A key for identifying faecal smears to detect domestic infestations of triatomine bugs

Abstract

Early detection of residual populations of domestic triatomine bugs that survive insecticide treatment is a key component of successful evaluation and vigilance for Chagas disease control. We have recently demonstrated that sheets of paper, tacked on to the walls of infested houses, can become streaked with the faeces of triatomine bugs and thus reveal thepresence of an infestation. In thispaper, wepresent a simple key to differentiate the faecal streaks of triatomine bugs from those of other domestic arthropods such as cockroaches, ticks and cimicid bedbugs.

Chagas Disease Vector Control in Tupiza, Southern Bolivia

“…Houses were also to be monitored by providing householders with plastic bags in which to keep any bugs they found, and application of paper sheets on house walls to monitor evidence of bug faecal deposits (Garcia Zapata et al 1985, Schofield et al 1986 although in the event, paper sheets were applied only to 11 houses. Insecticide deposits were also to be monitored by wall surface bioassays in 10 houses using laboratory reared fifth instars of T. infestans.…”

Defecation Behavior and Ecology of Insects

“…Insects that take liquid plant food (e.g., phloem or xylem sap, or nectar) generally produce a liquid waste containing carbohydrates and amino acids, and those that feed on solid plant parts produce green to brown pellets (58, 99). A liquid diet of animal origin (e.g., blood) yields moist feces, dark brown or black in color owing to the presence of undigested heme; a diet of animal tissue produces dark-colored excrement that is often sticky or hard (124). The characteristics of an insect's waste may change over ontogeny as its diet changes.…”

“…Indeed, several authors have produced dichotomous keys and guides designed to permit the identification of a range of insects, including forest leaf-feeders, grasshoppers, blood-sucking bugs, chalk-stream insects, and household product pests, based entirely on fecal characteristics (62, 80,94,124,141). It is even possible to recognize sphingid and beetle feces from 65-millionyear-old fossils (85; P. Herendeen, personal communication).…”

“…Because the texture, shape, size, and sometimes color of fecal materials are often characteristic for a species feeding on a given host, examination of waste products may permit the identification of an insect in its absence (94,124,141).…”

“…Fecal pellet size provides a convenient index of growth for stored-product pests (120), and the characteristic droppings of triatomine bugs allow the detection of low-density domestic infestations of these vectors of Chagas disease (124).…”