Highly Pathogenic Avian Influenza (HPAI)

hpav

HPAI Q & A


What is Highly Pathogenic Avian Influenza?
The highly pathogenic avian influenza (HPAI) is an avian disease caused by HPAI virus (HPAIV). (See below)HPAI, due to its high lethality and strong propagation, will threaten the stable production and supply of chicken and eggs once the outbreak occurred. Also measures have been taken to prohibit the import of poultry and eggs from Japan to other countries. It will have enormous impact not only on the management of individual farmers but the whole poultry industry. Therefore, it is designated as a domestic animal infectious disease in the Act on Domestic Animal Infectious Disease Control, and the Minister of Agriculture, Forestry and Fisheries prepared and publicly announced guidelines for prevention of the outbreak or spread of HPAI.


What is highly pathogenic? Is it highly pathogenic for humans too?
In the Japan's Act on Domestic Animal Infectious Diseases Control law,, HPAI is stipulated as "a disease of poultry caused by infection with influenza A virus that was judged as highly pathogenic avian influenza virus (HPAIV)" according to the diagnostic criteria prepared by the the World Organisation for Animal Health (OIE). As one of the diagnostic criteria, when 8 chickens were intravenously inoculated with the allantoic fluid of virus-infected embryonated chicken eggs, it causes infections in more than 6 chickens which made them die within a span of 10 days. In other words, "highly pathogenic" is an indicator of the pathogenicity to chickens and not about pathogenicity to humans.


What does H5N1 or H5N8 mean?
Influenza A viruses are divided into subtypes on the basis of two proteins on the surface of the virus: hemagglutinin (HA) and neuraminidase (NA). There are 18 known HA subtypes and 11 known NA subtypes. For example, H5N8 means having H5 subtype of hemagglutinin and N8 subtype of neuraminidase. The highly pathogenic avian influenza virus reported so far are mostly categorized as H5 subtype and H7 subtype.


What symptoms can be seen in chickens with highly pathogenic avian influenza?
In some acute cases, it dies suddenly without showing any symptoms, hence it may be mistaken for E. coli disease, heat stress etc. General symptoms are Loss of energy, decrease in the intake of food and water, decrease in the egg-laying rate, swelling of face, discoloration of combs and legs (purple), cough, runny nose, diarrhea etc.,


How does the highly pathogenic avian influenza spread?
HPAI viruses are highly grown in infected chickens and are excreted in faeces, saliva, sputum and snivel, and can be spread through direct contact of chickens with the secretions. The secreted HPAI contaminate the floor of poultry house or water and induce second contamination of equipment,clothing car, etc. Transmission of HPAI virus from farm to farm is thought to be mediated by the movement of people , equipment and contaminated vehicles.


What is the outbreak of highly pathogenic avian influenza overseas?
Since 2003, the H5N1 subtype highly pathogenic avian influenza virus (HPAIV) spread from Asia, to Europe and Africa. The H5N1 subtype virus is now resident in countries such as China, Vietnam, Indonesia, Bangladesh, India, Egypt and continues to cause highly pathogenic avian influenza (HPAI). Moreover, the Asia type H5N1 subtype virus sporadically causes HPAI in other countries, and the case of HPAI is reported in Cambodia, China, India, North Korea, Laos, Libya, Nepal, Vietnam in 2014. HPAI by H5N2 subtype having the same genetic origin as the hemagglutinin (HA) gene of the Asian type H5N1 subtype HPAIV occurred in China in December 2013. Similarly HPAI by the H5N8 subtype occurred in Korea in January 2014and 12 million poultry (mainly ducks) in 472 farms was culled.
In 2011, H5N2 subtype HPAIV with different HA genes from Asian type H5 virus was reported in South Africa. In 2012, the same type virus cause HPAI in Taiwan leading culling of 40,000 poultry . Also,regarding HPAIV of the H7 subtype, the H7N7 subtype was reported in Australia in 2012, H7N3 subtype was reported in Mexico. In 2013 the H7N2 subtype was reported in Australia, H7N7 subtype in Italy.
The occurrence of HPAI by H5N6 subtype virus has been reported after 2014 in China, Vietnam, Laos.


