title: A case-control study to identify risk factors associated with avian influenza subtype H9N2 on commercial poultry farms in Pakistan.
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.
authors.affiliation: Division of Infection and Pathway Medicine, The University of Edinburgh Medical School, Edinburgh, Scotland, United Kingdom.
authors.forename: Mamoona
authors.initials: M
authors.lastname: Chaudhry
authors.affiliation: Department of Clinical Medicine and Surgery, University of Veterinary and Animal Sciences, Abdul Qadir Jilani Road, Lahore, Pakistan.
authors.forename: Hamad B
authors.initials: HB
authors.lastname: Rashid
authors.affiliation: The Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush, Roslin, Midlothian, Edinburgh, Scotland, United Kingdom.
authors.forename: Michael
authors.initials: M
authors.lastname: Thrusfield
authors.affiliation: Division of Infection and Pathway Medicine, The University of Edinburgh Medical School, Edinburgh, Scotland, United Kingdom.
authors.forename: Sue
authors.initials: S
authors.lastname: Welburn
authors.affiliation: The University of Edinburgh, Roslin Institute at the R(D)SVS, Easter Bush, Roslin, Midlothian, Edinburgh, Scotland, United Kingdom.
authors.forename: Barend MdeC
authors.initials: BM
authors.lastname: Bronsvoort
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D016022:Case-Control Studies; D053127:Influenza A Virus, H9N2 Subtype / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control / Q000821:virology; D016015:Logistic Models; D010154:Pakistan; D011200:Poultry; D011201:Poultry Diseases / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control / Q000821:virology; D012307:Risk Factors