The detection of infestations of Triatominae in houses in regions endemic for Chagas's disease is a criterion frequently used in the selection of areas, or of individual houses, for treatment in insecticide campaigns as well as in the evaluation of insecticide performance. Several different methods for detecting domestic infestations with Triatominae were compared: night capture, capture of five bugs with the aid of a flushing-out agent and use of card boxes of the Gómez-Núñez type. The flushing-out and Gómez-Núñez box methods were found to be equally sensitive, although each failed to detect some infestations which the other detected. The night capture method was slightly more sensitive but was found to be impractical for insecticide trials. Improvement to the flushing-out method, notably the introduction of a systematic search technique, made it much more sensitive than the Gómez-Núñez box method for heavily infested houses and for houses three months after insecticide treatment. Although the sensitivity of the Gómez-Núñez box method increases when the boxes are left in place for a long time, this also limits the value of the information obtained regarding the evaluation of insecticides. On the basis of the results presented, the flushing-out method using a systematic search of the house was found to be the most suitable sampling technique, but it is recognized that this method still has limitations.
Bendiocarb 80WP, applied at 1 and 2 g/m 2 , was compared with BHC 30WP, applied at 0.5 g/m 2 of gamma isomer, for the control of the important Chagas' disease vector Triatoma infestans, in Brazil. The insecticides performance was evaluated in groups of about 20 heavily infested, mud-or adobe-walled houses selected on the basis of pre-spray sample data. These houses, together with a check group of untreated, infested houses, were sampled for the presence of T. infestans pre-spray and at 1, 3, 5, 7 and 9 months post-treatment employing a systematic search technique with the aid of a flushing-out agent. This method was found to detect infestations in from 71 to 95% of the samples taken in groups of infested, untreated houses. Treatment with bendiocarb 80WP at 2 g/m 2 resulted in the elimination of T. infestans from 40 to 50% of the infested houses, whereas BHC 30WP at 0.5 g/m 2 reduced the number of infested houses by 70-80%. In the houses where the bugs were not eliminated the populations were markedly reduced in size by the insecticides, but became reestablished by 5 months post-spraying. Detailed analysis of the field trial sample data together with the results of a simple laboratory experiment suggest that although bendiocarb WP powder may be intrinsically more toxic to triatomines than BHC WP, it is less persistent when applied in houses largely constructed of mud.
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