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Home / Equine Research Bank / Transbound Emerg Dis / Establishing post-outbreak freedom from African horse sickne...
Transboundary and emerging diseases2019; 66(6); 2288-2296; doi: 10.1111/tbed.13279

Establishing post-outbreak freedom from African horse sickness virus in South Africa’s surveillance zone.

Abstract: An African horse sickness (AHS) outbreak occurred in South Africa's AHS controlled area in autumn 2016. A freedom from disease survey was performed to establish the likelihood of ongoing circulation of the associated virus during the same period the following year. A single-stage surveillance strategy was employed with a population-level design prevalence of 1% to establish a survey population sensitivity of 95% (probability that one or more positive horses would be detected if AHS was present at a prevalence greater than or equal to the design prevalence). In March 2017, a total of 262 randomly selected horses from 51 herds were sampled from the 2016 outbreak containment zone. Three within-herd and herd-level design prevalence scenarios were used in evaluating the post-survey probability of freedom. Depending on the underlying design prevalence scenarios, effectively ranging between 0.8% and 6.4%, and the use of informed or uninformed priors, the probability of freedom derived from this surveillance ranged between 73.1% and 99.9% (uninformed prior) and between 96.6% and 100% (informed prior). Based on the results, the authors conclude that it is unlikely that the 2016 AHS virus was still circulating in the autumn of 2017 in the 2016 outbreak containment zone. The ability to perform freedom from disease surveys, and also to include risk-based methods, in the AHS controlled area of South Africa is influenced by the changing underlying population at risk and the high level of vaccination coverage in the horse population. Ongoing census post-outbreak must be undertaken to maintain a valid sampling frame for future surveillance activity. The seasonality of AHS, the restricted AHS vaccination period and the inability to easily differentiate infected from vaccinated animals by laboratory testing impact the ability to perform a freedom from disease survey for AHS in the 12 months following an outbreak in the controlled area.
© 2019 Blackwell Verlag GmbH.
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Publication Date: 2019-07-07 PubMed ID: 31231964DOI: 10.1111/tbed.13279Google 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.

The research article presents an investigation into the aftermath of an African horse sickness virus (AHS) outbreak in South Africa in 2016. The study’s aim was to determine if the virus was still present a year later, using rigorous testing and analysis.

Background

  • Following an outbreak of AHS in South Africa’s AHS controlled area in 2016, the researchers initiated a freedom from disease survey in 2017.
  • The survey was aimed at identifying the potential presence or absence of the virus after one year.
  • A single-stage surveillance strategy was employed to capture as much relevant data as possible.

Methodology

  • In March 2017, researchers conducted a survey by selecting 262 horses from 51 herds within the containment zone of the 2016 outbreak.
  • The survey design was intended to have a 95% sensitivity. This means that the researchers were 95% sure that if the virus was present at a prevalence of 1% or more, it would be detected by the survey.
  • Three different prevalence scenarios were used to interpret the data from the survey.

Findings

  • Depending on the inherent prevalence of the disease and the choice of priors for statistical analysis, the probability that the surveyed area was free of the disease ranged between 73.1% and 99.9% for the uninformed prior, and between 96.6% and 100% for the informed prior.
  • The authors, based on these results, concluded that it was unlikely the AHS virus was still present in 2017 within the surveyed zone of the 2016 outbreak.

Implications and Limitations

  • Conducting such surveys depends heavily on the population at risk and high levels of vaccination coverage among the horse population.
  • Consistent monitoring after an outbreak is essential to maintain a valid sampling frame for future research efforts.
  • The efforts to detect the virus are impacted by the seasonality of AHS, the restricted AHS vaccination period, and the challenge to differentiate between infected and vaccinated horses through laboratory testing.
  • The outbreak in the controlled area complicates the process and affects the ability to confirm that the region is free from the disease.

