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The Onderstepoort journal of veterinary research2017; 84(1); e1-e5; doi: 10.4102/ojvr.v84i1.1445

The sero-prevalence and sero-incidence of African horse sickness and equine encephalosis in selected horse and donkey populations in Zimbabwe.

Abstract: Sentinel herds and samples submitted by private equine practitioners were used to determine the sero-prevalence and sero-incidence of African horse sickness virus (AHSV) and equine encephalosis virus (EEV) in horse and donkey populations in the Highveld region of Zimbabwe. The sero-prevalence and sero-incidence of antibodies against these viruses were determined using the competitive enzyme-linked immunosorbent assay (ELISA) for the detection of serum antibodies. In donkeys, the median sero-prevalence of AHSV antibodies, across the three rainy seasons under study, was 75% (inter quartile range [IQR] 67-83), with a seasonal median sero-incidence of 45% (IQR 40-63). In horses, the median sero-prevalence of EEV antibodies was 63% (IQR 21-73), with a median seasonal sero-incidence of 10.5% (IQR 10-14), while in donkeys the median sero-prevalence of EEV antibodies was 80% (IQR 67-90), with a median seasonal sero-incidence of 50% (IQR 40-60). This study highlighted the significant levels of exposure of donkeys to AHSV and horses and donkeys to EEV in Zimbabwe despite equine encephalosis remaining unreported by Zimbabwean veterinarians to date. Most seroconversions in sentinel herd animals to AHSV and EEV occurred towards the end of the rainy season in March, April and May corresponding to the time of the year when the Culicoides vectors are in high abundance. In order to determine the clinical significance of these infections, blood and spleen samples, submitted by private equine veterinary practitioners over a 5-year period, from horses showing characteristic clinical signs of African horse sickness were tested for the presence of viral antigen using the antigen capture ELISA. The median sero-prevalence of AHSV antigen in horses recorded from these samples was 38% (IQR 33-88). The predominant AHSV antigen from these samples was serotype 7 (33%) followed by serotype 2 (26%) and serotypes 4 and 8 (16% each). African horse sickness virus serotypes 3 and 9, identified in this study, had not been previously reported in Zimbabwe.
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Publication Date: 2017-05-10 PubMed ID: 28582979PubMed Central: PMC6238669DOI: 10.4102/ojvr.v84i1.1445Google Scholar: Lookup
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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.

This research investigated the presence and incidence of African horse sickness and equine encephalosis in horse and donkey populations in Zimbabwe, particularly during its rainy seasons. Using samples from private equine practitioners and targeted herds, the researchers concluded that the animals had significant exposure to these diseases, particularly towards the rainy season’s end when disease-carrying insects are in higher numbers.

Research Context and Goals

  • The study aims to measure the level of AHSV (African Horse Sickness Virus) and EEV (Equine Encephalosis Virus) prevalence and incidence in horse and donkey populations in the Highveld region of Zimbabwe.
  • The presence of these viruses in animals’ blood was identified by testing the interactions of competitive enzymes with serum antibodies in infected individuals:

Methodology

  • Researchers used the ELISA (Enzyme Linked Immunosorbent Assay) method to detect serum antibodies against AHSV and EEV.
  • Samples for this research were collected from targeted herds specifically chosen for monitoring (sentinel herds) and individual cases submitted by private equine practitioners.

Findings

  • The findings revealed that a significant proportion of donkeys was exposed to AHSV, while both horses and donkeys showed high exposure to EEV, despite equine encephalosis being unreported by Zimbabwean veterinarians.
  • The study also found that seroconversion, a point when measurable antibodies develop and become detectable, mostly occurred towards the rainy season’s end when disease-carrying vectors are most abundant.
  • The study found significant levels of AHSV and EEV, especially towards the end of the rainy seasons, corresponding to the period when Culicoides (a genus of biting flies) vectors were in high abundance.

Additional Testing and Results

  • Further to their sero-prevalence study, the researchers tested blood and spleen samples from horses showcasing typical AHSV symptoms.
  • These samples, again provided by private equine practitioners over five years, were tested for AHSV antigen presence, with just under half of the samples tested coming back positive.
  • The most common AHSV serotype identified was serotype 7, followed by serotype 2 and serotypes 4 and 8.
  • The study also identified serotypes 3 and 9, which had not been previously reported in Zimbabwe, suggesting the landscape of virus serotypes in the country might be broader than previously considered.

Cite This Article

APA
Gordon SJG, Bolwell C, Rogers CW, Musuka G, Kelly P, Guthrie A, Mellor PS, Hamblin C. (2017). The sero-prevalence and sero-incidence of African horse sickness and equine encephalosis in selected horse and donkey populations in Zimbabwe. Onderstepoort J Vet Res, 84(1), e1-e5. https://doi.org/10.4102/ojvr.v84i1.1445

Publication

The Onderstepoort journal of veterinary research
ISSN: 2219-0635
NlmUniqueID: 0401107
Country: South Africa
Language: English
Volume: 84
Issue: 1
Pages: e1-e5

Researcher Affiliations

Gordon, Stuart J G
  • Institute of Veterinary, Animal and Biomedical Sciences, Massey University. S.J.G.Gordon@massey.ac.nz.
Bolwell, Charlotte
    Rogers, Chris W
      Musuka, Godfrey
        Kelly, Patrick
          Guthrie, Alan
            Mellor, Philip S
              Hamblin, Christopher

                MeSH Terms

                • African Horse Sickness / epidemiology
                • African Horse Sickness Virus / immunology
                • Animals
                • Antibodies, Viral / blood
                • Equidae
                • Horses
                • Incidence
                • Prevalence
                • Zimbabwe / epidemiology

                Grant Funding

                • Wellcome Trust

                Conflict of Interest Statement

                The authors declare that they have no financial or personal relationships which may have inappropriately influenced them in writing this article.

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                Citations

                This article has been cited 6 times.
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