CORRELATION BETWEEN ANTIBODIES TO COWDRIA-RUMINANTIUM (RICKETTSIALES)IN CATTLE AND THE DISTRIBUTION OF AMBLYOMMA VECTOR TICKS IN ZIMBABWE

Cowdriosis, caused by Cowdria ruminantium, is transmitted by Amblyomma ticks, which are widely distributed in Zimbabwe. To assess the distri bution of this disease in Zimbabwe, cattle either exposed to Amblyomma ticks or maintained in areas free from these ticks were tested for an tibodies to Cowdria. A total of 324 sera were tested using competitive ELISA and the indirect fluorescent antibody test (IFAT). At diptanks in Amblyomma-infested areas 52% (n=95) and 26% (n=47) of sera were pos itive by cELISA and IFAT, respectively. At diptanks in Amblyomma-free areas 11% (n=125) and 10% (n=134) of sera were positive by cELISA and IFAT, respectively. The results were significantly different between A mblyomma-infested and tick-free areas (X(2) = 24.73, P less than or eq ual to 0.005 for IFAT and X(2) = 57.53, P less than or equal to 0.005 for cELISA). High background readings in field sera, possibly due to c ross-reactive antibodies to Ehrlichia spp., complicated the determinat ion of a realistic cut-off point, especially in cELISA. On the basis o f the distribution of Amblyomma ticks, currently a large part of Zimba bwe can be considered endemic for the disease.