Mycobacterium ulcerans toxin, mycolactone may enhance host‐seeking and oviposition behaviour by Aedes aegypti (L.) (Diptera: Culicidae)

Abstract

The ecological functions of many toxins continue to remain unknown for those produced by environmental pathogens. Mycobacterium ulcerans, the causative agent of the neglected tropical disease, Buruli ulcer, produces a cytotoxic macrolide, mycolactone, whose function(s) in the environment remains elusive. Through a series of dual-choice behaviour assays, they show that mycolactone may be an interkingdom cue for the yellow fever mosquito, Aedes aegypti, seeking blood-meals as well as oviposition sites. Results provide novel insight into the evolution between bacteria and potential vectors. While further studies are needed to determine if mycolactone is an actual signal rather than simply a cue, this discovery could serve as a model for determining roles for toxins produced by other environmental pathogens and provide opportunities for developing novel strategies for disease prevention. The relationship between M. ulcerans, mycolactone, and Ae. aegypti further suggests there could be an amplification effect for the spread of pathogens responsible for other diseases, such as yellow fever and dengue.

Impact of mycolactone produced by Mycobacterium ulcerans on life-history traits of Aedes aegypti (L.) and resulting habitat selection for oviposition

“…A recent study in our laboratories demonstrated mycolactone influences behavior of the yellow fever mosquito, Aedes aegypti aegypti, (L.) (Diptera: Culicidae) (Sanders et al, 2017), which occurs in similar environments (Garnham et al, 1946;Christophers, 1960) as M. ulcerans (Williamson et al, 2012). In the study, 29% more were attracted to blood-feeders treated with 1.0 µg/ml mycolactone compared to control feeders.…”

“…All experiments were conducted under the laboratory conditions previously described (Sanders et al, 2017). For the larval growth/ survivorship assay, 40 Ae.…”

“…In the study, 29% more were attracted to blood-feeders treated with 1.0 µg/ml mycolactone compared to control feeders. They further demonstrated naïve mosquitoes (never exposed to M. ulcerans or mycolactone) preferred to oviposit (64%) in areas containing mycolactone at the same concentration (1.0 µg/ml) that enhanced attraction to the blood-feeders (Sanders et al, 2017). However, the impact of mycolactone on subsequent mosquito development and resulting adult behavior is not known.…”

Evidences of the Low Implication of Mosquitoes in the Transmission ofMycobacterium ulcerans, the Causative Agent of Buruli Ulcer

“…The traumatized skin should initially be colonized by MU , a phenomenon that could naturally happen during repetitive contacts with the risk environments such as water bodies or contaminated biofilms [ 1 , 17 , 28 ]. Furthermore, in behavioral study with Aedes aegypti , Sanders et al [ 50 ] suggested that if a biofilm of MU was on a person, the bacteria may be attracting mosquitoes which in return would lead to a puncture insertion of MU as recently reported by Wallace et al [ 28 ]. Although mechanical transmission of MU stands as a common mechanism that could correlate transmission studies from both Africa and Australia, Williamson et al [ 30 ] recently established that abrasions (trauma) of the skin in Guinea pig models and subsequent application of MU are not sufficient enough to cause an ulcer.…”

Understanding the transmission of Mycobacterium ulcerans: A step towards controlling Buruli ulcer

“…Other experimental studies suggest that mycolactone may serve as a potential attractant for mosquitoes, thereby facilitating M . ulcerans transmission [ 90 , 91 ]. Ultimately, further experimental and observational studies are needed to establish vector competence.…”