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Journal of the American Veterinary Medical Association2004; 225(7); 1084-1089; doi: 10.2460/javma.2004.225.1084

Evaluation of an outbreak of West Nile virus infection in horses: 569 cases (2002).

Abstract: To characterize an outbreak of West Nile virus (WNV) infection in horses in North Dakota in 2002, evaluate vaccine effectiveness, and determine horse characteristics and clinical signs associated with infection. Methods: Retrospective study. Methods: 569 horses. Methods: Data were obtained from veterinary laboratory records, and a questionnaire was mailed to veterinarians of affected horses. Results: Affected horses were defined as horses with typical clinical signs and seroconversion or positive results of virus isolation; affected horses were detected in 52 of the 53 counties and concentrated in the eastern and northeastern regions of the state. Among affected horses, 27% (n = 152) were vaccinated against WNV, 54% (309) were not, and 19% (108) had unknown vaccination status; 61 % (345) recovered, 22% (126) died, and 17% (98) had unknown outcome. The odds of death among nonvaccinated horses were 3 and 16 times the odds among horses that received only 1 or 2 doses of vaccine and horses that were vaccinated according to manufacturer's recommendations, respectively. Horses with recumbency, caudal paresis, and age > 5 years had higher odds of death, whereas horses with incoordination had lower odds of death, compared with affected horses without these characteristics. Conclusions: Vaccination appears to have beneficial effects regarding infection and death caused by WNV.
Publication Date: 2004-11-02 PubMed ID: 15515988DOI: 10.2460/javma.2004.225.1084Google Scholar: Lookup
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  • Evaluation Study
  • Journal Article
  • Research Support
  • Non-U.S. Gov't
  • Research Support
  • U.S. Gov't
  • Non-P.H.S.

Summary

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This research examines an outbreak of West Nile virus in horses in North Dakota in 2002, looking at the effectiveness of vaccines and the characteristics of the horses that affected the infection.

Methodology

  • The researchers employed a retrospective study design to evaluate the 2002 outbreak.
  • The sample involved in this study was made up of 569 horses.
  • Information was gathered from veterinary laboratory records, with additional data obtained using a questionnaire mailed to the veterinarians responsible for the affected horses.

Results

  • The affected horses, identified through clinical signs and seroconversion or positive virus isolation, were found in 52 of the 53 counties in North Dakota.
  • These horses were mostly located in the eastern and northeastern regions of the state.
  • Horses that had been vaccinated against West Nile virus comprised 27% of the sample, 54% were unvaccinated, and for 19% the vaccination status was unknown.
  • Regarding the recovery rate, 61% of the horses recovered from the virus, 22% died, and for 17% the outcome was unknown.
  • Non-vaccinated horses were found to have odds of death 3 to 16 times higher than horses who had received one or two doses of the vaccine, and horses who had been vaccinated according to the manufacturer’s recommendations.
  • Horses over the age of 5, those exhibiting signs of recumbency, or caudal paresis had higher odds of death, while horses with incoordination were found to have lower odds of death compared to affected horses not manifesting these characteristics.

Conclusions

  • The study concluded that vaccination seemed to offer significant protection against both infection and death from West Nile virus.

Cite This Article

APA
Schuler LA, Khaitsa ML, Dyer NW, Stoltenow CL. (2004). Evaluation of an outbreak of West Nile virus infection in horses: 569 cases (2002). J Am Vet Med Assoc, 225(7), 1084-1089. https://doi.org/10.2460/javma.2004.225.1084

Publication

ISSN: 0003-1488
NlmUniqueID: 7503067
Country: United States
Language: English
Volume: 225
Issue: 7
Pages: 1084-1089

Researcher Affiliations

Schuler, Larry A
  • North Dakota State Board of Animal Health, 600 E Boulevard Ave, Dept 602, Bismarck, ND 58505-0020, USA.
Khaitsa, Margaret L
    Dyer, Neil W
      Stoltenow, Charles L

        MeSH Terms

        • Animals
        • Disease Outbreaks / veterinary
        • Female
        • Horse Diseases / epidemiology
        • Horse Diseases / mortality
        • Horse Diseases / prevention & control
        • Horses
        • Male
        • North Dakota / epidemiology
        • Retrospective Studies
        • Survival Analysis
        • Vaccination / veterinary
        • Viral Vaccines / administration & dosage
        • West Nile Fever / epidemiology
        • West Nile Fever / mortality
        • West Nile Fever / prevention & control
        • West Nile Fever / veterinary
        • West Nile virus / immunology

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