Abstract
A 1:1 matched case-control study was conducted to identify risk factors for avian influenza subtype H9N2 infection on commercial poultry farms in 16 districts of Punjab, and 1 administrative unit of Pakistan. One hundred and thirty-three laboratory confirmed positive case farms were matched on the date of sample submission with 133 negative control farms. The association between a series of farm-level characteristics and the presence or absence of H9N2 was assessed by univariable analysis. Characteristics associated with H9N2 risk that passed the initial screening were included in a multivariable conditional logistic regression model. Manual and automated approaches were used, which produced similar models. Key risk factors from all approaches included selling of eggs/birds directly to live bird retail stalls, being near case/infected farms, a previous history of infectious bursal disease (IBD) on the farm and having cover on the water storage tanks. The findings of current study are in line with results of many other studies conducted in various countries to identify similar risk factors for AI subtype H9N2 infection. Enhancing protective measures and controlling risks identified in this study could reduce spread of AI subtype H9N2 and other AI viruses between poultry farms in Pakistan.
Highlights
Avian influenza virus (AIV) A subtype H9N2 has become prevalent in domestic poultry in many countries in Asia and The Middle East since the late 1990’s [1]
The analysis presented in this study suggests regardless of the modeling approach that selling birds to live bird retail stalls is strongly associated with an increased risk of AIV H2N9 on the farm
The current study has identified a set of similar risk factors to those identified in other studies from other countries e.g. USA, China, Japan, Hong Kong, Bangladesh, Vietnam, Thailand and Pakistan, which shows that these well-known factors are mainly responsible for increasing risk of AIV infection
Summary
Avian influenza virus (AIV) A subtype H9N2 has become prevalent in domestic poultry in many countries in Asia and The Middle East since the late 1990’s [1]. Outbreaks of AIV subtype H9N2 in commercial chickens have been reported in Iran (1998), Pakistan (1998), China. According to FAO [4] there are four sectors of poultry production systems (i.e Industrial integrated system with high levels of biosecurity; commercial poultry production system with moderate to high biosecurity; commercial poultry production system with low to minimal biosecurity; and village or backyard production system with minimal biosecurity). Pakistan has all four sectors of poultry production system as mentioned above. In Pakistan, poultry production contributes 35% of livestock production and it has become the second largest industry after cotton, with an annual turnover of US$ 2 billion. The poultry sector has proved to be one of the most vibrant segments of the agriculture sector in Pakistan. 1.5 million people are estimated to have benefitted from this sector in terms of employment and income [5]
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