The Yomiuri Shimbun
(Apr. 7, 2009)

UTSUNOMIYA–Ten wild raccoons have been found with signs of previous H5N1 bird flu infections, according to a joint study by Tokyo University and Yamaguchi University.

This is the first time mammals in this country have been found with bird flu virus antibodies, which develop as a result of infection. Before the discovery, only birds had been found with bird flu antibodies.

The research team, which presented a paper on its findings at a conference of the Japanese Society of Veterinary Science in Utsunomiya on Saturday, warned that infected raccoons could introduce the virus into chicken farms and noted that countermeasures were needed.

It is believed that the H5N1 strain of the bird flu virus is highly likely to mutate into a new type of influenza. In Japan, there have previously been reports of domestic chickens, wild whooper swans, jungle crows and mountain hawk-eagles infected with the virus.

The research team collected and examined blood from 988 raccoons captured since 2005 at three locations in western Japan and one location in eastern Japan. In the blood of 10 raccoons from three of the locations, the team found antibodies that had developed after past H5N1 infections. In two of the three places, not even birds had been found with the antibodies before this time.

According to Taisuke Horimoto, an associate professor of Tokyo University’s Institute of Medical Science, raccoons do not live in packs. He said the blood test this time showed that in comparison with other infectious diseases, the proportion of animals found with the H5N1 antibodies was low.

The researchers think the 10 raccoons likely were not infected by other raccoons, but by eating the carcasses of infected birds or inheriting the antibodies from a parent at birth.

Raccoons are found throughout the nation. Many of them are descended abandoned pets or have run away from zoos.