The 2011 outbreak of African horse sickness in the African horse sickness controlled area in South Africa

African horse sickness (AHS) is a controlled animal disease in South Africa, and as a result of the high mortality rates experienced, outbreaks in the AHS controlled area in the Western Cape Province have a significant impact on affected properties as well as on the exportation of live horses from the AHS free zone in metropolitan Cape Town. An outbreak of AHS serotype 1 occurred in the surveillance zone of the AHS controlled area of the Western Cape during the summer of 2011. The epicentre of the outbreak was the town of Mamre in the magisterial district of Malmesbury and the outbreak was confined to a defined containment zone within this area by movement control of all equids and a blanket vaccination campaign. A total of 73 cases of AHS were confirmed during this outbreak, which included four confirmed subclinical cases. The morbidity rate for the outbreak was 16% with a mortality rate of 14% and a case fatality rate of 88%. Outbreak disease surveillance relied on agent identification using polymerase chain reaction (PCR)-based assays, which is novel for an AHS outbreak in South Africa. The source of this outbreak was never confirmed although it is believed to be associated with the illegal movement of an infected animal into the Mamre area. This detailed description of the outbreak provides a sound scientific basis to assist decision making in future AHS outbreaks in the AHS controlled area of South Africa and in countries where AHS is an exotic or emerging disease.http://www.jsava.co.zaam2014ab201

A field investigation of an African horse sickness outbreak in the controlled area of South Africa in 2016

An outbreak of African horse sickness (AHS) caused by AHS virus type 1 occurred within the South African AHS surveillance zone during April and May 2016. The index case was detected by a private veterinarian through passive surveillance. There were 21 cases in total, which is relatively low compared to case totals during prior AHS outbreaks in the same region (and of the same AHS virus type) in 2004, 2011 and 2014. The affected proportion of horses on affected properties was 0.07 (95% CI 0.04, 0.11). Weather conditions were conducive to high midge activity immediately prior to the outbreak but midge numbers decreased rapidly with the advent of winter. The outbreak was localized, with 18 of the 21 cases occurring within 8 km of the index property and the three remaining cases on two properties within 21 km of the index property, with direction of spread consistent with wind‐borne dispersion of infected midges. Control measures included implementation of a containment zone with movement restrictions on equids. The outbreak was attributed to a reversion to virulence of a live attenuated vaccine used extensively in South Africa. Outbreaks in the AHS control zones have a major detrimental impact on the direct export of horses from South Africa, notably to the European Union.The Equine Health Fund–Wits Health Consortium (Pty) Ltd and the Equine Research Centre (University of Pretoria).http://wileyonlinelibrary.com/journal/tbed2020-03-01hj2020Equine Research CentreProduction Animal Studie