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Chagas disease is an infectious disease of human and animal health concern, with 6–8 million chronic human infections and over 50,000 deaths throughout the Americas annually. Hematophagous insects of the subfamily Triatominae, also called kissing bugs, vector the protozoan parasite, Trypanosoma cruzi Chagas (Trypanosomatida: Trypanosomatidae), that causes Chagas disease. Despite the large human health burden, Chagas disease is a neglected tropical disease with inadequate funding for research and preventive practices. Given the resource-poor environment of most agencies trying to protect public health, it is critical to consider all control options for reducing vector populations and the risk of human exposure to T. cruzi to identify the most appropriate tools for each context. While numerous triatomine control methods exist, the literature lacks a compilation of the strategies used, a critical examination of their efficiency, and a particular focus on triatomine control in the United States compared to elsewhere in the Americas. Here, we present a review of the literature to assess historical intervention strategies of existing and developing triatomine control methods. For each method, we discuss progress in the field, future research to further advance the method, and limitations. While we found that pyrethroid insecticide is still the most commonly used method of triatomine and Chagas disease control, we suggest that complementing these techniques with alternative control methods in development will help to achieve Chagas disease reduction goals.

Background Residual spraying with pyrethroid insecticides is still the main strategy used to prevent vector-borne transmission of Trypanosoma cruzi , the etiological agent of Chagas disease. The emergence of resistance to these insecticides in triatomine populations associated with vector control failure highlights the need to evaluate alternative tools, such as xenointoxication. Chickens serve as important blood meal sources and are positively associated with triatomine abundance. Therefore, several endectocides have been tested in chickens, with fluralaner exhibiting the best results. However, the effect of treating chickens with fluralaner has not been evaluated in pyrethroid-resistant triatomines. Here, we aimed to assess the efficacy and duration of the lethal effect of fluralaner on pyrethroid-resistant and susceptible Triatoma infestans using chickens as treated hosts under semi-experimental conditions with a treated–control design. Methods Three chickens received two oral doses of Bravecto ® (fluralaner, MSD Animal Health) at 0.5 mg/kg, whereas three other chickens were assigned to the control group, which received only semolina. Third- to fifth-instar nymphs, both susceptible and resistant to pyrethroid insecticides, were exposed to the chickens at five specific times: 0 (pre-treatment), 3, 7, 14, and 28 days post-treatment (DPT). We recorded the degree of triatomine engorgement and assessed feeding success and survival after each exposure. The data were analyzed via logistic regressions and Kaplan‒Meier curves. Results Feeding success rates were high, ranging from 95.5% to 100% throughout the trial, and were not affected by treatment or exposure time. The greatest lethal effects of fluralaner on triatomines exposed to treated chickens were observed up to 14 DPT, with cumulative mortality ranging from 76.9% to 87.0%. At 28 DPT, triatomine mortality decreased significantly to 12.8%, similar to the control group means (< 17.9%) and pre-treatment levels (6.8%). No difference in the lethality of fluralaner was detected between susceptible and pyrethroid-resistant triatomines via logistic regression analysis. Conclusions On the basis of these and previous results, chickens are eligible for a field study that addresses the efficacy of simultaneous xenointoxication of various hosts using fluralaner. This approach provides a promising alternative for addressing the challenge of resistance to pyrethroid insecticides in triatomines. Graphical Abstract

Background Chagas disease remains a persistent vector-borne neglected tropical disease throughout the Americas and threatens both human and animal health. Diverse control methods have been used to target triatomine vector populations, with household insecticides being the most common. As an alternative to environmental sprays, host-targeted systemic insecticides (or endectocides) allow for application of chemicals to vertebrate hosts, resulting in toxic blood meals for arthropods (xenointoxication). In this study, we evaluated three systemic insecticide products for their ability to kill triatomines. Methods Chickens were fed the insecticides orally, following which triatomines were allowed to feed on the treated chickens. The insecticide products tested included: Safe-Guard® Aquasol (fenbendazole), Ivomec® Pour-On (ivermectin) and Bravecto® (fluralaner). Triatoma gerstaeckeri nymphs were allowed to feed on insecticide-live birds at 0, 3, 7, 14, 28 and 56 days post-treatment. The survival and feeding status of the T. gerstaeckeri insects were recorded and analyzed using Kaplan–Meier curves and logistic regression. Results Feeding on fluralaner-treated chickens resulted 50–100% mortality in T. gerstaeckeri over the first 14 days post-treatment but not later; in contrast, all insects that fed on fenbendazole- and ivermectin-treated chickens survived. Liquid chromatography tandem mass spectrometry (LC-QQQ) analysis, used to detect the concentration of fluralaner and fenbendazole in chicken plasma, revealed the presence of fluralaner in plasma at 3, 7, and 14 days post-treatment but not later, with the highest concentrations found at 3 and 7 days post-treatment. However, fenbendazole concentration was below the limit of detection at all time points. Conclusions Xenointoxication using fluralaner in poultry is a potential new tool for integrated vector control to reduce risk of Chagas disease. Graphical Abstract