Development of metacyclic forms of Trypanosoma brucei sspp. in cultures containing explants of Phormia regina Meigen.

When procyclic trypanosomes of Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense were cultivated in Nunclon 25 cm2 flasks at 27 C in a liquid medium containing various tissue explants of Phormia regina Meigen, some of them developed into forms infective for mice. The infective stages were present at various periods of up to 29 days when the cultures were terminated. Larger numbers of explants of head-salivary glands than the other tissues used were required to produce infections. Infectivity titrations on trypanosome suspensions of T. b. brucei TRUM 252 and T. b. rhodesiense TRUM 497 indicated that only a small proportion of the populations was infective. Mice were rarely infected with trypanosomes grown in medium without explants. Only 1 mouse of the 11 inoculated developed a parasitemia from a control culture of T. b. rhodesiense TRUM 545. A few trypanosomes resembling epimastigotes and metacyclic forms were seen in stained samples of infective inocula.