entering and leaving;
7. Feeding personnel should change clothes, hats, shoes and boots and take a bath when entering the production area;
8, strictly put an end to other poultry farm personnel to visit;
9, regular disinfection of birds, poultry houses and the surrounding environment.
10, regularly eliminate mosquitoes, flies, rodents and other harmful insects in poultry farms;
1 1. Dead birds must be burned or buried deeply;
12, poultry farms adhere to the breeding mode of self-propagation, self-support, all-in and all-out, and when introducing poultry varieties and their products, they must come from poultry farms without bird flu;
13, do a good job in poultry feeding management and improve the disease resistance of poultry; Minimize the occurrence of stress factors; Pay attention to the climate change in autumn and winter, winter and spring, and do a good job in keeping warm and cold. 6. When did the bird flu happen?
1878, a large number of chickens died in Italy, which was called chicken plague at that time. By 1955, scientists confirmed that its pathogenic virus was influenza A virus, and the disease was renamed avian influenza. Subsequently, the disease also occurred locally in other European countries, South America and Southeast Asia, the United States and the Soviet Union, and now it has spread almost all over the world. Especially since the end of 1990s, the outbreaks of avian influenza in Eurasia have become more and more frequent.
1In May 1997, the first case of avian influenza occurred in a chicken farm in Hongkong, China. Experts have determined that A/H5N 1 Avian influenza virus is the chief culprit of a large number of poultry deaths in the Hong Kong Special Administrative Region. However, this virus, which has always threatened the lives of poultry, has a new mutation, which can spread to mammals and even humans. 1In August 1997, a 3-year-old boy died of bird flu. This is the first case of human infection with A/H5N 1 in the world. In the following months, * * * 18 people were infected with avian influenza virus, and 6 of them died. In order to prevent the A/H5N 1 avian influenza virus from further spreading to human beings, the Hong Kong SAR Government slaughtered1300,000 poultry. This is considered to be the most serious bird flu epidemic in the world at present.
On March 1 day, 2003, H7N9 avian influenza virus was found in six farms in the eastern Netherlands near the German border. By March 3, the number of farms with bird flu epidemic has risen to 13. On the same day, in order to prevent the epidemic from spreading to other European countries, the EU announced a total ban on the export of Dutch live poultry and their eggs. Bird flu has dealt a heavy blow to the Netherlands, one of the largest poultry exporters in the world. What's more, 80 people were infected with avian influenza virus during the epidemic, among which a 57-year-old Dutch veterinarian was infected with the virus while testing sick chickens and died of pneumonia complications caused by avian influenza. Subsequently, H7N9 avian influenza spread throughout Europe, and cases of avian influenza virus infection also appeared in Belgium and Germany adjacent to the Netherlands. This is by far the most widespread spread of avian influenza in the world. 7. Is bird flu really more terrible than SARS?
Under normal circumstances, avian influenza virus will not make people sick. The World Health Organization thinks that bird flu may be more threatening than SARS because of two factors. First, once the bird flu mutates, it may become an ordinary human influenza virus, and the human body has almost no immunity to the new influenza virus. Secondly, human influenza virus is far more contagious than SARS virus. Influenza virus can spread rapidly in the air, while SARS virus usually spreads only after close contact, so once avian influenza mutates into ordinary human influenza, its spread speed will greatly exceed that of SARS. 8. How long is the incubation period of highly pathogenic avian influenza? Is the incubation period contagious?
The incubation period of avian influenza varies from several hours to several days, and the longest incubation period can reach 2 1 day. The incubation period is affected 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 in the incubation period. 9. What is the transmission route of avian influenza?
There are two modes 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 and management appliances, transport vehicles, insects and various birds carrying viruses, can be spread mechanically. Healthy birds can be infected through respiratory tract and digestive tract, causing diseases. 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 can cause bird infection and illness through polluted environment (such as water source). The circulation of poultry flocks and poultry products with avian influenza virus will cause the spread of avian influenza. 10. What are the main clinical manifestations of highly pathogenic avian influenza? What's the difference with Newcastle disease?
Highly pathogenic avian influenza has no specific clinical symptoms, which are characterized by sudden onset, loss of appetite, sudden rise in body temperature, high mental depression, edema and cyanosis of cockscomb 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. The 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 develop typical Newcastle disease, and infected chickens generally show mild respiratory symptoms, nervous system symptoms and decreased egg production of laying hens, with low mortality. 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 of different ages can be infected with highly pathogenic avian influenza, which has an urgent onset and rapid spread, and the mortality rate can reach 100%. 12. Is the occurrence of highly pathogenic avian influenza related to the age, sex and species of poultry?
