Evaluation of a short-term in vitro growth-inhibition test to determine susceptibility of Trypanosoma vivax stocks to various trypanocides.

Two Trypanosoma vivax stocks were initiated in culture with tsetse or culture-derived metacyclics. They were propagated axenically as bloodstream trypomastigotes at 35 degrees C in 4% CO2 in air. Populations of trypanosomes were incubated with various concentrations of antitrypanosomal compounds, namely diminazene aceturate, quinapyramine sulphate, DL-alpha-difluoromethylornithine, isometamidium chloride, suramin and melCy. Growth was monitored after 24 h of incubation and the growth inhibition was calculated. All six drugs tested showed little effect upon the growth of the parasite populations. These results indicate that a 24-h growth-inhibition test was not suitable for determining the drug susceptibility of T. vivax stocks in vitro. Neither did the results correlate with those obtained with susceptible or resistant stocks of T.b. brucei, T.b. evansi or T. simiae described in the literature, or with the results of these two T. vivax stocks tested in cattle.