Since last month, bird flu has been occurring one after another at an unusual pace in various parts of Japan, but Kagoshima University investigated and found that a virus of a different strain from that found in various parts of the country was found.
The research group says that strict caution is required, saying that wild birds carrying multiple strains of virus from multiple routes to various places may lead to the spread of infection.
The virus detected in Japan this season has almost the same gene as the highly lethal and highly pathogenic avian influenza virus "H5N8" that was prevalent in Europe last season, and migratory birds pass through Siberia, the nesting site, to Japan. It is believed that it was brought to.
On the other hand, when a group at Kagoshima University collected and analyzed the water in the rice fields where migratory birds flew in Kagoshima Prefecture on the 21st of this month, another strain of virus was detected.
Although the virus is the same "H5N8 type" that has been found so far, the gene sequence is very different and is in close agreement with the virus that has spread in Europe this season.
In addition, this virus has many confirmed deaths of wild birds, and the mortality rate may be slightly higher even in chickens.
The research group says that wild birds carrying multiple strains of virus from multiple routes to various locations may lead to the spread of the infection.
Associate Professor Makoto Ozawa of Kagoshima University said, "It is thought that a large amount of virus is invading Japan through various routes. It seems that the environment is being polluted by the virus, so strict caution is required." ..
The characteristic of this season's virus is "hard to notice infection"
It is believed that the background to the unusual pace of bird flu outbreaks this season is the spread of infections overseas, such as Europe, and the characteristics of viruses that are difficult to notice.
In Europe, it became popular in Eastern Europe such as Poland and Hungary last season, and once it was settled, but after October, it expanded to a wide range such as Germany, the Netherlands, the United Kingdom and Denmark, and on the 23rd of this month. At that time, viruses have been detected in chicken farms and wild birds in 15 countries.
It has also been detected in Japan and South Korea in Asia, as well as in Iran and Israel in the Middle East.
From the analysis results of the virus genes detected in Japan since last month, it seems that the virus spread in Europe was carried to Siberia, the nesting site, by migratory birds and brought to Japan. A research group at the university says that it may have been brought to various places from Siberia, the nesting site of migratory birds, to Hokkaido via Sakhalin and the Kuril Islands, or by multiple routes via the Korean Peninsula.
In addition, the virus detected this season has a longer time to die than previous viruses even if infected, and it is thought that the fact that the infection is less noticeable also affects the spread.
A national research institute, Agricultural and Food Industry Technology Research Organization, conducted an experiment to infect chickens with a highly pathogenic "H5N8 type" virus detected at a poultry farm in Mitoyo City, Kagawa Prefecture. It took up to 6 days to die even if infected with the virus.
The virus detected in Yamaguchi Prefecture in 2004 and the virus detected in Otoshi Kagawa Prefecture all died by the third day, so this virus is characterized by a long period from infection to death. about it.
In addition, even if infected, there are no symptoms such as purple color of the comb, and a large number of chickens do not die immediately, so the infection may spread in the poultry farm without noticing it.
The Ministry of Agriculture, Forestry and Fisheries says that it is necessary to take strict precautions, such as observing chickens on a daily basis and notifying them early if they have unusual symptoms such as lack of energy and eating less food.
Poultry farms that do not comply with hygiene management standards
Since last month, bird flu has been occurring one after another in various parts of western Japan such as Kagawa and Miyazaki prefectures, but it was confirmed in Chiba prefecture on the 24th of this month, and the range is expanding.
The first outbreak of bird influenza was confirmed in Kagawa prefecture this season, then in Shikoku, Kochi prefecture, Tokushima prefecture, in Kyushu, Fukuoka prefecture, Miyazaki prefecture, Oita prefecture, and in the Chinese region, Hiroshima prefecture and Okayama prefecture. In Kansai, it occurs in 32 chicken farms in Hyogo, Nara, Wakayama, Shiga, and in Kanto, 13 prefectures in total, and the number of chickens killed is expected to reach more than 4.6 million. is.
In just about two months, infections have been confirmed one after another, making it an unprecedented event.
In previous field surveys by a team of national experts, there are poultry and rivers around each poultry farm for wild birds carrying the virus, as well as gaps for wild animals to enter the poultry farm, and people and vehicles. There are many poultry farms that do not fully comply with national hygiene management standards, such as insufficient disinfection of poultry farms, and viruses carried around the poultry farms by wild birds are brought in through wild animals, people and vehicles. It has been pointed out that it may have been done.
In addition, viruses have been detected in eight prefectures such as Hokkaido, Kagoshima, and Niigata prefectures from the carcasses and feces of wild birds, and the Ministry of Agriculture, Forestry and Fisheries has said that the risk of outbreaks nationwide is extremely high, and is calling for increased vigilance. I will.
Expert "Viruses everywhere in Japan"
Professor Yoshihiro Sakoda of Hokkaido University, who is familiar with bird flu, said that bird flu is occurring at an unusual pace this season, saying, "Migratory birds have brought the virus to Japan by multiple routes, and it is in a situation where it is everywhere in the country. I think that is the biggest factor. Even if there are many viruses in the environment, it can be prevented if hygiene measures are taken at the chicken farm, but since there has been no outbreak of bird flu in the last few seasons, chicken raising It is undeniable that there was some slack in the measures taken at the venue. "
In addition, regarding the long period from infection of chickens to death, "Because it takes a long time to shed the virus, it also becomes a factor to spread the virus to the surroundings, and it is delayed to find abnormalities. As a countermeasure, we will conduct close daily observations, and if the mortality rate increases, we will promptly notify the relevant organizations. "
Regarding the outlook for the future, "The current situation is very pessimistic before January and February, when the infection is still easy to spread. I think there is no doubt that the amount of virus in the environment is higher than ever. Hygiene measures In March and April to minimize outbreaks in poultry farms, all parties must work together until the end of the season when migratory birds fly in. For the poultry industry , The biggest crisis ever, ”he emphasized the need to strengthen countermeasures.