Chickens, turkeys, guinea fowl, quails, ducks and geese can be infected, but chickens, turkeys, ducks and geese are more common, among which turkeys and chickens are the most susceptible, with higher morbidity and mortality. Waterbirds such as ducks and geese have low susceptibility, but they can be infected with viruses or recessive infections, sometimes causing a large number of deaths. All kinds of chickens and turkeys of different ages can be infected and die, but the mortality rate of waterfowl such as ducklings and goslings is high. It has not been found that the occurrence of highly pathogenic avian influenza is related to the sex of poultry. 13. Will highly pathogenic avian influenza spread through eggs?
The spread of highly pathogenic avian influenza among birds mainly depends on horizontal transmission, such as air, feces, feed and drinking water. Current evidence shows that highly pathogenic avian influenza will not spread through eggs. However, experiments show that the eggs infected with chickens contain influenza virus, so the possibility of vertical transmission cannot be completely ruled out. The fertilization rate and hatching rate of infected chickens decreased, so they could not be used for hatching. 14. Why does 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 high 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 henhouse environment, so 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. 15. Is there a vaccine to prevent highly pathogenic avian influenza?
China has successfully developed a vaccine to prevent H5N 1 highly pathogenic avian influenza. Farms in non-epidemic areas should be vaccinated in time to prevent the occurrence of bird flu. 16. 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, 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. This can put out the epidemic as soon as possible, eliminate the source of infection and reduce economic losses. This is one of the effective means to fight bird flu and should be resolutely implemented. 17. How should poultry houses, pollutants and their environment be disinfected?
Influenza virus can pollute poultry houses, cages, padding and so on with the excretion of feces and nasal secretions from infected birds. Influenza viruses are sensitive to disinfectants and heat. When the contaminated 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 with flame. Due to the high virus content in feces, special attention should be paid to the treatment. Feces and bedding should be buried, and the tools used for treatment should be soaked in caustic soda water or other disinfectants for disinfection. 18. which disinfectants can effectively kill avian influenza virus? How to use it?
Avian influenza virus has poor viability 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 viruses in the environment. The following disinfectants have good disinfection effect in the field environment:
(1) Formaldehyde disinfectants include formaldehyde and paraformaldehyde, among which formaldehyde fumigation is the most commonly used. 7 ~ 2 1 g potassium permanganate per cubic meter, adding 14 ~ 42 ml formalin, can fumigate and disinfect closed pens. When fumigating and disinfecting, the room temperature is generally not lower than 65438 05℃ and the relative humidity is 60%~80%. Potassium permanganate can be added to the container first, then formalin solution can be added, and the doors and windows can be sealed for more than 7 hours to achieve the purpose of disinfection, and then the doors and windows can be opened for ventilation to eliminate residual odor.
⑵ The disinfection effect of chlorine-containing disinfectant 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 disinfection is rapid, no residue, no odor, and is often used for disinfection of equipment and countertops in food factories and slaughterhouses.
⑶ Alkaline preparations mainly include sodium hydroxide, etc. Sodium hydroxide preparations used for disinfection are mostly crude lye containing 94% sodium hydroxide, which is often heated to prepare 1%~2% aqueous solution, which is used for disinfection of chicken coops, walls, sports fields and dirt contaminated by viruses, as well as for disinfection of slaughterhouses, food factories and other ground and transport vehicles. After spraying for 6~ 12 hours, rinse with clear water. 19. Will the mixed culture of chickens, ducks, geese and pigs lead to the occurrence of highly pathogenic avian influenza?
Poultry should not be mixed with pigs, because poultry influenza virus can infect pigs, and human influenza virus can also infect pigs. Because influenza virus has eight different nucleic acid fragments, when these two different virus particles infect a cell, their nucleic acid fragments will be rearranged 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 do not show any clinical symptoms. After the virus in their feces infects chickens, it can cause the occurrence and prevalence of avian influenza and cause serious economic losses. 20. Is it useful to strengthen the management of poultry breeding to prevent avian influenza?
