Alternative transmission modes for Trypanosoma cruzi
Abstract
The parasite Trypanosoma cruzi, which causes Chagas’ disease, is
typically transmitted through a cycle in which vectors become infected through
bloodmeals on infected hosts and then infect other hosts through defecation
at the sites of subsequent feedings. The vectors native to the southeastern
United States, however, are inefficient at transmitting T. cruzi in this way,
which suggests that alternative transmission modes may be responsible for
maintaining the established sylvatic infection cycle. Vertical and oral transmission
of sylvatic hosts, as well as differential behavior of infected vectors,
have been observed anecdotally. This study develops a model which accounts
for these alternative modes of transmission, and applies it to transmission between
raccoons and the vector Triatoma sanguisuga. Analysis of the system
of nonlinear differential equations focuses on endemic prevalence levels and on
the infection’s basic reproductive number, whose form may account for how a
combination of traditionally secondary infection routes can maintain the transmission
cycle when the usual primary route becomes ineffective.