The pathogenicity of diminazene aceturate-resistant Trypanosoma brucei in rats after treatment with the drug.

Four groups (A, B, C and D) of 10 rats were used to determine the effect of comparatively high doses of diminazene aceturate on diminazene aceturate-resistant Trypanosoma brucei and the pathogenic effect of relapse infection. Group A rats were uninfected (controls) while group B, C and D rats were inoculated intraperitoneally with 0.5 x 10 (6) diminazene aceturate-resistant T. brucei and treated with diminazene aceturate at 14.0, 17.5 and 21.0mg/kg body weight, respectively, on day 14 post-infection (PI) as a single intraperitoneal injection. Prepatent periods and also levels of parasitaemia were comparable in groups B, C and D. Packed cell volume (PCV) decreased in the infected groups by day 14 PI and returned to pre-infection values by day 63 post-treatment (PT). Anaemia was comparable in groups B, C and D. Relapse parasitaemia occurred in six rats in group B on day 70 PT and in five rats in each of groups C and D on day 77 PT. The PCV of the rats with relapse infection decreased progressively up to day 105 PT, when the experiment was terminated, whereas the PCV of rats without relapse did not. The levels of anaemia and parasitaemia on day 14 post-relapse were significantly higher (P<0.05) than the levels obtained on day 14 PI in the same animals. Thus, comparatively high doses of diminazene aceturate failed to cure drug-resistant T. brucei infection in 50-60% of infected rats and relapse infections were more severe than the primary infections before treatment.