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Veterinary research2007; 38(1); 109-116; doi: 10.1051/vetres:2006045

Incidence and effects of West Nile virus infection in vaccinated and unvaccinated horses in California.

Abstract: A prospective cohort study was used to estimate the incidence of West Nile virus (WNV) infection in a group of unvaccinated horses (n = 37) in California and compare the effects of natural WNV infection in these unvaccinated horses to a group of co-mingled vaccinated horses (n = 155). Horses initially were vaccinated with either inactivated whole virus (n = 87) or canarypox recombinant (n = 68) WNV vaccines during 2003 or 2004, prior to emergence of WNV in the region. Unvaccinated horses were serologically tested for antibodies to WNV by microsphere immunoassay incorporating recombinant WNV E protein (rE MIA) in December 2003, December 2004, and every two months thereafter until November 2005. Clinical neurologic disease attributable to WNV infection (West Nile disease (WND)) developed in 2 (5.4%) of 37 unvaccinated horses and in 0 of 155 vaccinated horses. One affected horse died. Twenty one (67.7%) of 31 unvaccinated horses that were seronegative to WNV in December, 2004 seroconverted to WNV before the end of the study in November, 2005. Findings from the study indicate that currently-available commercial vaccines are effective in preventing WND and their use is financially justified because clinical disease only occurred in unvaccinated horses and the mean cost of each clinical case of WND was approximately 45 times the cost of a 2-dose WNV vaccination program.
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Publication Date: 2007-02-06 PubMed ID: 17274156DOI: 10.1051/vetres:2006045Google Scholar: Lookup
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  • Controlled Clinical Trial
  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article discusses a study that was conducted to compare the incidence and effects of West Nile virus (WNV) infection in vaccinated and unvaccinated horses in California. The results indicate that commercially available vaccines are effective in preventing the disease and are financially justified given the cost of treating a clinical case of the disease.

Study Design

  • The study undertaken was a prospective cohort study. In this research design, a group of subjects, in this case, horses, are observed over a period of time to determine the probability of developing a particular disease, West Nile virus in this context.
  • The study population involved a group of unvaccinated horses (37 in number) and a larger group of vaccinated horses (155 in number).
  • The vaccinated horses had received either the inactivated whole virus vaccine or the canarypox recombinant West Nile virus vaccine in 2003 or 2004, before the virus emerged in the region.

Methodology and Findings

  • The unvaccinated horses were tested for antibodies to WNV using a microsphere immunoassay that included recombinant WNV E protein.
  • These tests were conducted in December 2003, December 2004, and then every two months until November 2005.
  • The results showed that West Nile disease (WND), a neurologic disease caused by WNV infection, developed in 2 out of the 37 unvaccinated horses. None of the vaccinated horses developed the disease.
  • In addition, 21 out of the 31 unvaccinated horses that initially had no antibodies to WNV, developed them by the end of the study in November 2005, indicating they had been infected with WNV.

Implications and Conclusions

  • Findings from the study point towards the effectiveness of commercially available vaccines in preventing WND. This is especially noteworthy considering a clinical manifestation of the disease only occurred in the unvaccinated batch of horses.
  • The study also suggested the financial justifications of using the vaccines. It was found that the cost of treating a clinical case of WND was approximately 45 times the cost of a 2-dose WNV vaccination program.
  • Thus, the study underscores the importance of vaccination programs in preventing WNV infection in horses, leading to significant savings in treatment costs and potentially reducing morbidity and mortality rates associated with the disease.

Cite This Article

APA
Gardner IA, Wong SJ, Ferraro GL, Balasuriya UB, Hullinger PJ, Wilson WD, Shi PY, MacLachlan NJ. (2007). Incidence and effects of West Nile virus infection in vaccinated and unvaccinated horses in California. Vet Res, 38(1), 109-116. https://doi.org/10.1051/vetres:2006045

Publication

Veterinary research
ISSN: 0928-4249
NlmUniqueID: 9309551
Country: England
Language: English
Volume: 38
Issue: 1
Pages: 109-116

Researcher Affiliations

Gardner, Ian A
  • Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Wong, Susan J
    Ferraro, Gregory L
      Balasuriya, Udeni B
        Hullinger, Pamela J
          Wilson, W David
            Shi, Pei-Yong
              MacLachlan, N James

                MeSH Terms

                • Animals
                • California / epidemiology
                • Cohort Studies
                • Horse Diseases / epidemiology
                • Horse Diseases / immunology
                • Horse Diseases / prevention & control
                • Horse Diseases / virology
                • Horses
                • Incidence
                • Time Factors
                • Viral Vaccines / administration & dosage
                • Viral Vaccines / immunology
                • West Nile Fever / epidemiology
                • West Nile Fever / immunology
                • West Nile Fever / prevention & control
                • West Nile Fever / veterinary

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