With winter looming and rainfall patterns changing, the threat of further outbreaks of African horse sickness (AHS) this season is expected to dissipate. Favourable climatic conditions in summer rainfall regions increased the breeding and spread of the Culicoides fly, which acts as vector and spreads AHS. Higher than average rainfall occurred in Gauteng, northern Limpopo, KwaZulu-Natal, parts of the Northern Cape, the southern region of the Eastern Cape and the western region of the Western Cape from July to October 2012.
Last week, the movement of horses into the Western Cape was restricted. The chief director of veterinary services in the province, Dr Gininda Msiza, said restrictions were placed on all direct movements into the AHS Control Area from other provinces in South Africa. Wouter Kriel, spokesperson for the Western Cape agriculture MEC, Gerrit van Rensburg, said a buffer zone extending from Atlantis towards Cape Town had been set up to reduce the risk of infected animals contaminating the AHS-free zone.
The rest of the province was declared a control area, and demarcated with signs along major access routes into the Western Cape including the N1 between Laingsburg and Touws River, the N2 at Suurbraak, the N7 at Trawal and outside Barrydale on the R62. Dr Grietjie de Klerk, chief state veterinarian: Epidemiology, Directorate: Animal Health of the Department of Agriculture, Forestry and Fisheries, said the first outbreaks of the season started in North West, Mpumalanga, Gauteng, KZN and the Free State from October to December 2012.
It then spread to the Eastern Cape and the eastern parts of the Western Cape during January and February 2013. In 2011, when AHS was extremely severe, more than 300 cases were reported nationally, with a total of 146 recorded so far in the 2013 season,” said De Klerk “The outbreaks in the 2013 season reached a peak in January with a steady decline in the February to mid-March period. The 2011 and 2012 seasons reached a peak only in March with a sharp decline in the April and May period. The outbreaks in the KZN Midlands follow the route of the N3 highway,” she said.
De Klerk said the reason for this was unknown. “But one can speculate that more equine locations are situated along the main routes and/or reporting of outbreaks is more convenient if the location is closer to main routes. It is also possible that the route contributes to the distribution, as horses in the incubation phase or early stage of disease might be moved along the route,” De Klerk said.
Buffalo City State Veterinarian, Dr Stuart Varrie, said the situation in the Eastern Cape was profoundly exacerbated by the large number of horses, in relatively close proximity, that had never been vaccinated, or were vaccinated irregularly.
“It is especially this group of horses we were primarily concerned about and thus the distribution of vaccine was critical. The vaccine distributed was supplied in part by the state (250 doses), the African Horse Sickness Trust (250 doses) and the Equine Research Centre of the University of Pretoria (100 doses).
“The remaining vaccine was made available for free to private owners who had limited numbers of horses and had approached the state veterinary office directly or through private veterinarians. These owners were unable to vaccinate their horses for economic reasons,” he said.
Dr Jane Pistorius, manager of the veterinary services western region of the Eastern Cape, said the only case reported in their area, a death at a race course in Port Elizabeth, was a horse infected in KZN and transported during the incubation phase.