FIELD-EVALUATION OF THE PROPHYLACTIC EFFECT OF AN ISOMETAMIDIUM SUSTAINED-RELEASE DEVICE AGAINST TRYPANOSOMIASIS IN CATTLE

In order to compare the prophylactic effect provided by a poly(D,L-lac tide) sustained-release device (SRD) containing isometamidium (ISMM) w ith that provided by the classical intramuscular injection of the drug , a field trial was carried out at the Madina Diassa Ranch in Mall. On e-to 3-year-old N'Dama cattle were randomly divided into three groups. The first group (n = 42) was treated with ISMM at a dose of 1 mg/kg o f body weight, the second group (n = 44) received the same dose of the drug via an SRD, which was subcutaneously implanted in the shoulder r egion, and the third group (n = 36) was kept as an untreated control g roup. All animals were treated with diminazene aceturate (7 mg/kg of b ody weight) 2 weeks before the start of the experiment and were tested monthly by the huffy coat technique for a period of 8 months. Glossin a morsitans submorsitans was the most important tsetse species, with a pparent densities (number of catches/trap/day) varying between 11.9 an d 38.7 over the experimental period. Eight months after treatment the cumulative infection rates were 27.7, 58.5, and 77.4% in the group wit h the SRD implant, the group receiving the intramuscular injection, an d the control group, respectively. Statistical analysis showed that th e incidence of trypanosomiasis was significantly lower (P = 0.006) in the group which received ISMM via the SRD than in the one which was tr eated with ISMM intramuscularly.