Human skin microbiota and their volatiles as odour baits for the malaria mosquito Anopheles gambiae s.s

Abstract

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 semifield conditions and, after fine tuning, have the potential to be developed as odour baits for mosquitoes.

Microorganism-mediated behaviour of malaria mosquitoes

“…gambiae, but not all skin bacterial species attract mosquitoes (Verhulst et al, 2009;Verhulst et al, 2011b). This suggests that An.…”

“…Humans are differentially attractive to malaria mosquitoes based on bacterial species on their skin (Verhulst et al, 2010a). Highly attractive individuals harbour higher densities, but a lower diversity of bacteria on their skin, compared to poorly attractive individuals (Verhulst et al, 2011b). This therefore suggests that attractiveness of humans to mosquitoes based on microbial diversity and/or density can have an effect on the number of mosquito bites received per person, hence the risk of malaria infection (Takken & Knols, 1999).…”

“…The man did not smoke, use perfumed cosmetics, take spicy food or alcohol, and the last shower before sample collection was without soap (Verhulst et al, 2011b Figure. S1).…”

“…These attractive blends have been developed for anthropophilic An. gambiae mosquitoes (Smallegange et al, 2005;Smallegange et al, 2009;Verhulst et al, 2011a;Verhulst et al, 2011b;van Loon et al, 2015). However, less is known about their effect on the host-seeking behaviour of other mosquito species with different host preferences.…”

“…The treatments included a MM-X trap with CO 2 produced by molasses fermentation and (i) clean sock (ii) sock with cow odour (iii) sock with chicken odour (iv) sock with human odour (v) MB5 blend. All the baited MM-X traps were hung outside the bedroom window, under the eaves (Verhulst et al, 2011b). Individual treatments were rotated between the five houses every night.…”