Comparison of indoor searches with whole house demolition collections of the vectors of Chagas disease and their indoor distribution

Abstract

The number of Triatoma dimidiata found per rnan-hour of collection in each of the three mud-walled houses were 4, 1 and 37, In the third house 8 of T nitida were also collected.When the walls of these houses were dismantled, an additional 1 14, !41 and 307 of Tl dimidiata were cellected along with 34 of T nitida in the third house, In the palm-thatch roofed huts only Rhodnius Protixus were collected. The numbers per man-hour collected were 1 1, 27 and 26. When the roofs were dismantled and searched 75, 449 and 978 bugs were found in the respective houses. These results indicate that the numbers collected by the traditional method did not accurately refiect the population density in the houses, The collections indicate that the hiding places of 71 dimidiata and R, Prolixus were very lirnited within the houses, An average of 31% of T dimidinta were collected in only two dismantled block sections (2m2) which were close to the beds and chicken nest and 40% of R. protixus in the last house were obtained in the lower section of the palm-thatched roofs just abeve a bed, This area occupied only 4.2% area in total space of the house, These results suggest that insecticidal treatments would be most effective if they focused on the places where more bugs concentrate.

Geographic distribution and morphometric differentiation of Triatoma nitida usinger 1939 (Hemiptera: Reduviidae: Triatominae) in Guatemala

“…In a previous study (Monroy et al 1998b) we reported the case of one house where T. dimidiata and T. nitida were found together. In this house, T. dimidiata bugs were nine times more abundant and mainly positioned close to beds and chicken nests, while the specimens of T. nitida were dispersed throughout the house, probably compelled to disperse from suitable sites because of the competition with T. dimidiata.…”

“…Following Chagas control programs in Guatemala it is expected a diminution of the intradomestic presence of other triatomines (T. dimidiata, R. prolixus), the possibility exists in some areas that T. nitida could invade and colonize the empty microhabitats, based on our previous observation of competition with T. dimidiata (Monroy et al 1998b). We recommend on-going vigilance, especially in the department of Quiche, where the intradomestic colonization of T. dimidiata is not very high and more abundant in the peridomicile; also, the entomological surveys by the Ministry of Health in this department are showing that T. nitida is very common inside and outside the houses (Mr Guillermo Hernández, pers.…”

Effectiveness of Large-Scale Chagas Disease Vector Control Program in Nicaragua by Residual Insecticide Spraying Against Triatoma dimidiata

“…Monroy and others compared the number of T. dimidiata found by the man-hour search method with that found after demolishing an entire house and showed that only 7.0% of the total bugs present could be found by the man-hour method. 24 This manual searching technique involves technical bias owing to inspectors' motivation and skill. It is possible that in our study, those bug inspectors who performed the first entomological evaluation had improved their bug searching skills by the second evaluation.…”

“…Bedrooms and sleeping areas were prioritized for spraying because T. dimidiata bugs are often found around beds. 24 Kitchens were not sprayed, to avoid contamination of stored food or water with insecticide. In particular, larger amounts of insecticide were deposited within cracks in walls, if present, for improved effectiveness against T. dimidiata hidden inside the cracks.…”

Chagas Disease: Assessing the Existence of a Threshold for Bug Infestation Rate

“…In fact, a previous study in Guatemala reported that the method detected only 7% (= 42 of 604) of the total number of T. dimidiata bugs collected through demolition of mud walls. 22 Needless to say, counting the number of the bugs through demolition of mud walls provides the most accurate infestation rate. Yet, it is absolutely unrealistic to demolish mud walls of every target housing structure inhabitants currently live in, for both an economic reason (i.e., financial and temporal resource limitations in inclusion of replacement wall rebuilding in the routine surveillance activity components) and a cultural reason (i.e., potential emotional attachment to mud wall at specific households).…”