East Coast Fever spreads

Devastating livestock disease East Coast Fever (ECF), carried by the brown ear tick, is on the rise in Southern Africa.
Dr Jane Olwoch of the University of Pretoria has been researching causes and solutions – she told Annelie Coleman
Issue date 9 November 2007

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“There should be no reason for the RISE in East Coast Fever (ECF), given all the new patent tick-killing chemicals, but it’s spreading nonetheless,” says Jane Olwoch, an environmental scientist at the University of Pretoria. “The reason is a shift in seasonal climatic conditions. Short or mild winters shorten the ticks’ life cycles, significantly increasing their numbers.” S cientifically known as Theileriosis – the protozoan pathogen that causes the disease is called Theileria parva – ECF is transmitted by a tick commonly known as the brown ear tick, which attaches itself inside livestock’s ears, particularly cattle. Symptoms include high fever, diarrhoea, a drop in milk yield, nasal and eye discharge, emaciation and enlarged lymph nodes. In 90% of cases death occurs after seven to 10 days.

Is one of the most common and devastating livestock diseases in eastern and southern Africa, spreading south from southern Sudan to the eastern parts of SA and as far west as the DRC. A ccording to the agriculture department, SA’s first recorded ECF outbreak was in the former Transvaal in 1902. It’s believed to have been introduced from then Tanganyika by cattle infected along the coast before shipment to Lourenço Marques (Maputo), and was introduced into Natal soon afterwards, probably via Swaziland. It was kept out of the Cape until 1910, when it suddenly appeared on the Umzimkulu commonage, spreading rapidly, and doing considerable damage. D r Olwoch says her research shows the spread of the disease can be ascribed to the growing number of private game farms in proximity to livestock farms, as well as climate change. Many game species, such as buffalo and antelopes, are brown ear tick carriers. Small mammals are increasingly acting as carriers, as habitat fragmentation has reduced the numbers of big mammals. ECF is spreading rapidly, despite the use of acaricides and other control measures, as ticks develop increasing resistance. Cases have been reported in the Eastern Cape and Limpopo where never occurred before.

The disease usually peaks in January and March but there are now additional peaks in November and December. “It’s possible that other areas are experiencing the same increases,” says Dr Olwoch. “The entire country must be regularly sampled.” ECF research The disease is spread through blood drawn by brown ear tick bites. As a three-host tick, the brown ear’s different instars (larva, nymphs and adults) can use three different types of hosts. “If a larva feeds on an animal that has the parasites, it transmits the infection as a nymph when it feeds on another animal,” explains Dr Olwoch. “An infected nymph transmits the infection as an adult. Olwoch’s research looks at the impact of climate change on ticks, tick-borne diseases and host animals. “I have to look at the whole system of vector-host-disease,” she says. “It’s complex but vital to understand, particularly since our environment is changing, the population is growing and the climate is changing. Climate and

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