Project description:We found that assassin bugs from the earliest-diverging subfamily of higher Reduviidae (Peiratinae), as well as a subfamily closely related to Triatominae (Stenopodainae) have venom that is highly similar in composition to that produced by previously examined reduviids from Harpactorinae and Reduviinae. This finding suggests that venom composition has been largely stable due to purifying selection among the higher Reduviidae, which is consistent with the ancient origin of venom in the ancestors of Heteroptera 250–300 million years ago (Sunagar and Moran 2015; Walker et al. 2018a). This near homogeneity of venom composition is perhaps surprising considering that reduviid predators have evolved numerous instances of prey specialization and specialized hunting strategies that might be expected to co-evolve with venom. Possibly, further studies focussing on species with more specialized hunting strategies, or different kinds of venom bioactivities, will uncover more nuanced venom adaptations. Alternatively, it is possible that the protease-rich venoms of predatory reduviids are simply well-suited to myriad different hunting strategies. These data are consistent with other examples where venoms are surprisingly similar despite great differences in biology, for example between solitary and eusocial bees. A more detailed picture of venom evolution in Reduviidae would examine venom produced by the early-diverging Phymatine complex as well as venoms of non-reduviid cimicomorphs, prey specialists such as the arachnophagous Emesinae and the myrmecophagous Holoptilinae, and some of the many groups that employ hunting specializations, such as the use of plant resins to catch prey (Hwang and Weirauch 2012). Within Triatominae, examination of saliva produced by additional species from multiple lineages (especially those that switched to blood-feeding independently, if the subfamily is shown to be polyphyletic) and including generalists and specialists on different host taxa and species associated especially with nests and burrows will be informative. The venoms of predatory reduviids such as Zelurus spp. and Opisthacidius spp. that are most closely related to Triatominae, and share some behaviours such as habitation of bird nests by Opisthacidius spp. may also provide more information about the evolution of triatomine saliva.

Project description:BACKGROUND: Chagas disease prevention critically depends on keeping houses free of triatomine vectors. Insecticide spraying is very effective, but re-infestation of treated dwellings is commonplace. Early detection-elimination of re-infestation foci is key to long-term control; however, all available vector-detection methods have low sensitivity. Chemically-baited traps are widely used in vector and pest control-surveillance systems; here, we test this approach for Triatoma spp. detection under field conditions in the Gran Chaco. METHODOLOGY/PRINCIPAL FINDINGS: Using a repeated-sampling approach and logistic models that explicitly take detection failures into account, we simultaneously estimate vector occurrence and detection probabilities. We then model detection probabilities (conditioned on vector occurrence) as a function of trapping system to measure the effect of chemical baits. We find a positive effect of baits after three (odds ratio [OR] 5.10; 95% confidence interval [CI(95)] 2.59-10.04) and six months (OR 2.20, CI(95) 1.04-4.65). Detection probabilities are estimated at p ? 0.40-0.50 for baited and at just p ? 0.15 for control traps. Bait effect is very strong on T. infestans (three-month assessment: OR 12.30, CI(95) 4.44-34.10; p ? 0.64), whereas T. sordida is captured with similar frequency in baited and unbaited traps. CONCLUSIONS/SIGNIFICANCE: Chemically-baited traps hold promise for T. infestans surveillance; the sensitivity of the system at detecting small re-infestation foci rises from 12.5% to 63.6% when traps are baited with semiochemicals. Accounting for imperfect detection, infestation is estimated at 26% (CI(95) 16-40) after three and 20% (CI(95) 11-34) after six months. In the same assessments, traps detected infestation in 14% and 8.5% of dwellings, whereas timed manual searches (the standard approach) did so in just 1.4% of dwellings only in the first survey. Since infestation rates are the main indicator used for decision-making in control programs, the approach we present may help improve T. infestans surveillance and control program management.

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Triatoma infestans

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