When a common mosquito faces infection, it appears to change what it drinks from flowers — first seeking nectar laced with mild oxidants, then later favouring antioxidant-rich sips.
In lab tests with Anopheles gambiae infected by the microsporidian parasite Vavraia culicis, researchers offered three choices: plain sugar, sugar plus a small, nectar-like dose of hydrogen peroxide (a pro-oxidant), or sugar plus vitamin C (an antioxidant). The insects didn’t stick to one recipe. Early in infection, they leaned toward the oxidant; later, they pivoted to the antioxidant.
“Younger infected individuals preferred the prooxidant diet, but as they aged, their preference gradually shifted towards the antioxidant diet,” the team writes.
Why that swing? Fighting microbes generates chemical “exhaust” called oxidative stress. A small boost of oxidants can help hold parasites back; too much, for too long, harms the host. The study finds that a brief, early pulse of oxidant feeding cut the share of mosquitoes with detectable spores at day 8 by about 18%, and it added roughly four days to the lives of infected mosquitoes compared with those kept on plain sugar.
In fact, across the board, mosquitoes given the oxidant lived longer than sugar-fed peers, infected and uninfected alike.
The authors interpret the pattern as targeted, time-dependent self-medication: choose a little oxidant when the parasite is multiplying fast, then switch to antioxidants to soften the collateral damage later on.
“These results suggest a form of self-medication, where mosquitoes dynamically adjust their dietary choices throughout infection,” the study notes.
There’s a twist. Healthy mosquitoes generally avoided both the oxidant and antioxidant options when given a choice — yet those that did get the oxidant still lived longer than sugar-only controls. That unexpected boost hints that a mild stress “tune-up” may sometimes help even uninfected insects.
Journal Reference: Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2025.1659.