Fate of Trypanosoma cruzi, the causative agent of Chagas disease, in bed bugs after oral ingestion or intrathoracic injection

The parasite Trypanosoma cruzi, transmitted by kissing bugs, causes Chagas disease in millions of people in Central and South America. Here we studied potential transmission of T. cruzi by common bed bugs, Cimex lectularius. Trypanosoma cruzi populations in bed bugs were monitored after oral ingestion or intrathoracic injection, with parasite presence in tissues and excreta analyzed microscopically. Natural feeding and defecation behaviors were also observed. After bed bugs ingested T. cruzi-infected blood, the T. cruzi population in their anterior midgut steadily declined during days 1-7 but increased in their posterior midgut/hindgut and in their feces during days 4-7 and 7-10, respectively. No live or dead T. cruzi were observed in the bed bugs' proboscis, salivary glands, and hemolymph, suggesting they did not breach the midgut. When bed bugs were injected intrathoracically with T. cruzi at a low concentration (103 parasites/mL), no parasites were found in the hemocoel, but some were found up to one week after injection with a higher concentration (106 parasites/mL). As T. cruzi was absent from the salivary glands of bed bugs, oral transmission during feeding is highly unlikely. As bed bugs did not defecate while feeding and invariably defecated away from their feeding site, transmission of T. cruzi via bed bug feces - in a mode similar to kissing bugs - is also unlikely. Human consumption of food contaminated with infected bed bugs is a possible, but untested, mode of transmission.