Differential Responses of Anopheles Stephensi (Diptera: Culicidae) to Skin Emanations of a Man, a Cow, and a Guinea Pig in the Olfactometer

Background: Biting habit of mosquitoes plays an important role in the epidemiology of mosquito-borne diseases. Mos qui toes use a set of elaborate sensory modalities to find their preferred hosts by exploiting cues emanating from a nearby host. It has been suggested that the chemical profile of skin can provide further support for anthropophilic mos quito species to find their suitable hosts. This study aimed at revealing the value of skin emanation for a zoo-philic species like Anopheles stephensi as a model. Methods: Skin emanations of a man, a cow and a Guinea pig were collected by ethanol soaked cottons. Upwind re-sponses of mosquitoes to 100 and 200 µl of filtered skin materials were non-competitively explored in a dual-choice ol fac tometer. L-lactic acid and other chemical content of the skin samples were identified by an enzymatic kit and GC-MS, respectively. Results: Unexpectedly, only human skin emanation was resulted in the statistically significant activation and attrac-tion responses of An. stephensi in the wind tunnel. L-lactic acid content of this skin sample was 10 and 29 times more than the cow and the Guinea pig, respectively. The possible role of lactic acid and a few other identified com-pounds have been discussed here. Conclusion: Anopheles stephensi showed higher and more specific upwind responses to human skin emanation in the ol factome ter. Undoubtedly, the thorough explanation of this unexpected finding needs further investigation. But, if new data verify this result, then, it may be necessary to reconsider the role of skin emanation and thence the human blood index and vectorial capacity of this zoophilic mosquito.