Chemosensory responses to the repellent nepeta essential oil and its major component nepetalactone by the yellow fever mosquito, aedes aegypti, a vector of zika virus

Authors: Sparks, Jackson; Bohbot, Jonathan; RISTIC, MIHAILO - University Of Belgrade; MISIC, DANIJELA - University Of Belgrade; SKORIC, MARIJANA - University Of Belgrade; Mattoo, Autar; Dickens, Joseph

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2017
Publication Date: 4/12/2017
Citation: Sparks, J.T., Bohbot, J.D., Ristic, M., Misic, D., Skoric, M., Mattoo, A.K., Dickens, J.C. 2017. Chemosensory responses to the repellent nepeta essential oil and its major component nepetalactone by the yellow fever mosquito, aedes aegypti, a vector of zika virus. Journal of Medical Entomology. doi: 10.1093/jme/tjx059.

Interpretive Summary: Catnip has long been known for its attraction to cats and its repellent effects on many insects. Both catnip essential oil and its major chemical component nepetalactone repel mosquitoes from a distance and deter feeding, thus providing protection from diseases vectored by the mosquitoes. However, the neural mechanisms through which catnip exerts its effects on mosquitoes were largely unknown. Here we show in the yellow-fever mosquito, a vector of Zika virus, that certain smell and taste receptor cells detect catnip, thus providing sensory pathways for its effects. High concentrations of catnip volatiles elicit responses from smell cells on the maxillary palps. Taste cells on the elongated mouthparts respond to catnip essential oil and nepetalactone, and the chemicals further exert their effects by decreasing responses to a feeding stimulant. Our results provide neural pathways for the reported spatial repellency and feeding deterrence of these repellents. Knowledge of the mechanism by which catnip has its effects may be used by entomologists and molecular biologists to screen chemicals in an effort to discover novel repellents for protection of humans and animals from disease vectors.

Technical Abstract: Nepeta essential oil (Neo) (catnip) and its major component, nepetalactone, have long been known to repel insects including mosquitoes. However, the neural mechanisms through which these repellents are detected by mosquitoes, including the yellow fever mosquito Aedes aegypti, an important vector of Zika virus, were poorly understood. Here we show that Neo volatiles activate olfactory receptor neurons within the basiconic sensilla on the maxillary palps of female Ae. aegypti. A gustatory receptor neuron sensitive to the feeding deterrent quinine and housed within sensilla on the labella of females was activated by both Neo and nepetalactone. Activity of a second gustatory receptor neuron sensitive to the feeding stimulant sucrose was suppressed by both repellents. Our results provide neural pathways for the reported spatial repellency and feeding deterrence of these repellents. A better understanding of the neural input through which female mosquitoes make decisions to feed will facilitate design of new repellents and management strategies involving the use of repellents.