In vitro cultivation of Trypanosoma congolense: the production of infective forms from metacyclic trypanosomes cultured on bovine endothelial cell monolayers.

After transfer to bovine endothelial cell monolayers cultured in Eagle's minimal essential medium at 28 degrees C or 37 degrees C metacyclic trypanosomes of three cloned stocks of Trypanosoma congolense became morphologically similar to parasites found in the bloodstream of the vertebrate host. The trypanosomes resumed division and grew in close association with the mammalian cells, which were essential for growth. These dividing infective forms had the ability to cause local skin reactions and systemic infections when inoculated intradermally into rabbits. Trypanosomes grown in medium supplemented with foetal calf serum (FCS) eventually differentiated into procyclic forms. No such change occurred in medium supplemented with normal bovine serum. If procyclic forms in FCS were allowed to continue their differentiation at 28 degrees C they eventually produced epimastigotes which gave rise to infective metacyclic trypanosomes once more. It was thus possible to grow and maintain several different developmental stages of T. congolense by varying culture conditions.