Infectivity reacquisition by Trypanosoma brucei brucei cultivated with tsetse salivary glands.

Reacquisition of infectivity four mice was observed in cultures of Trypanosoma brucei brucei grown in the presence of tests fly salivary gland explants in a medium based on the amino acid composition of Glossina hemolymph and containing fetal bovine serum. High infection rates were obtained in mice inoculated with about 1.5 X 10(8) organisms. Infectivity reacquisition was correlated with invasion of the salivary glands by the parasites. Few small trypanosomes with subterminal kinetoplasts (metacyclic-like forms) were found in the infective inoculums. The parasitemias in mice consisted of pleomorphic cultivable trypanosomes. Cultures initiated by these organisms and then placed with the head-salivary gland preparations became infective for mice.