Modelling the natural circulation of African Horse sickness in Zebra in the Western Cape province

  • Porphyre, Thibaud (Principal Investigator)
  • Grewar, John (Co-investigator)

Project Details


To model the natural circulation of African Horse sickness (AHS) in zebra and evaluate the potential of AHS to persist in the
African horse sickness controlled area’s population in the Western Cape Province.

Layman's description

The purpose of this research was to characterize the spread of African horse sickness (AHS) in populations of plain Zebra (Equus quagga) in the Western Cape Province (WCP) in order to feedback information to the South African horse industry on the potential of these populations to act as a wildlife reservoir of virus in the control and surveillance areas.
This research addresses three main objectives relevant to WCP and the understanding of AHS spread in plain Zebra:
Objective (i): Assess the high-risk period in which AHS will circulate persistently in WCP Zebra population
Objective (ii): Evaluate the risk of each holding in WCP to generate widespread and persistent circulation of AHS in Zebra
Objective (iii): Assess the required size of a Zebra population to allow persistent circulation of AHS in WCP

Key findings

The results of our analyses on the transmission and circulation of AHS in plain zebra in South Africa provided an improved understanding of how AHS virus spread in this wildlife population, particularly it clarified conditions in which incursions would persist and become endemic in zebra. Particularly, our results showed that:
- the population of plain zebras currently present in WCP are not sufficiently large for AHS incursion events to become endemic;
- the coastal populations in WCP need to be >2500 individuals for AHS to persist >2 years, even if zebras are infectious for more than 50days, on average;
- AHS cannot become endemic in the coastal population of WCP unless the zebra
population involves at least 50,000 individuals;
- inland populations of plain zebra in WCP may represent a risk for AHS to persist but would require a population of at least 500 zebras or show unrealistic duration of infectiousness for AHS incursion events to become endemic.
Effective start/end date1/08/189/11/18


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