Studies of the persistence of infectivity of Trypanosoma cruzi. III. Effect of human sweat.

Experiments designed to investigate the suggestion that human sweat has a trypanocidal effect did not support this hypothesis under the test conditions described. These studies are designed to investigate factors influencing the chance of infection of man when metacyclic trypanosomes in bug faeces are deposited on the human skin. As mentioned in the first paper in this series (Alvarenga & Marsden) we have epidemiological evidence that people can live for years in houses with infected bugs and not acquire the disease although skin contamination with infected faeces must occur frequently. Wood showed that metacyclic trypanosomes of T. cruzi lost their motility within 30 minutes after exposure to human sweat. He did not report infectivity experiments. Since such an effect would limit the chances of T. cruzi transmission under field conditions we decided to repeat Wood's experiments with observations on the infectivity of trypanosome suspensions.