The effect of Mycobacterium ulcerans exotoxin on host-seeking and oviposition behavior of Aedes aegypti aegypti (L.) (Diptera: Culicidae)

Buruli Ulcer (BU) is an emerging tropical disease, affecting many individuals  throughout the world, with highest prevalence  in West Africa.  BU is caused by the environmental pathogen, Mycobacterium ulcerans, which produces a toxin called mycolactone that diffuses through healthy tissue leading to ulceration covering up to 15% of the body. BU and M. ulcerans are associated with aquatic habitats, however the mode of M. ulcerans transmission is not known. Additionally, the biological role of mycolactone remains unsolved.  This study examined if mycolactone is an attractant to the mosquito Aedes aegypti aegypti (Linnaeus) (Diptera: Culicidae) for host-seeking behavior, and oviposition site choice. Responses of adult mosquitoes to a blood-feeder or an oviposition substrate treated with three mycolactone concentrations (0.05, 0.5, or 1.0 μg/mL) or ethanol control were examined. Results showed mosquitoes were more attracted (29.1%) to the blood-feeder treated with the highest dose over the control. Additionally and interestingly, mosquitoes were attracted (~15%) to the oviposition site treated with the high dose, but were more attracted to the control (~30%) rather than the low or medium doses, indicating a possible repellant for mosquitoes to oviposit in sites with lower mycolactone concentrations. These data indicate that mycolactone could serve as an attractant to mosquitoes, which could result in transmission of the pathogen responsible for BU as well as enhance the transmission of other vector-borne pathogens such as yellow fever Future studies would provide greater insight into the role mycolactone serves as an attractant, and what threshold induces a shift in mosquito behavior.