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Prevalence of and risk factors associated with ovine progressive pneumonia in Wyoming sheep flocks

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  • 1 Wyoming State Veterinary Laboratory, Department of Veterinary Sciences, University of Wyoming, Laramie, WY 82070.
  • | 2 Wyoming State Veterinary Laboratory, Department of Veterinary Sciences, University of Wyoming, Laramie, WY 82070.
  • | 3 USDA APHIS Veterinary Services, 3921 Gannett St, Casper, WY 82609.
  • | 4 Wyoming State Veterinary Laboratory, Department of Veterinary Sciences, University of Wyoming, Laramie, WY 82070.
  • | 5 Science Technology and Analysis Services, USDA APHIS Veterinary Services, 2150 Centre Ave, Building B, NRRC, MS2E7, Fort Collins, CO 80525.
  • | 6 Wyoming Livestock Board, 1934 Wyott Dr, Cheyenne, WY 82002.
  • | 7 Wyoming State Veterinary Laboratory, Department of Veterinary Sciences, University of Wyoming, Laramie, WY 82070.

Abstract

Objective—To determine the prevalence of antibodies against small ruminant lentivirus (SRLV), the causative agent of ovine progressive pneumonia (OPP), and to identify risk factors associated with OPP in Wyoming sheep flocks.

Design—Cross-sectional study.

Animals—1,415 sheep from 54 flocks in Wyoming.

Procedures—Flocks were surveyed as part of the National Animal Health Monitoring System (NAHMS) 2011 sheep study. Serum samples obtained from sheep in Wyoming were analyzed for anti-SRLV antibodies by use of a competitive-inhibition ELISA. The prevalence of seropositive animals overall and within each flock was calculated. Respective associations between flock OPP status and various demographic and management variables were assessed.

Results—The estimated prevalence of sheep seropositive for anti-SRLV antibodies and OPP-infected flocks in Wyoming was 18.0% and 47.5%, respectively. Within OPP-infected flocks, the prevalence of seropositive sheep ranged from 3.9% to 96%. Flocks maintained on nonfenced range were more likely to be infected with OPP than were flocks maintained on fenced range (OR, 3.4; 95% confidence interval, 1.1 to 10.7). The estimated prevalence of OPP-infected flocks in Wyoming did not vary substantially from that at the regional or national level reported in the NAHMS 2001 sheep study. Compared with results of the NAHMS 2011 sheep study, Wyoming producers were more familiar with OPP than were other US sheep producers, but only 61% of Wyoming producers surveyed reported being very or somewhat familiar with the disease.

Conclusions and Clinical Relevance—Results indicated that OPP is prevalent in many Wyoming sheep flocks, which suggested that continued efforts are necessary to increase producer knowledge about the disease and investigate practices to minimize economic losses associated with OPP.

Abstract

Objective—To determine the prevalence of antibodies against small ruminant lentivirus (SRLV), the causative agent of ovine progressive pneumonia (OPP), and to identify risk factors associated with OPP in Wyoming sheep flocks.

Design—Cross-sectional study.

Animals—1,415 sheep from 54 flocks in Wyoming.

Procedures—Flocks were surveyed as part of the National Animal Health Monitoring System (NAHMS) 2011 sheep study. Serum samples obtained from sheep in Wyoming were analyzed for anti-SRLV antibodies by use of a competitive-inhibition ELISA. The prevalence of seropositive animals overall and within each flock was calculated. Respective associations between flock OPP status and various demographic and management variables were assessed.

Results—The estimated prevalence of sheep seropositive for anti-SRLV antibodies and OPP-infected flocks in Wyoming was 18.0% and 47.5%, respectively. Within OPP-infected flocks, the prevalence of seropositive sheep ranged from 3.9% to 96%. Flocks maintained on nonfenced range were more likely to be infected with OPP than were flocks maintained on fenced range (OR, 3.4; 95% confidence interval, 1.1 to 10.7). The estimated prevalence of OPP-infected flocks in Wyoming did not vary substantially from that at the regional or national level reported in the NAHMS 2001 sheep study. Compared with results of the NAHMS 2011 sheep study, Wyoming producers were more familiar with OPP than were other US sheep producers, but only 61% of Wyoming producers surveyed reported being very or somewhat familiar with the disease.

Conclusions and Clinical Relevance—Results indicated that OPP is prevalent in many Wyoming sheep flocks, which suggested that continued efforts are necessary to increase producer knowledge about the disease and investigate practices to minimize economic losses associated with OPP.

Contributor Notes

Ms. Gerstner's present address is Hawthorne Animal Hospital, 5011 Hawthorne Rd, Pocatello, ID 83202.

Dr. Adamovicz's present address is Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211.

Serum samples from the animals described in the study reported here were evaluated at the Wyoming State Veterinary Laboratory.

The authors declare that they have no conflicts of interest or additional sources of funding.

The authors thank Dr. Michael McDole and Sherry Healey for technical assistance.

Address correspondence to Dr. Schumaker (bschumak@uwyo.edu).