Fluralaner systemic treatment of chickens results in mortality in Triatoma gerstaeckeri, vector of the agent of Chagas disease

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

Insecticidal activity of fluralaner (Exzolt®) administered to Gallus gallus domesticus against triatomines (Hemiptera, Reduviidae, Triatominae)

“…Treatment of chickens with a single dose or two doses of fluralaner did not affect the feeding success and engorgement level of the triatomines compared with those that fed on untreated control chickens. Durden et al [ 38 ] showed that treatment of chickens with fluralaner (Bravecto ® ) did not affect feeding success or engorgement level of Triatoma gerstaeckeri . Several studies have demonstrated that some insecticides, such as pyrethroids, have repellent effects against sand flies [ 40 – 42 ].…”

“…Triatomine mortality was observed up to 28 days after treating the chickens. A recent study [ 38 ] demonstrated that treating chickens with two doses of fluralaner (Bravecto ® ), a specific formulation for dogs, resulted in 100%, 90% and 50% mortality of T. gerstaeckeri at days 3, 7 and 14 after a blood meal, respectively. No mortality of T. gerstaeckeri was observed 28 and 56 days after treating the birds [ 38 ].…”

“…A recent study [ 38 ] demonstrated that treating chickens with two doses of fluralaner (Bravecto ® ), a specific formulation for dogs, resulted in 100%, 90% and 50% mortality of T. gerstaeckeri at days 3, 7 and 14 after a blood meal, respectively. No mortality of T. gerstaeckeri was observed 28 and 56 days after treating the birds [ 38 ]. The higher insecticidal activity observed against R. prolixus, T. infestans, T. brasiliensis and T. pseudomaculata compared to that reported in the literature for T. gerstaeckeri might be explained by intrinsic resistance of the triatomine species to fluralaner and the drug formulation used.…”

“…It is worth noting that treatment of chickens with fluralaner (Bravecto ® ) may be less effective than their treatment with fluralaner (Exzolt ® ). Pharmacokinetic studies in chickens have demonstrated that the oral administration of two doses of 0.5 mg/kg fluralaner (Bravecto ® ) and fluralaner (Exzolt ® ) provides detectable levels of fluralaner in plasma for up to 14 and 21 days, respectively [ 38 , 45 , 46 ]. In vivo, fluralaner binds to plasma proteins and can accumulate in cells such as adipocytes, and in the skin, potentially prolonging its insecticidal activity [ 46 , 47 ].…”

“…The administration of fluralaner (Bravecto ® ) to dogs generates insecticidal activity against triatomines such as T. infestans [ 34 , 35 ], T. brasiliensis [ 36 ] and R. prolixus [ 37 ]. A recent study demonstrated that administering fluralaner (Bravecto ® , formulation for dogs) to chickens resulted in insecticidal activity against triatomine bugs [ Triatoma gerstaeckeri (Stal, 1859)] for up to 15 days after treatment [ 38 ]. Hence, the objective of this study was to assess the insecticidal activity of fluralaner (Exzolt ® ) administered to chickens against triatomines ( R. prolixus , T. brasiliensis , T. infestans and T. pseudomaculata ) that are epidemiologically significant in the transmission of T. cruzi to humans in Latin America, an area endemic for Chagas disease.…”