EFFECT OF DIFFERENT EAST-COAST FEVER CONTROL STRATEGIES ON DISEASE INCIDENCE IN TRADITIONALLY MANAGED SANGA CATTLE IN CENTRAL PROVINCE OF ZAMBIA

A clinical trial, including five East Coast fever (ECF) control strate gies (involving tick control and/or immunisation by infection-and-trea tment) in five different groups of traditionally managed Sanga cattle, was conducted in Central Province of Zambia over 2.5 years between 19 92 and 1995. Two groups were kept under intensive tick control by week ly acaricide treatment by hand spray; (one immunised and one non-immun ised), two groups were under no tick control (one immunised and one no n-immunised), and a fifth, immunised group was maintained under strate gic tick control (18 sprays yr(-1)). ECF-specific mortality was highes t in the non-immunised and non-treated group, while no difference in E CF-specific mortality could be observed between animals treated for EC F by immunisation or by tick control, Acaricide treatment and/or immun isation reduced the risk of clinical ECF by 92%. The results of an art ificial challenge experiment at the end of the field trial indicated t hat about 60% of the animals in the control group had become infected with Theileria parva without showing clinical signs. ECF incidence in non-vaccinated cattle markedly declined six months after immunisation- suggesting that the carrier state induced by immunisation did not lead to a persistent high incidence, and might accelerate the progress to endemicity. (C) 1998 Elsevier Science B.V.