Identification of permethrin and etofenprox cross-tolerance in Rhipicephalus sanguineus sensu lato (Acari: Ixodidae).

BACKGROUND: The brown dog tick, Rhipicephalus sanguineus sensu lato (Latreille; Acari: Ixodidae), is a peridomestic ectoparasite of dogs and occasionally humans. In some populations, lack of integrated pest management practices and overuse of pesticides has resulted in high levels of resistance to multiple active ingredients. In this study, we established the etofenprox discriminating concentration (DC) and three additional screening concentrations to evaluate resistance status. Using mortality results, cross-resistance was investigated in brown dog tick populations from five geographically disparate regions, including Asia, Africa, Europe, North America, and the Caribbean, following exposure to the DC for both etofenprox and permethrin separately. Subsequently, using both larval packet tests and molecular methods, etofenprox resistance was investigated. RESULTS: The etofenprox DC was set at 0.51%, which allows for the rapid screening of peridomestic brown dog tick populations for resistance to this active ingredient. Cross-tolerance to two sodium channel-inhibiting pesticides, permethrin and etofenprox, was observed in one population. CONCLUSION: Our study has provided a single etofenprox concentration that can be used in larval packet tests to determine resistance status in collected peridomestic brown dog ticks, which is particularly important when a single to a few engorged adult ticks are provided for evaluation. Although metabolic resistance is presumed to be the primary resistance mechanism, a sodium channel mutation also confers tolerance to etofenprox at the DC. © 2019 Society of Chemical Industry.

Methionine as a safe and effective novel biorational mosquito larvicide.

BACKGROUND: Mosquito larvicides provide a source-reduction strategy to diminish adult females that bite and potentially spread pathogens. Demands are mounting for new and innovative effective biorational larvicides, due to the development of resistance to some currently utilized mosquito larvicides, undesirable non-target effects, and US Environmental Protection Agency (EPA) restrictions. Methionine is a human nutrient essential amino acid that unexpectedly has been shown to be a valuable safe pest management tool against select insect pests that possess alkaline gut physiology. The present study evaluated larvicidal toxicity of methionine in several pestiferous mosquito (Diptera: Culicidae) genera. RESULTS: Concentration-dependent DL-methionine kinetics assays of survival and pupation were conducted in larvae of Aedes albopictus Skuse, Anopheles quadrimaculatus Say, and Culex tarsalis Coquillett in glass jars. High concentrations of DL-methionine yielded 100% mortality for all test species and prevented pupation at a rate equivalent to Bacillus thuringiensis israelensis (Bti) treatments. Concentration kinetics indicated that An. quadrimaculatus was 10-fold more sensitive to DL-methionine than Ae. albopictus and Cx. tarsalis. CONCLUSIONS: EPA regulations currently exempt methionine in pesticide formulations applied to agricultural crops. This study demonstrates that methionine is a highly effective mosquito larvicide that can provide a beneficial new biorational, environmentally sustainable tool to control pestiferous mosquitoes. © 2018 Society of Chemical Industry.

To bite or not to bite! A questionnaire-based survey assessing why some people are bitten more than others by midges.

BACKGROUND: The Scottish biting midge, Culicoides impunctatus, responsible for more than 90% of biting attacks on human beings in Scotland, is known to demonstrate a preference for certain human hosts over others. METHODS: In this study we used a questionnaire-based survey to assess the association between people's perception of how badly they get bitten by midges and their demographic, lifestyle and health related characteristics. RESULTS: Most people (85.8%) reported being bitten sometimes, often or always with only 14.2% reporting never being bitten by midges when in Scotland. There was no association between level of bites received and age, smoking, diet, exercise, medication, eating strongly flavoured foods or alcohol consumption. However, there was a strong association between the probability of being bitten and increasing height (in men) and BMI (in women). A large proportion of participants (33.8%) reported experiencing a bad/severe reaction to midge bites while 53.1% reported a minor reaction and 13.1% no reaction at all. Also, women tend to react more than men to midge bites. Additionally, the results indicated that the susceptibility to being bitten by midges is hereditary. CONCLUSIONS: This study suggests that midges prefer to bite men that are tall and women that have a large BMI, and that the tendency for a child to be bitten or not could be inherited from their parent. The study is questionnaire-based; therefore, the interpretation of the results may be limited by the subjectivity of the answers given by the respondents. Although the results are relevant only to the Scottish biting midge, the approach used here could be useful for investigating human-insect interactions for other insects, particularly those which transmit pathogens that cause disease.