Inheritance of susceptibility to Trypanosoma cruzi infection in Rhodnius prolixus

MILLIONS of cases of Chagas' disease exist in Central and South America 1 . Apart from being virtually incurable, a major problem in this disease is symptomless carriers harbour trypanosomes all their lives but it is often difficult to demonstrate the parasite 2 . At present, the simplest and most sensitive method of diagnosis 3 is to feed uninfected triatomine bugs on the suspected case and subsequently to examine a faecal sample from the bug for the presence of trypanosomes. There is, however, great variation both within and between species of Triatominae, in their susceptibility to infection with Trypanosoma cruzi (see, for example, refs 4 and 5), and though a genetic basis for this variation in susceptibility has been suggested 4 , it has not been verified. Obviously, the production of a highly susceptible strain of triatomine bug that would provide a quick and accurate diagnosis of chronic Chagas' disease would be a distinct advantage. I report here on the selection of both susceptible and refractory lines of Rhodnius prolixus , and the results of this selection programme are related to the genetic control of susceptibility to infection with T. cruzi .