Transient Tolerance to Pyrethroids in Gravid Mosquitoes

Innovation stemming from research is clearly the path to future progress in pursuit of resistance-breaking interventions for vector control. Mark Clifton, Executive Director of Chicago’s North Shore Mosquito Abatement District, has developed a reputation for insightful field work – a portion of which is devoted to addressing the insecticide resistance paradox.

“When resistant mosquitos are gravid, they are half as susceptible to synergized pyrethroids.”

At the 2022 Global Mosquito Resistance Management Summit (GMRMS), Clifton gave the audience a sneak preview of fascinating, unpublished data from a new project he’s working on – examining resistance from the perspective of varying physiological states of the insect, stages of cyclically host-seeking, feeding and laying eggs.

Click on image to enlarge

Pointing to work by Chester Moore in 1990, Clifton discussed how an individual’s relative susceptibility to pesticides varies widely across these states, and that a dramatic reduction in susceptibility immediately follows a bloodmeal, a reduction which dissipates over time before the cycle repeats. Using an adapted model from Moore, Clifton used simulated data to demonstrate outcomes based on variable susceptibility at 10, day-long life stages from emergence to egg-laying; five of which repeat for the life of the insect as it seeks a host, digests a bloodmeal and lays eggs.

As part of his work, Clifton introduced the effects of a resistant population into the model. Early learning suggests that these effects have profound implications with respect to application timing and disease transmission.

In Contrast, Clifton showed a side-by-side of a comparable application program versus a 95% susceptible population, from which implications of disease incidence could by implied. Public Health Landscape is actively monitoring these studies.