KUMAMOTO - Restrictions on poultry shipments put in place due to an outbreak of highly virulent avian influenza in Taragi, Kumamoto Prefecture, have been lifted because recent tests for the virus have all been negative, the prefectural government said Thursday.
Infection-control operations based on lessons learned in past outbreaks of foot-and-mouth disease and bird flu are seen as having helped prevent the virus from spreading to other farms.
The prefecture has been conducting infection testing at two other poultry farms in the movement-restricted area designated on April 27 within a three-kilometer radius around the poultry farm where the outbreak occurred. Visual examinations of about 37,000 birds revealed no abnormalities. The prefecture announced that serum-antibody tests and virus-isolation tests performed on blood and other samples from chickens in the restricted-movement area have revealed no new infections.
Though the prefecture lifted a general ban on outside shipments from areas three to 10 kilometers from the farm where the outbreak occurred, restrictions on the movement of chickens and eggs inside the restricted area will remain, likely until May 8.
"I felt I had to report it quickly, so what happened before wouldn't repeat itself," the manager of the poultry farm where the outbreak occurred told The Yomiuri Shimbun in a telephone interview.
The man was referring to massive outbreaks of bird flu that occurred in 2010 and 2011. Infections in neighbouring Miyazaki Prefecture were not controlled, and 1.02 million birds at 13 farms had to be slaughtered.
On April 11, the man discovered several dozen dead birds in one of his chicken coops. After more than 100 birds died the next day, he suspected an outbreak.
He called a veterinarian, who performed simple testing. The results were positive, and he quickly contacted the Kumamoto prefectural government.
If no new infections occur, even the farm where the outbreak occurred could be reopened soon.
"I still think, 'Why me? Why now?' but I'm glad it didn't spread to other [farms]," the man said.
Highly virulent avian influenza, such as H5 subtypes, infects poultry and can cause large numbers of deaths.
Infection of humans, while rare, can occur if birds' internal organs are handled or large amounts of fecal dust are inhaled. Human infections have been reported in China and countries in Southeast Asia.
Infected meat is not dangerous if fully heated to at least 70 C.
The harsh experiences of the past helped prevent a wider infection.
Mistaken decisions and delays in reporting in a foot-and-mouth disease outbreak in Miyazaki Prefecture in 2010 led to the slaughter of 300,000 cows, pigs and other animals.
Slow reporting was also seen in a bird flu outbreak in Kyoto in 2004.
The government revised the Domestic Animal Infectious Diseases Control Law in 2011 in response to these incidents.
The revision established a system that bars farmers who are overly slow in reporting suspected infections from receiving compensation for slaughtered animals. It also set guidelines for slaughter and burial times.
The prefecture confirmed the positive result in simple testing on the night of April 12. Without waiting for the results of genetic tests, preparations for slaughter and other measures were begun.
Prefectural officials were dispatched before dawn, and from the time genetic testing finished to the last slaughtered animals were buried took 71 hours 30 minutes, just within the 72 hours set in the guidelines. The lessons learned in Miyazaki Prefecture and other places had proven their worth.
"Kumamoto Prefecture was able to work off of prior hypotheses, which helped make the initial actions appropriate. This will be a model for the whole country," said Koichi Otsuki, a veterinary microbiologist and head of an avian influenza research centre at Kyoto Sangyo University.
A high-ranking official of the Agriculture, Forestry and Fisheries Ministry praised the response to the outbreak, saying it was due to "the accumulation of difficult experiences," and suggested that information should be shared among the prefectures.
Although the outbreak was successfully contained, issues remain regarding how to prevent initial infections. Avian influenza enters Japan via migratory and other wild birds, and finds its way into chicken coops on small birds, mice, people's shoes and other vectors.
At the poultry farm where the outbreak occurred, nets to keep wild birds out were found to be slack, and there were gaps in walls large enough for mice and other animals to pass through.
Still, "the hygienic conditions at the farm were normal. It's difficult to keep things perfect at all times," a farm ministry official said.
"It would be ideal if infected wild birds that had died could be found, which would suggest the virus has made it into the country. Then, poultry farms could be inspected to prevent the virus from getting in," said Toshihiro Ito, a professor of public health at Tottori University.