Prevalence and Associated Risk Factors of Avian Influenza H9 in Backyard Poultry Populations of Two Agroecological Zones of Pakistan

Abstract

Avian influenza subtype H9 is epizootic in backyard poultry population of Pakistan. A cross-sectional study was conducted in two districts of Pakistan from two different agro-ecological zones selected as strata to estimate H9 seroprevalence, virus prevalence and to identify risk factors associated with H9 seroprevalence in backyard poultry. A stratified two-stage cluster sampling method was applied to collect samples (n=420) from two strata (agroecological zone). A total of 210 birds were selected as elementary units from 30 clusters (7x30) in each district from each stratum. Blood and oropharyngeal swab samples were collected from each bird. Sera samples were tested by Hemagglutination Inhibition Test (HI) to detect anti-H9 antibodies and swabs samples were tested by RT-PCR for H9. Overall seroprevalence of H9 in two strata was 57.88% (95% CI 34.88-80.87%), while virus prevalence was calculated to be 3.33%. Four factors were identified to be significantly associated (P<0.05) with H9 seroprevalence in the multivariable logistic regression analysis. The odds for H9 seropositivity were 9.43 times higher in flocks with fighting cockerel compared to those having no fighting cockerel (95% CI 4.68 -18.96). Existence of any pond, canal or any other water body near home premises also enhanced likelihood of H9 seroprevalence (OR: 10.04; 95% CI 3.27- 30.83). Backyard chicken raised with other bird species (like ducks, pigeons, or captive wild birds) had higher chances of H9 seropositivity than chicken raised alone (OR 4.12, 95% CI 1.35-12.56). Visit of any farm vehicle to the village had odds ratio of 20.96 (95% CI 5.74-76.51). Future surveillance is recommended to check the level of disease throughout the country