Strengthening feeding management is the premise of preventing 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 isolating farms and pens, disinfecting the environment, controlling the flow of people and articles, etc., to prevent birds from being harmed by other diseases. 2 1. How to prevent highly pathogenic avian influenza?
Comprehensive preventive measures must be taken to prevent bird flu. 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 surrounding environment, incubation halls, incubators, chicken coops, clothes and shoes of staff. Adopt all-in and all-out feeding methods to prevent contact between birds and birds; The farm should have a special passage for the staff to enter and exit, and the staff and their daily protective equipment 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 the reliable immune prevention effect of the vaccine. 22. How can hatcheries and hatcheries prevent highly pathogenic avian influenza?
First of all, the design of incubator should be done well. It should be a one-way traffic route from the egg feeding room, egg loading room, hatching room, waiting room, 1 day-old chick loading workshop to the loading area of the transport vehicle. Each incubator must be conducive to thorough cleaning and disinfection, and the ventilation system should be able to prevent the recirculation of polluted air and dust.
The second is to do a good job in the inspection and timely disinfection of eggs. Breeders should collect eggs regularly after laying eggs, remove dirt on the surface in time, and eliminate eggs that are seriously polluted and cracked.
Third, do a good job in cleaning and disinfecting incubators, egg trays, eggs and incubators before hatching.
Fourth, thoroughly disinfect the vehicles and equipment transporting young birds to prevent cross-infection.
Fifth, under the guidance of the local veterinary health management department, breeders are immunized, and chicks are also immunized. 23. Is there a relationship between 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, causing them to get sick.
Grazing or stocking poultry are more likely to come into contact with other poultry, migratory birds or the environment, feed and drinking water polluted by these wild animals, and the probability of contracting avian influenza is greatly increased.
Intensive poultry is less likely to be infected with avian influenza because of good environmental isolation conditions, strict personnel and logistics control, and good veterinary health and epidemic prevention measures, and once it happens, control measures can be taken quickly. 24. What is the recommended immunization program for highly pathogenic avian influenza?
In the event of an epidemic, susceptible birds within 5 kilometers around the epidemic area must be vaccinated urgently, and an immune isolation belt should be established around the epidemic area. Vaccination is only used for healthy chickens that are not infected with highly pathogenic avian influenza virus. Breeding chickens and commercial laying hens should generally be vaccinated 2~3 times. Emergency immunization must be carried out under the guidance of veterinary personnel. 25. 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%. 26. Why should poultry within a radius of 3 kilometers around the highly pathogenic avian influenza epidemic be culled?
In China, highly pathogenic avian influenza is classified as an epidemic area within a radius of 3 kilometers around the epidemic spot, because poultry within a radius of 3 kilometers 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 extinguished, it is absolutely necessary to cull all the poultry around the epidemic spot and within 3 kilometers. This will help to control the spread of pathogens caused by sick birds and their droppings, sewage and other pollution sources. This is the most effective way to control serious infectious diseases, and it is also an international practice. 27. Why should culled poultry be treated harmlessly?
Because culled poultry may contain highly pathogenic avian influenza virus, if these pathogens are not eradicated, allowing sick poultry to flow into the market 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 epidemics, culled poultry must be burned and buried harmlessly. 28. Why should the highly pathogenic avian influenza epidemic area be blocked?
Isolate and block highly pathogenic avian influenza epidemic areas as soon as possible, restrict the movement of poultry, personnel and means of transport, prevent highly pathogenic influenza virus from spreading from epidemic areas to non-epidemic areas, prevent the epidemic from further expanding, and reduce the major economic losses and international impact caused by highly pathogenic avian influenza. 29. When highly pathogenic avian influenza occurs, why should the focus be tracked?
Because timely and thorough elimination of the epidemic source is the key to control highly pathogenic avian influenza. When highly pathogenic avian influenza occurs, it is necessary to report the epidemic situation in time, find the epidemic spot as soon as possible, block the epidemic spot and cull poultry in a short time, which can effectively prevent the spread and spread of avian influenza epidemic. 30. What is the time limit for lifting the blockade?
The longest incubation period of avian influenza is 2 1 day, during which new cases of avian influenza virus infection may occur at any time. 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 blockade area. After the blockade is lifted, it can be guaranteed that there will be no new highly pathogenic influenza epidemic in this area, thus achieving the purpose of putting out the epidemic. Therefore, the blockade of highly pathogenic avian influenza epidemic areas can only be lifted after the last poultry is culled for at least one incubation period.