Cite This Article

APA
Grewar JD, Sergeant ES, Weyer CT, van Helden LS, Parker BJ, Anthony T, Thompson PN. (2019). Establishing post-outbreak freedom from African horse sickness virus in South Africa’s surveillance zone. Transbound Emerg Dis, 66(6), 2288-2296. https://doi.org/10.1111/tbed.13279

Publication

Transboundary and emerging diseases
ISSN: 1865-1682
NlmUniqueID: 101319538
Country: Germany
Language: English
Volume: 66
Issue: 6
Pages: 2288-2296

Researcher Affiliations

Grewar, John Duncan
  • Epidemiology Section, Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa.
  • Equine Health Fund, Wits Health Consortium, Johannesburg, South Africa.
Sergeant, Evan S
  • AusVet Animal Health Services, Canberra, Australian Capital Territory, Australia.
Weyer, Camilla Theresa
  • Equine Health Fund, Wits Health Consortium, Johannesburg, South Africa.
van Helden, Lesley Susan
  • Western Cape Veterinary Services, Elsenburg, South Africa.
Parker, Beverley Joan
  • Equine Health Fund, Wits Health Consortium, Johannesburg, South Africa.
Anthony, Tasneem
  • Western Cape Veterinary Services, Elsenburg, South Africa.
Thompson, Peter Neil
  • Epidemiology Section, Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa.

MeSH Terms

  • African Horse Sickness / epidemiology
  • African Horse Sickness Virus
  • Animals
  • Disease Outbreaks / veterinary
  • Horses
  • Sentinel Surveillance / veterinary
  • South Africa / epidemiology

