Pleomorphism in trypomastigotes of Trypanosoma cruzi from blood and cell culture.

The sequential variation in the body type of trypomastigotes of the 'Brazil' strain of Trypanosoma cruzi was followed in 4 experimental models: Cultures of Vero fibroblasts incubated at 37 degrees C. Cultures of fish epithelial cells (Pimephales promelas) incubated at 37 degrees C. Blood of C3H mice inoculated with trypomastigotes from 37 degrees C Vero cell culture. Blood of C3H mice inoculated with trypomastigotes from blood of CF1 mice. In both animal models, the picture was similar: a great preponderance of the slender forms in the first days post-infection, followed by a rapid decline while the broad forms reached a peak level; the broad forms in turn declined in the final days, while the stout forms rose sharply in relative number. In the cell culture models, the same tendencies were visible, though less strongly marked. The possible biological and epidemiological significance of this constant pattern of pleomorphism is discussed.