Host-feeding patterns of domiciliary Triatoma infestans (Hemiptera: Reduviidae) in northwest Argentina: seasonal and instar variation

Blood meal sources of 1,964 Triatoma infestans Klug collected in bedrooms in 3 rural villages in northwest Argentina were identified by agar double-diffusion tests. Bugs were collected in September (1988, end of winter), October (1992), December (1988, spring), and March (1989, 1992, summer), and tested for human, dog, cat, chicken-duck, and goat-sheep serum antigens. From late winter to late summer, the percentage of domiciliary T. infestans that fed on humans decreased from 81 to 50-51%, whereas the percentage of bugs that fed on dogs rose from 39 to 45-57%, on chickens from 8 to 41) 54%, and on cats from 7 to 12-23%. Bugs that fed on goat-sheep (2%) were collected mostly from 1 house. In winter, most bugs fed on humans,only (48%), followed by dogs only (13%), cats only, or chickens only (approximately 1%). In spring-summer, the percentages of bugs that fed exclusively on humans (19%), dogs (16%), or chickens (17%) were similar. The seasonal shift was associated closely with changes in the sleeping places of people from indoors in winter to verandahs in summer, and with the presence of brooding hens or ducks in or close to bedrooms in spring-summer. In spring-summer, at each instar, bugs had more identified blood meals, switched hosts from earlier instars, fed on a larger number of different host types, and took mixed meals more frequently than in winter. Bugs collected from walls, roofs and household goods showed similar blood-feeding patterns, whereas bugs from beds showed the highest frequency of human meals. The increased anthropophagy of domiciliary T. infestans populations at the end of winter and during spring precedes or coincides with the spring peak incidence of acute cases of Chagas disease in the region. This is the 1st report documenting seasonal variation in host selection of any triatomine species.