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Evaluation of risk factors for the spread of low pathogenicity H7N2 avian influenza virus among commercial poultry farms

Dr. Jennifer H. McQuistonUnited States Public Health Service, Commissioned Corps Readiness Force, CDC, 1600 Clifton Rd MS G-44, Atlanta, GA 30333.

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Lindsey P. GarberUSDA, Animal and Plant Health Inspection Service (APHIS), Veterinary Services (VS), Centers for Epidemiology and Animal Health, 2150 Centre Ave, Bldg B, Fort Collins, CO 80526.

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Barbara A. Porter-SpaldingUSDA, APHIS, VS, Eastern Regional Office, 920 Main Campus Dr, Ste 200, Raleigh, NC 27606.

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John W. HahnUSDA, APHIS, VS, Arkansas Area Office, 1200 Cherry Brook Dr, Ste 300, Little Rock, AR 72211.

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F. William PiersonCenter for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA 24061.

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Sherrilyn H. WainwrightUSDA, Animal and Plant Health Inspection Service (APHIS), Veterinary Services (VS), Centers for Epidemiology and Animal Health, 2150 Centre Ave, Bldg B, Fort Collins, CO 80526.

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Dennis A. SenneUSDA, APHIS, VS, National Veterinary Services Laboratory, 1800 Dayton Ave, Ames, IA 50010.

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Thomas J. BrignoleUSDA, APHIS, VS, Eastern Regional Office, 920 Main Campus Dr, Ste 200, Raleigh, NC 27606.

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Dr. Bruce L. AkeyOffice of Laboratory Services, Virginia Department of Agriculture and Consumer Services, 1100 Bank St, Richmond, VA 23219.
present address is the New York State Department of Agriculture and Markets, Division of Animal Industry, 1 Winners Cir, Albany, NY 12235.

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Thomas J. HoltUSDA, APHIS, VS, Eastern Regional Office, 920 Main Campus Dr, Ste 200, Raleigh, NC 27606.

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Abstract

Objective—To identify risk factors associated with the spread of low pathogenicity H7N2 avian influenza (AI) virus among commercial poultry farms in western Virginia during an outbreak in 2002.

Design—Case-control study.

Procedure—Questionnaires were used to collect information about farm characteristics, biosecurity measures, and husbandry practices on 151 infected premises (128 turkey and 23 chicken farms) and 199 noninfected premises (167 turkey and 32 chicken farms).

Results—The most significant risk factor for AI infection was disposal of dead birds by rendering (odds ratio [OR], 7.3). In addition, age ≥ 10 weeks (OR for birds aged 10 to 19 weeks, 4.9; OR for birds aged ≥ 20 weeks, 4.3) was a significant risk factor regardless of poultry species involved. Other significant risk factors included use of nonfamily caretakers and the presence of mammalian wildlife on the farm. Factors that were not significantly associated with infection included use of various routine biosecurity measures, food and litter sources, types of domestic animals on the premises, and presence of wild birds on the premises.

Conclusions and Clinical Relevance—Results suggest that an important factor contributing to rapid early spread of AI virus infection among commercial poultry farms during this outbreak was disposal of dead birds via rendering off-farm. Because of the highly infectious nature of AI virus and the devastating economic impact of outbreaks, poultry farmers should consider carcass disposal techniques that do not require offfarm movement, such as burial, composting, or incineration. (J Am Vet Med Assoc 2005;226:767–772)

Abstract

Objective—To identify risk factors associated with the spread of low pathogenicity H7N2 avian influenza (AI) virus among commercial poultry farms in western Virginia during an outbreak in 2002.

Design—Case-control study.

Procedure—Questionnaires were used to collect information about farm characteristics, biosecurity measures, and husbandry practices on 151 infected premises (128 turkey and 23 chicken farms) and 199 noninfected premises (167 turkey and 32 chicken farms).

Results—The most significant risk factor for AI infection was disposal of dead birds by rendering (odds ratio [OR], 7.3). In addition, age ≥ 10 weeks (OR for birds aged 10 to 19 weeks, 4.9; OR for birds aged ≥ 20 weeks, 4.3) was a significant risk factor regardless of poultry species involved. Other significant risk factors included use of nonfamily caretakers and the presence of mammalian wildlife on the farm. Factors that were not significantly associated with infection included use of various routine biosecurity measures, food and litter sources, types of domestic animals on the premises, and presence of wild birds on the premises.

Conclusions and Clinical Relevance—Results suggest that an important factor contributing to rapid early spread of AI virus infection among commercial poultry farms during this outbreak was disposal of dead birds via rendering off-farm. Because of the highly infectious nature of AI virus and the devastating economic impact of outbreaks, poultry farmers should consider carcass disposal techniques that do not require offfarm movement, such as burial, composting, or incineration. (J Am Vet Med Assoc 2005;226:767–772)