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Host seeking by the malaria mosquito Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) is mainly guided by volatile chemicals present in human odours. The skin microbiota plays an important role in the production of these volatiles, and skin bacteria grown on agar plates attract An. gambiae s.s. in the laboratory. In this study, the attractiveness of volatiles produced by human skin bacteria to An. gambiae s.s. was tested in laboratory, semi-field, and field experiments to assess these effects in increasing environmental complexity. A synthetic blend of 10 compounds identified in the headspace of skin bacteria was also tested for its attractiveness. Carbon dioxide significantly increased mosquito catches of traps baited with microbial volatiles in the semi-field experiments and was therefore added to the field traps. Traps baited with skin bacteria caught significantly more An. gambiae s.s. than control traps, both in the laboratory and semi-field experiments. Traps baited with the synthetic blend caught more mosquitoes than control traps in the laboratory experiments, but not in the semi-field experiments. Although bacterial volatiles increased mosquito catches in the field study, trapping several mosquito vector species, these effects were not significant for An. gambiae s.l. It is concluded that volatiles from skin bacteria affect mosquito behaviour under laboratory and semi-field conditions and, after fine tuning, have the potential to be developed as odour baits for mosquitoes.

Females of the African malaria vector, Anopheles gambiae Giles sensu stricto, use human volatiles to find their blood-host. Previous work has shown that ammonia, lactic acid, and aliphatic carboxylic acids significantly affect host orientation and attraction of this species, In the current study, these compounds were tested for their attractiveness relative to human emanations in vivo and in vitro. Emanations from a human hand, incubated sweat, and foot skin residues on a nylon sock were significantly attractive when tested against clean air. In a dual-choice test, foot skin residues were significantly more attractive than emanations from a human hand in vivo. Ammonia alone attracted more mosquitoes than fresh or incubated sweat, However, the odor of a human hand or of foot skin residues were more attractive than ammonia. A known attractive blend of ammonia with lactic acid and carboxylic acids was less effective than natural foot odorants, The results demonstrate that the synthetic blend based on skin odor is attractive for An. gambiae, but that in a choice situation in vitro natural skin odors are still preferred by the mosquito. Differences in volatile organic compound abundances between a worn sock and the synthetic blend may have resulted in stronger attraction to the sock. This suggests that candidate attractants should be evaluated with consideration of the strength of natural odorant sources, The data furthermore suggest that additional unidentified compounds from the human foot are involved in the host-seeking behavior of this mosquito species.

Microbiota on the human skin plays a major role in body odour production. The human microbial and chemical signature displays a qualitative and quantitative correlation. Genes may influence the chemical signature by shaping the composition of the microbiota. Recent studies on human skin microbiota, using 16S rRNA gene sequencing, found a high inter- and intrapersonal variation in bacterial species on the human skin, which is relatively stable over time. Human body odours mediate the attraction of mosquitoes to their blood hosts. Odours produced by skin microbiota are attractive to mosquitoes as shown by in vitro studies, and variation in bacterial species on the human skin may explain the variation in mosquito attraction between humans. Detailed knowledge of the ecology and genetics of human skin microbiota is needed in order to unravel the evolutionary mechanisms that underlie the interactions between mosquitoes and their hosts.

Met het de bevindingen uit het laboratoriumonderzoek van Jetske de Boer en Marcel Dicke (Entomologische berichten; Jrg. 64 no. 4(2005)) als leidraad, worden de meningen van twee collega's uit de praktijk, over fundamenteel onderzoek en de relevantie voor de praktijk, in dit artikel beschreven

A coupled gas-chromatography-electroantennography (GC-EAG) method was used to identify kairomones that mediate the host-seeking behaviour of An. gambiae. Nylon stockings that had been worn by human volunteers were found to be highly attractive to female An. gambiae in olfactometer experiments. Tenax-trapped headspace of 15 pairs of stockings and extracts thereof were analysed with GC-EAG. EAG responses were detected repeatedly at 23 retention times, and 14 compounds were identified that elicited on-line EAG responses. The role of these compounds as kairomones in the host-seeking behaviour of An. gambiae is discussed.

Despite its long association with man, the housefly (Musea domestica Linnaeus) remains one of the most difficult pests to control. It is a ubiquitous insect that can be found in houses, stables, food processing factories and other domesticated areas and buildings. Reliance on insecticides for fly control is decreasing because of increased environmental constraints and insecticide resistance. So far, biological control with natural enemies often has disappointing results. Light- and odour-baited traps are considered to be promising devices to control houseflies indoors, although they are not yet effective enough to reduce fly populations to acceptable levels. Therefore, possibilities to improve the effectiveness of these types of traps were examined

Background: Current intra-domiciliary vector control depends on the application of residual insecticides and/or repellents. Although biological control agents have been developed against aquatic mosquito stages, none are available for adults. Following successful use of an entomopathogenic fungus against tsetse flies ( Diptera: Glossinidae) we investigated the potency of this fungus as a biological control agent for adult malaria and filariasis vector mosquitoes. Methods: In the laboratory, both sexes of Anopheles gambiae sensu stricto and Culex quinquefasciatus were passively contaminated with dry conidia of Metarhizium anisopliae. Pathogenicity of this fungus for An. gambiae was further tested for varying exposure times and different doses of oil-formulated conidia. Results: Comparison of Gompertz survival curves and LT50 values for treated and untreated specimens showed that, for both species, infected mosquitoes died significantly earlier ( p

Malaria mosquitoes use host odours to find their blood sources, but little is known about the semiochemicals that mediate this behaviour. A combined study is undertaken to identify the volatile human-specific compounds that are used in the host-seeking behaviour of the females of Anopheles gambiae