J Infect Dis. Ecologic Risk Factor Investigation of Clusters of Avian Influenza A (H5N1) Virus Infection in Thailand.

[Giuseppe]

J Infect Dis. 2009 May 5. [Epub ahead of print]

Ecologic Risk Factor Investigation of Clusters of Avian Influenza A (H5N1) Virus Infection in Thailand.

Tiensin T, Ahmed SS, Rojanasthien S, Songserm T, Ratanakorn P, Chaichoun K, Kalpravidh W, Wongkasemjit S, Patchimasiri T, Chanachai K, Thanapongtham W, Chotinan S, Stegeman A, Nielen M. - Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands; 2Department of Livestock Development, 3Food and Agriculture Organization, Regional Office for Asia and the Pacific, and 4National Institute of Animal Health, Chatuchak, Bangkok, 5Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai, and 6Faculty of Veterinary Medicine, Kasetsart University, Kampaengsaen, and 7Faculty of Veterinary Science, Mahidol University, Salaya, Nakhon Pathom, Thailand; and 8Department of Medicine and Surgery, Chittagong Veterinary and Animal Sciences University, Chittagong, Bangladesh.


This study was conducted to investigate space and time clusters of highly pathogenic avian influenza A (H5N1) virus infection and to determine risk factors at the subdistrict level in Thailand.
Highly pathogenic avian influenza A (H5N1) was diagnosed in 1890 poultry flocks located in 953 subdistricts during 2004-2007.
The ecologic risk for H5N1 virus infection was assessed on the basis of a spatial-based case-control study involving 824 case subdistricts and 3296 control subdistricts from 6 study periods.
Risk factors investigated in clustered areas of H5N1 included human and animal demographic characteristics, poultry production systems, and wild birds and their habitats.
Six variables remained statistically significant in the final model: flock density of backyard chickens (odds ratio [OR], 0.98), flock density of fighting cocks (OR, 1.02), low and high human density (OR, 0.60), presence of quail flocks (OR, 1.21), free-grazing duck flocks (OR, 2.17), and a poultry slaughterhouse (OR, 1.33).
We observed a strong association between subdistricts with H5N1 virus-infected poultry flocks and evidence of prior and concomitant H5N1 infection in wild birds in the same subdistrict.

PMID: 19416075 [PubMed - as supplied by publisher]
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[Shannon Bennett]

Re: J Infect Dis. Ecologic Risk Factor Investigation of Clusters of Avian Influenza A (H5N1) Virus Infection in Thailand.

I wonder how this data will be received by ornithologists? If you put backyard flocks in an area visited by wild birds the record indicates a statistical rise in H5N1 infections. We would say this is a no-brainer. But, to many out there it will inflame some who are still wedded to the idea that H5N1 infections are due to either poor practices in the poultry industry and/or movement of chickens by poor farmers resulting in the further spread of H5N1.