Study links waterfowl preening to avian flu transmission

Jun 28, 2010 (CIDRAP News) – Researchers have found that preening activities in birds can contribute to avian influenza transmission, which could change the way animal health experts conduct surveillance and fight the virus.

The findings, published in Public Library of Science (PLoS) One, suggest preen oil glands secretions, which waterproof the feather of aquatic birds, support a mechanism that concentrates avian flu viruses from water onto birds' bodies. The investigators are from three Italian veterinary research centers and St Jude Children's Research Hospital in Memphis, Tenn.

In looking for a common denominator among waterfowl that could attract avian influenza viruses from water, the group hypothesized that preen oil might be a natural capture system that progressively concentrates the viruses on the birds' bodies.

To test the possibility, they took feather and cloacal swabs of wild mallards in Italy's Tuscany region between Dec 2006 and Aug 2007. They then performed lab experiments to test the interaction between waterborne avian influenza viruses and preen oil in both freshwater and saltwater.

They found that feather swabs were 2.5 time more likely to show evidence of avian flu viruses than cloacal swabs (27% versus 11%).

In the second part of the experiment, they found no avian flu viruses in duck uropygial glands, the organ that produces the preen oil. The group concluded that the absence suggests the flu viruses originated externally, which they say supports their suspicion that preened feathers are an ecologic link between waterfowl and the environmental persistence of avian flu viruses.

Because both infected and noninfected ducks can carry the virus on their feathers, routine surveillance—which typically involves cloacal and tracheal sampling for the virus—may produce false-negatives, meaning new detection methods may be needed to detect avian influenza on the birds' bodies.

They said H5N1 avian influenza infections have been reported in people who have defeathered dead swans and that the feather-flu connection might partially explain why women, because they are more often involved in defeathering activities, have a higher incidence of H5N1 infection.

The group wrote that more studies are needed to explore how the proposed preening-mediated infection mechanism is affected by other variables such as long-distance movements and long-term infectivity of avian flu viruses.

In other avian flu developments, Vietnam's agriculture ministry today confirmed an H5N1 outbreak at a farm in Thai Nguyen province in the northern part of the country, Xinhua, China's state news agency, reported. Local officials culled 500 ducks with suspected infections, have disinfected the affected area, and have controlled poultry movements to control the spread of the virus.

Elsewhere, veterinary officials in Russia reported finding the H5N1 virus in wild birds found dead on a lake in Tyva republic in southern Siberia, according to a Jun 25 report to the World Organization for Animal Health (OIE). The location is Ubsu Nur, a lake at the border between Tyva and Mongolia. The report said 367 birds were affected but didn't specify the species.

See also:

Jun 25 PLoS One study

Jun 25 University of Bologna press release

Jun 28 Xinhua story

Jun 25 OIE report

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