Comparison of outbreaks of H5N1 highly pathogenic avian influenza in wild birds and poultry in Thailand.
Wild bird surveillance for highly pathogenic avian influenza (HPAI) H5N1 virus from 2004 to 2007 in Thailand indicated that the prevalence of infection with avian influenza H5N1 virus in wild birds was low (1.0%, 95% confidence interval [CI]: 0.7-1.2, 60/6,263 pooled samples). However, the annual prevalence varied considerably over this period, with a peak of 2.7% (95% CI: 1.4, 4.1) in 2004. Prevalence dropped to 0.5% (95% CI: 0.3, 0.8]) and 0.6% (95% CI: 0.3, 1.0) in 2005 and 2006, respectively, and then increased to 1.8% (95% CI: 1.0, 2.6) in 2007. During this period, 16 species from 12 families of wild birds tested positive for H5N1 virus infection. All samples from juvenile birds were negative for H5N1 virus, whereas 0.6% (95% CI: 0.4, 0.9) of pooled samples from adult birds were positive. Most positive samples originated from peridomestic resident species. Infected wild bird samples were only found in provinces where poultry outbreaks had occurred. Detection of H5N1 virus infection in wild birds was reported up to 3 yr after eradication of the poultry outbreaks in those provinces. As observed with outbreaks in poultry, the frequencies of H5N1 outbreaks in wild birds were significantly higher in winter. Further understanding of the mechanisms of persistence and ongoing HPAI H5N1 transmission between wild birds and domestic poultry is needed.
Siengsanan
Jarunee
J
The Monitoring and Surveillance Center for Zoonotic Diseases in Wildlife and Exotic Animals, Faculty of Veterinary Science, Mahidol University, Nakhon Pathom, Thailand. hjjar@yahoo.com
Chaichoune
Kridsada
K
Phonaknguen
Rassameepen
R
Sariya
Ladawan
L
Prompiram
Phirom
P
Kocharin
Waraporn
W
Tangsudjai
Sririporn
S
Suwanpukdee
Sarin
S
Wiriyarat
Witthawat
W
Pattanarangsan
Rattapan
R
Robertson
Ian
I
Blacksell
Stuart D
SD
Ratanakorn
Parntep
P
D000818:Animals; D000829:Animals, Domestic / Q000821:virology; D000835:Animals, Wild / Q000821:virology; D001717:Birds; D004196:Disease Outbreaks / Q000662:veterinary*; D004197:Disease Reservoirs / Q000662:veterinary / Q000821:virology; D005260:Female; D053124:Influenza A Virus, H5N1 Subtype; D005585:Influenza in Birds / Q000453:epidemiology* / Q000635:transmission; D008297:Male; D011200:Poultry; D015995:Prevalence; D012367:RNA, Viral / Q000032:analysis; D012621:Seasons; D018571:Sentinel Surveillance / Q000662:veterinary; D013785:Thailand / Q000453:epidemiology
D012367:RNA, Viral