Oct 25, 2006 (CIDRAP News) – Researchers from the University of Georgia report that wood ducks and laughing gulls are highly susceptible to H5N1 avian influenza, which suggests those two species could be sensitive indicators of the virus's presence in wild birds.
In a lab, the researchers exposed six species of wild birds—five duck species and laughing gulls—to the lethal Asian H5N1 virus. All the birds became infected, but only the wood ducks and laughing gulls became ill or died, according to their report in the November issue of Emerging Infectious Diseases.
The findings come amid this year's greatly expanded federal and state program to look for H5N1 avian flu in wild birds in the United States. The deadly Asian strain of H5N1 has not yet been found in North America, but a mild "North American" strain of H5N1 has been found in wild birds in several states.
"If you're looking for highly pathogenic H5N1 in wild birds, it would really pay to investigate any wood duck deaths because they seem to be highly susceptible," David Stallknecht, a study coauthor, commented in a University of Georgia news release.
Besides wood ducks, the ducks used in the study were mallards, Northern pintails, blue-winged teal, and redheads. Those species are the most likely to bring H5N1 to North America, given their behavior and habitat use, lead author Dr. Justin Brown commented in the news release.
The researchers found that the birds studied had more virus in their mouth and throat secretions than in feces. In contrast, said Stallknecht, birds infected with low-pathogenic avian flu viruses shed more virus in their feces, according to the news release.
In other avian flu developments, David Nabarro, the United Nations' senior coordinator for avian and human influenza, said H5N1 is likely to remain a major animal health problem for 5 to 10 more years, according to an Oct 23 UN news release.
"We think it's going to stay that way for five years [or] perhaps 10 years to come because the virus is highly pathogenic yet at the same time can seem to survive in certain communities of birds without symptoms . . . and secondly it does seem to be spread by a combination of wild birds and trade," Nabarro said.
Elsewhere, H5 and N1 avian flu viral proteins were found recently in a green-winged teal in Michigan, but the finding did not signal the lethal Asian type of H5N1, US officials announced Oct 20.
The findings were in one of 51 samples collected from a number of bird species Oct 15 in Tuscola County, Michigan, as part of the expanded wild-bird monitoring program by federal and state agencies. In a news release, the US Department of Agriculture said the finding could indicate two different flu viruses, one containing H5 and the other N1. Another possibility is an infection with the low-pathogenic North American strain of H5N1, which has been found in wild birds elsewhere in Michigan and in Illinois, Maryland, and Pennsylvania in recent months.
Further testing under way at the USDA national lab in Ames, Iowa, will clarify the findings within 2 to 3 weeks, the agency said.
In other recent news about avian flu in birds:
- In an effort to stop avian flu outbreaks, Indonesian officials said they plan to bar people in major cities from keeping free-roaming poultry, according to an Oct 20 Agence France-Presse report. The health minister said the ban could be modeled on similar laws in Thailand and Hong Kong. No date was set for imposing it.
- In China, 42.6 million domestic birds in the Inner Mongolia Autonomous Region have been vaccinated against avian flu since an outbreak last month, the newspaper People's Daily reported Oct 22.
Emerging Infectious Diseases report on wild birds' susceptibility to H5N1
University of Georgia news release about study
UN news release reporting Nabarro's comments