In vitro cultivation of Trypanosoma congolense: establishment of infective mammalian forms in continuous culture after isolation from the blood of infected mice.

Bloodstream form trypomastigotes of four cloned stocks of Trypanosoma congolense from West Africa were successfully adapted to continuous in vitro culture at 28 degrees C using bovine aorta endothelial cell monolayers and Eagle's minimum essential medium supplemented with 20% normal bovine serum or foetal calf serum. The trypanosomes maintained in vitro morphologically resembled bloodstream forms and remained infective for vertebrate hosts. They also induced local skin reactions in rabbits and were therefore designated "mammalian forms", possibly resembling parasites which develop extravascularly in the vertebrate host following introduction of metacyclic trypanosomes into the skin by bites of tsetse flies. Mammalian forms of two stocks were allowed to transform to procyclic trypanosomes in order to obtain cultures producing epimastigote and metacyclic stages of T. congolense. Metacyclic trypanosomes produced in this manner were shown to be neutralized by antiserum raised in rabbits against the homologous trypanosome stock transmitted by tsetse flies.