BMC Infectious Diseases. Mapping the risk of avian influenza in wild birds in the US

[tetano]

Mapping the risk of avian influenza in wild birds in the US

Trevon L Fuller email, Sassan S Saatchi email, Emily E Curd email, Erin Toffelmier email, Henri A Thomassen email, Wolfgang Buermann email, David F DeSante email, Mark P Nott email, James F Saracco email, C J Ralph email, John D Alexander email, John P Pollinger email and Thomas B Smith email

BMC Infectious Diseases 2010, 10:187doi:10.1186/1471-2334-10-187
Published: 23 June 2010
Abstract (provisional)

Background

Avian influenza virus (AIV) is an important public health issue because pandemic influenza viruses in people have contained genes from viruses that infect birds. The H5 and H7 AIV subtypes have periodically mutated from low pathogenicity to high pathogenicity form. Analysis of the geographic distribution of AIV can identify areas where reassortment events might occur and how high pathogenicity influenza might travel if it enters wild bird populations in the US. Modelling the number of AIV cases is important because the rate of co-infection with multiple AIV subtypes increases with the number of cases and co-infection is the source of reassortment events that give rise to new strains of influenza, which occurred before the 1968 pandemic. Aquatic birds in the orders Anseriformes and Charadriiformes have been recognized as reservoirs of AIV since the 1970s. However, little is known about influenza prevalence in terrestrial birds in the order Passeriformes. Since passerines share the same habitat as poultry, they may be more effective transmitters of the disease to humans than aquatic birds. We analyze 152 passerine species including the American Robin (Turdus migratorius) and Swainson's Thrush (Catharus ustulatus).
Methods

We formulate a regression model to predict AIV cases throughout the US at the county scale as a function of 12 environmental variables, sampling effort, and proximity to other counties with influenza outbreaks. Our analysis did not distinguish between types of influenza, including low or highly pathogenic forms.

Results

Analysis of 13,046 cloacal samples collected from 225 bird species in 41 US states between 2005 and 2008 indicates that the average prevalence of influenza in passerines is greater than the prevalence in eight other avian orders. Our regression model identifies the Great Plains and the Pacific Northwest as high-risk areas for AIV. Highly significant predictors of AIV include the amount of harvested cropland and the first day of the year when a county is snow free.
Conclusions

Although the prevalence of influenza in waterfowl has long been appreciated, we show that 22 species of song birds and perching birds (order Passeriformes) are influenza reservoirs in the contiguous US.


http://www.biomedcentral.com/1471-2334/10/187/abstract

Open access link to full article (provisional): http://www.biomedcentral.com/content...334-10-187.pdf

[Laidback Al]

Modeled Number of AIV cases in Wilds Birds in the USA (2005-2008). Map extracted from the link to the full article in the post above.

[tetano]

WASHINGTON (Reuters) - Songbirds such as sparrows and thrushes carry various forms of bird flu and could potentially spread the viruses to pigs and poultry, U.S. researchers reported on Tuesday.

The birds carried low-pathogenic avian influenza -- the less dangerous form of bird flu -- but flu viruses can and do swap genes and mutate into more dangerous forms, the researchers said.

A major risk is that the birds would infect pigs, which are suspected "mixing vessels" for new strains of influenza -- notably the ongoing pandemic of H1N1 swine flu, the researchers wrote in the Biomed Central journal BMC Infectious Diseases, available at http://www.biomedcentral.com/1471-2334/10/187/abstract.

...

http://abcnews.go.com/Technology/wireStory?id=11100513