Mosquitoes self-medicate according to the dynamics of a microsporidian infection

Immune responses protect against infectious diseases but often incur costs, such as oxidative stress. In mosquitoes, these costs may drive behaviours that manage oxidative homeostasis, such as self-medicating by consuming nectar containing biologically active substances, including prooxidants and antioxidants. We examined whether Anopheles gambiae mosquitoes adjust their dietary preferences when infected with the microsporidian parasite Vavraia culicis . Using sugar solutions supplemented or not with hydrogen peroxide (a prooxidant) or ascorbic acid (an antioxidant), we assessed the feeding preferences of uninfected and infected mosquitoes at different ages and measured the effects of these diets on oxidative homeostasis and parasite load. Uninfected mosquitoes preferred sugar alone, possibly to avoid oxidative stress caused by the supplemented diets. In contrast, infected mosquitoes initially preferred the prooxidant diet, which reduced parasite load and oxidative stress, but later shifted towards the antioxidant diet, which had little effect on parasite load or oxidative stress. These findings demonstrate that mosquitoes can self-medicate by consuming nectar with appropriate levels of prooxidants and antioxidants, adjusting their preference dynamically with infection progression. Given the role of mosquitoes as major vectors of infectious diseases, these results may have significant public health implications.