Biological parameters of Triatoma brasiliensis and T. pseudomaculata that could influence the epidemiological importance of these insects as vectors ofTriatoma brasiliensis Neiva, 1911 and T. pseudomaculata Corrêa & Espínola, 1964 are the most important vectors of Trypanosoma cruzicausative agent of Chagas disease -in the arid caatinga region of Northeastern Brazil. Both species occupy a range of domestic, peridomestic, and sylvatic ecotopes, with T. brasiliensis often associated with small rodents amongst rocky outcrops, and T. pseudomaculata more usually associated with birdnests and hollow trees (Forattini et al. 1981). Application of residual insecticides can eliminate domestic colonies of both species, but houses can then be reinvaded from the silvatic and peridomestic habitats. Our aim in this study, was to compare the two species in terms of various factors that could influence their epidemiological importance as domestic vectors of T. cruzi. MATERIALS AND METHODSSpecimens of T. brasiliensis were collected from peridomestic habitats in the municipality of Simplício Mendes, State of Piauí, and specimens of T. pseudomaculata were similarly collected in the municipality of Crateús, State of Ceará, Brazil. Eggs from the collected adults (40 from T. brasiliensis, 33 from T. pseudomaculata) were placed individually in small pots and observed daily until eclosion. The resulting nymphs were offered a daily feed on an anaesthetized mouse. Those that started feeding were allowed to engorge; those that did not start to feed within 30 min were left until the following day. Once bugs had taken a first blood meal, they were then offered a weekly feed. This regime (maintained at 24 ± 2ºC; 56 ± 6% rh) allowed us to establish the incubation period, the interval between hatching or moulting and the first feeding, the number of blood meals required by each instar, the development time, the net reproductive rate (Ro) and the instantaneous daily reproductive rate (r). In the case of 4th and 5th instar nymphs and adults, we also noted the time-lapse before starting feeding, the duration of feeding and timing of defecation.To determine bloodmeal intake, we used 30 bugs of each instar, weighed before and immediately after feeding. The blood meal intake ratios were calculated in relation to the body weight of each insect using the formula (R = (Wf -Wi)/Wi), where Wf is the weight after feeding (mg) and Wi is the weight before feeding. Blood ingestion velocity was calculated by the formula (V = Wb/T), where Wb is the ingested blood weight (mg) and T is the interval time (minutes) between the beginning and the end of the feeding process.
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