Grant Funding

  • EHF001 / Wits Health Consortium Pty Ltd, Equine Health Fund

References

This article includes 29 references
  1. Animal Diseases Act (Act No.35). (1984). Retrieved from http://www.daff.gov.za.
  2. Bosman P, Brückner GK, Faul A. African horse sickness surveillance systems and regionalisation/zoning: The case of South Africa. Revue Scientifique et Technique (International Office of Epizootics) 14(3), 645-653.
    doi: 10.20506/rst.14.3.866google scholar: lookup
  3. Cameron AR, Baldock FC. A new probability formula for surveys to substantiate freedom from disease. Preventive Veterinary Medicine 34(1), 1-17.
    doi: 10.1016/s0167-5877(97)00081-0google scholar: lookup
  4. Cameron AR, Baldock FC. Two-stage sampling in surveys to substantiate freedom from disease. Preventive Veterinary Medicine 34(1), 19-30.
    doi: 10.1016/s0167-5877(97)00073-1google scholar: lookup
  5. Camphor HS. Design of surveillance plans for Rift Valley fever in two different ecological zones in southern Africa (Masters dissertation). .
  6. Coetzer J, Guthrie AJ. African horse sickness. Infectious Diseases of Livestock 2nd ed., pp. 1231-1246.
  7. Diarmita IK. Self-declaration of an equine disease free zone in Jakarta, Indonesia, for the purpose of facilitating the equestrian competitions in the framework of the 18th Asian Games 2018. .
  8. EU. 2008/698/EC: Commission decision of 8 August 2008 on the temporary admission and imports into the Community of registered horses from South Africa. Official Journal of the European Union L.235(2.9.2008), 16-25.
  9. EU. Commission Implementing Regulation (EU) 2015/1375 of 10 August 2015 laying down specific rules on official controls for Trichinella in meat. Official Journal of the European Union L.212(11.8.2015), 7-34.
  10. Grewar JD. The economic impact of Bluetongue and other orbiviruses in sub-Saharan Africa, with special reference to Southern Africa. Veterinaria Italiana 52(3-4), 375-381.
    doi: 10.12834/vetit.503.2427.3google scholar: lookup
  11. Grewar JD, Weyer CT, Burger P, Russouw E, Parker BJ, Guthrie AJ. The AHS sentinel surveillance program: 2016-2017 season report. .
  12. Grewar JD, Weyer CT, Guthrie AJ, Koen P, Davey S, Quan M, Bührmann G. The 2011 outbreak of African horse sickness in the African horse sickness controlled area in South Africa. Journal of the South African Veterinary Association 84(1), 1-7.
    doi: 10.4102/jsava.v84i1.973google scholar: lookup
  13. Grewar JD, Weyer CT, Venter GJ, Helden LS, Burger P, Guthrie AJ, Thompson PN. A field investigation of an African horse sickness outbreak in the controlled area of South Africa in 2016. Transboundary and Emerging Diseases 66(2), 743-751.
    doi: 10.1111/tbed.13077google scholar: lookup
  14. Grigore M. Self-declaration by Romania on regaining its Bluetongue free status. .
  15. Guthrie AJ, MacLachlan NJ, Joone C, Lourens CW, Weyer CT, Quan M, Gardner IA. Diagnostic accuracy of a duplex real-time reverse transcription quantitative PCR assay for detection of African horse sickness virus. Journal of Virological Methods 189(1), 30-35.
    doi: 10.1016/j.jviromet.2012.12.014google scholar: lookup
  16. MacDiarmid SC. Future options for brucellosis surveillance in New Zealand beef herds. New Zealand Veterinary Journal 36(1), 39-42.
    doi: 10.1080/00480169.1988.35472google scholar: lookup
  17. Martin PAJ, Cameron AR, Barfod K, Sergeant ESG, Greiner M. Demonstrating freedom from disease using multiple complex data sources 2: Case study-Classical swine fever in Denmark. Preventive Veterinary Medicine 79(2-4), 98-115.
    doi: 10.1016/j.prevetmed.2006.09.007google scholar: lookup
  18. OIE. Infection with African horse sickness. Terrestrial Animal Health Code 25th edn.
  19. OIE. Bovine spongiform encephalopathy. Terrestrial Animal Health Code 27th edn.
  20. OIE. Infection with Brucella abortus, B. melitensis and B. suis. Terrestrial Animal Health Code 27th edn.
  21. Schulman ML, Marlow CHB, Nurton JP. A survey of reproductive success in South African Thoroughbred horse breeding from 1975 to 1999. Journal of the South African Veterinary Association 74(1), 17-19.
    doi: 10.4102/jsava.v74i1.492google scholar: lookup
  22. Sergeant ES, Grewar JD, Weyer CT, Guthrie AJ. Quantitative risk assessment for African horse sickness in live horses exported from South Africa. PLoS ONE 11(3), e0151757.
    doi: 10.1371/journal.pone.0151757google scholar: lookup
  23. Sinclair M, Bührmann G, Gummow B. An epidemiological investigation of the African horsesickness outbreak in the Western Cape Province of South Africa in 2004 and its relevance to the current equine export protocol. Journal of the South African Veterinary Association 77, 191-196.
    doi: 10.4102/jsava.v77i4.376google scholar: lookup
  24. Stärk KD, Regula G, Hernandez J, Knopf L, Fuchs K, Morris RS, Davies P. Concepts for risk-based surveillance in the field of veterinary medicine and veterinary public health: Review of current approaches. BMC Health Services Research 6(1), 20.
    doi: 10.1186/1472-6963-6-20google scholar: lookup
  25. Stokes JE, Baylis M, Duncan JS. A freedom from disease study: Schmallenberg virus in the south of England in 2015. The Veterinary Record 179(17), 435.
    doi: 10.1136/vr.103903google scholar: lookup
  26. Tratalos JA, Barrett DJ, Clegg TA, O’Neill RG, McGrath G, Lane EA, More SJ. Sampling methodology to maximize the efficient use of national abattoir surveillance: Using archived sera to substantiate freedom from bluetongue virus infection in Ireland. Frontiers in Veterinary Science 5.
    doi: 10.3389/fvets.2018.00261google scholar: lookup
  27. Vallat B. The OIE recognition of country sanitary status for freedom from diseases [Editorial]. OIE: Editorials from the Director General .
  28. Weyer CT, Grewar JD, Burger P, Rossouw E, Lourens C, Joone C, Guthrie AJ. African horse sickness caused by genome reassortment and reversion to virulence of live, attenuated vaccine viruses, South Africa, 2004-2014. Emerging Infectious Diseases 22(12), 2087-2096.
    doi: 10.3201/eid2212.160718google scholar: lookup
  29. Weyer CT, Joone C, Lourens CW, Monyai MS, Koekemoer O, Grewar JD, Guthrie AJ. Development of three triplex real-time reverse transcription PCR assays for the qualitative molecular typing of the nine serotypes of African horse sickness virus. Journal of Virological Methods 223, 69-74.
    doi: 10.1016/j.jviromet.2015.07.015google scholar: lookup

Citations

This article has been cited 1 times.
  1. Clemmons EA, Alfson KJ, Dutton JW 3rd. Transboundary Animal Diseases, an Overview of 17 Diseases with Potential for Global Spread and Serious Consequences. Animals (Basel) 2021 Jul 8;11(7).
    doi: 10.3390/ani11072039pubmed: 34359167google scholar: lookup
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