Abstract
BackgroundIncreasing reports of high-resistant Triatominae populations concerns scientists and sanitarians as little is known about the factors behind the occurrence of such phenotype and its real impact on vector control strategies. Moreover, the utilization of a large variety of methodologies hinder the comparison of the reported studies.MethodsThis work aims to review laboratory bioassays, redefining the assessed biological features (age, generation and insecticide application area) and technical procedures (mortality recording time and the ideal diagnostic dose).ResultsResults were not influenced by the insecticide application area in nymphs or by their generation. Three days-old specimen’s revealed lower susceptibility to the tested insecticide. We determined that it is more appropriate to record mortality 72 h after treatment with insecticide, as well as using a diagnostic dose of 1xDL99.ConclusionThis work suggests more adequate methodological parameters for assessing insecticide resistance in triatomines, which also allows the comparison of results obtained by different research groups. For laboratory bioassays, we recommend: 1) the use of first instar nymphs from first or second generation; 2) 3 day-old specimens; 2) application of insecticide in the dorsal or ventral abdomen area; 3) mortality recording 72 h after treatment with pyrethroids and 4) a diagnostic dose of 1x LD99.
Highlights
Increasing reports of high-resistant Triatominae populations concerns scientists and sanitarians as little is known about the factors behind the occurrence of such phenotype and its real impact on vector control strategies
There is only one protocol guiding the studies of triatomine insecticide resistance, which belongs to the World Health Organization (WHO) [7]
According to the methodology proposed by the WHO [7], studies to assess the susceptibility of triatomines to insecticides in laboratory must be performed with first instar nymphs of the F1 generation (5 to 7 days of age, fasting, weight 1.2 ± 0.2 mg)
Summary
Increasing reports of high-resistant Triatominae populations concerns scientists and sanitarians as little is known about the factors behind the occurrence of such phenotype and its real impact on vector control strategies. Reports of resistant triatomine populations since the last decade have caused great impact among the scientific community, challenging them to find new alternatives for vector control strategies. In this case, insecticide resistance became the priority in the Chagas disease scenario, which requires better characterization and delimitation. The utilization of a large variety of methodologies has been reported [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23], which prevents direct comparison of results and, in a more practical way, the comprehension of the real impact of those results in field vector control strategies. Topical application of insecticide must be in the dorsal of abdomen and the mortality recorded at 72 h after treatment with the active chemical
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