HEARTWATER IN GHANA - IMPLICATIONS FOR CONTROL OF TICKS

Heartwater, an often fatal rickettsial disease of domestic ruminants t ransmitted by Amblyomma variegatum ticks, ranks with the A. variegatum -associated skin disease dermatophilosis as a major constraint to the upgrading of livestock productivity in Ghana. An epidemiological surve y, using new diagnostic tests, is being carried out to determine the i ncidence and distribution of hear water and other tick-borne diseases in Ghanaian cattle, sheep and goats. Preliminary results from a longit udinal survey being carried out at sites in the Greater Accra Region i ndicating that although the vector ticks and the disease agent are wid espread outside urban areas, not all animals are being exposed to hear twater during the first few months of life when an inverse age related resistance allows development of immunity without clinical disease. T hus a susceptible sub-population, at risk from heartwater, can exist e ven in areas of high tick challenge. The significance of these results for present and future tick and disease control strategies is discuss ed.