EFFECT ON HERD HEALTH AND PRODUCTIVITY OF CONTROLLING TSETSE AND TRYPANOSOMOSIS BY APPLYING DELTAMETHRIN TO CATTLE

A large cattle ranch was established in 1954 in a heavily tsetse infes ted part of north-east Tanzania. Trypanosomosis was controlled for 30 years by prophylactic drugs but in 1988 drug resistance seemed to be d eveloping as cases of trypanosomosis were being confirmed 4 or 5 weeks after treatment with isometamidium chloride (Samorin). Herd health ha d deteriorated and productivity was uneconomically low. In order to co ntrol the tsetse population the 8,000 cattle, grazing over 250 km2, we re regularly dipped in the synthetic pyrethroid deltamethrin (Decatix Cattle Dip and Spray formulation). Within a year the tsetse population , as monitored by traps, had decreased by more than 90%. Disease morta lity decreased by 66% and a range of productivity measures such as cal ving percentages and weaning weights were raised to levels above those prevailing before the decline in herd health.