What is the past outbreak of highly pathogenic avian influenza in Japan?
In Japan, highly pathogenic avian influenza (HPAI) by H5N1 subtype virus occurred in 2004, 2007, 2010-2011. In the occurrence in 2004, approximately 275,000 chickens in 4 farms at 3 prefectures were culled. In the occurrence in 2007, 170,000chickens in 4 farms at 2 prefectures were culled. In the outbreak of 2010-2011, 1.85 million chickens at the 24 farms in 9 prefectures, the largest number ever, were culled. In the period of 2010-2011, H5N1 subtypeHPAI virus was isolated from 60 dead birds in 16 prefectures. In April 2014, for the first time in Japan, HPAI caused by H5N8 subtype virus occurred, and 110 thousand chickens were slaughtered for protection. Thereafter, from December 2014 to January 2015, HPAI by H5N8 subtype virus occurred on 5 farms and 350 thousand chickens were culled.
According to the genetic analysis of the viruses that caused HPAI in Japan in the past so far, the viruses involved in each occurrence can be clearly distinguished genetically. It suggests that each virus came from overseas independently and not derived from one which exist persistently in Japan.


What measures should be taken when suspected poultry with highly pathogenic avian influenza is found?
When infection of highly pathogenic influenza is suspected, for example the number of birds died in the breeding poultry is observed to be increased by more than twice than the usual condition, then it should be reported immediately to the nearest animal health department.


How can we prevent farms from highly pathogenic avian influenza?
It is highly essential that the spread of highly pathogenic avian influenza virus (HPAIV) via wild birds, wild animals, people, things into the poultry house should be prevented by carrying out thorough the general Rearing Hygiene Management. The Ministry of Agriculture, Forestry and Fisheries (MAFF) has prescribed hygiene management guidelines and Standards of Rearing Hygiene Management for poultry. In accordance with these standards, prefectures make an effort to check the farm regularly to improve the awareness of the prevention of farmers, regular health observation, thorough setting of hygiene control areas and disinfection, also they are trying to prevent intrusion of wild birds into poultry houses by means of bird net. The Ministry of Environment examines the feces of dead birds and wild birds and strive to discover the HPAIV that entered the country as soon as possible.


How is the highly pathogenic avian influenza diagnosed?
In prefectures, veterinarians collect swab samples from chickens and detect type A influenza virus using commercially available immunochromatographic kit. Subtype of hemagglutinin is determined by PCR method using RNA from swab samples. Swab samples were inoculated into embryonated chicken eggs to isolate influenza A virus.
In the Division of transboundary animal disease, National Institute of Animal Health, NARO, we will determine subtypes of hemagglutinin and neuraminidase of viruses sent from prefectures. Also, by sequencing of the hemagglutinin gene, we check the presence of amino acid sequence which is typical of highly pathogenic avian influenza virus. In addition, we test the pathogenicity of the virus by intravenously inoculation of the isolated virus into chickens.


What kind of measures has been taken when poultry is diagnosed as highly pathogenic avian influenza (HPAI)?
All poultry in the farm has to be quickly culled. Dead bodies should be buried or incinerated. All items in the farm has to be incinerated or sterilized and Poultry house also has to be sterilized.
In principle, movement of poultry or objects that are likely to spread HPAI virus should be forbidden for areas within 3 kilometers of radius (Movement restricted area). For areas within a radius of 10 kilometers, movement of living poultry etc within the area or from outside to that area is permitted, but outward movement is prohibited (Carry-out Restricted area). These movement - restricted areas, after checking the epidemic prevention measures and once confirmation of cleaning inspection is done, the restrictions can be canceled.


Does highly pathogenic avian influenza infect humans?
Generally, the highly pathogenic avian influenza virus (HPAIV) does not infect humans. However, it is known that if you are in direct contact with poultry that excrete HPAIV and are exposed to a large number of viruses, there may be slight possibility for infection. In other countries where highly pathogenic avian influenza (HPAI) is prevalent, since 2003, 856 people were found to be infected by the H5N1 subtype virus till October 2016, among them 452 people have died. 13 people were found to be infected by the H5N6 subtype virus since 2014, among them 5 have died.


Do we have possibility of infection by eating chicken or eggs?
Chicken meat and eggs contaminated with highly pathogenic avian influenza virus do not distribute in the market in Japan. Also the viruses are easily inactivated by cooking and gastric acid. Hence there is no possibility of infection by eating chicken or chicken eggs.


Press Release

Genetic characteristics of Highly pathogenic avian influenza (HPAI)

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