Control of Amblyomma variegatum and dermatophilosis on local and exotic breeds of cattle in Ghana.

The occurrence of dermatophilosis on cattle in the tropics is closely associated with infestation by Amblyomma variegatum ticks. Animals that are more susceptible to the disease also tend to carry higher tick burdens. Longitudinal studies carried out on the Accra Plains suggest that N'Dama cattle acquire an enhanced degree of resistance to these ticks following initial exposure. Lesions on zebu-type Ghana Sanga cattle tend to be confined to the predilection feeding sites of adult A. variegatum even when relatively large numbers of ticks are present suggesting that these cattle are able to contain the effects of the tick. Further studies are required to investigate the nature of the apparent resistance of indigenous cattle to the tick and/or its effects and the potential for controlling the disease by immunoprophylaxis using tick derived immunogens. Current methods of controlling the disease depend on the control of ticks using chemical acaricides. Susceptibility to A. variegatum associated dermatophilosis varies between breeds of cattle therefore the level of tick control required is breed dependant. Rigorous tick control is necessary for the prevention of dermatophilosis on highly susceptible exotic breeds of cattle. The limited use of acaricides applied either at the predilection feeding sites of A. variegatum and/or at selected times when the level of challenge increases is sufficient to control the occurrence of the disease on indigenous cattle.