title: An in vitro assay for testing mosquito repellents employing a warm body and carbon dioxide as a behavioral activator.
abstract: We describe here an in vitro behavioral assay for testing mosquito repellents applied in a dose-based manner to a warm body (34 degrees C) in test cages. The system was used to assess the sensitivity of 4-6-day-old Anopheles gambiae to the insect repellent diethyl methyl benzamide (deet). These tests were made in the absence and presence of additional carbon dioxide (CO2) applied as a pulse to activate mosquitoes in the cages. In the absence of the CO2 pulse the mosquitoes hardly responded to the warm body. Increasing the CO2 level in the cage by 1,000 parts per million caused a 25-fold increase in the number of landings by mosquitoes on the warm body in 2-min tests. This mosquito activation allowed the measurement of a significant reduction in the number of landings to bite on the warm body with increasing doses of deet (0.4 to 3.8 microg/cm2). An asymptotic nonlinear model fitted to the repellency data in the presence of CO2 allowed estimation of the effective dose of deet that reduced landings to bite by 50% (ED50) at 0.95 microg/cm2 (5 nmol/cm2) and the corresponding ED95 at 4.12 microg/cm2 (21.5 nmol/cm2). This in vitro bioassay has the advantage of permitting a fast throughput of test products under standardized conditions and is suitable for screenings designed for the purpose of discovering lead products with as yet unknown human toxicological and dermatological profiles.
authors.affiliation: Laboratory of Animal Physiology, Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kröber
authors.forename: Sébastien
authors.initials: S
authors.lastname: Kessler
authors.forename: Jérôme
authors.initials: J
authors.lastname: Frei
authors.forename: Martine
authors.initials: M
authors.lastname: Bourquin
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Guerin
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects* / Q000502:physiology*; D001522:Behavior, Animal / Q000187:drug effects; D002245:Carbon Dioxide; D003671:DEET / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006358:Hot Temperature; D007302:Insect Repellents / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D007302:Insect Repellents; D003671:DEET; D002245:Carbon Dioxide