The influence of the size of the initial inoculum on the efficacy of isometamidium (samorin) on a stock of Trypanosoma congolense.

The effect of the number of trypanosomes in the initial inoculum on the minimum curative dose, was determined for an experimental infection of Trypanosoma congolense in mice treated with isometamidium. Mice were infected by the intravenous route and were then treated three hours later by intraperitoneal injection. The minimum curative dose was shown to be dependent on the size of the initial inoculum, with a difference of a factor of 7.5 as the initial inoculum was increased from 10(3) to 10(6) trypanosomes per mouse. It is concluded that this may be a significant variable for in vivo drug sensitivity test, and may also have implications for treatment of infections in the field.