Regulation of diel locomotor activity and retinal responses of Anopheles stephensi by ingested histamine and serotonin is temperature- and infection-dependent.

Disrupting behaviors linked to movement of primary mosquito vectors, such as diel locomotor activity and visual sensitivity, is a novel and plausible malaria control intervention. Diel locomotor activity is an output of arthropod circadian activity and is influenced by factors such as light, temperature, and infection status. The biogenic amines histamine and serotonin (5-HT) are ingested with blood and differ between healthy hosts and those with severe malaria. They regulate malaria parasite infection in Anopheles stephensi, but the degree to which aging, temperature, and infection interact with ingested biogenic amines to influence mosquito behavior was unknown prior to these studies. We provisioned A. stephensi with histamine and 5-HT at healthy- and malaria-associated levels to examine diel locomotor activity of uninfected A. stephensi across lifespan, at temperatures that A. stephensi could encounter within its range, and on Plasmodium yoelii-infected mosquitoes during sporogony. We further evaluated treatment effects on retinal sensitivity of uninfected mosquitoes during light and dark periods typically associated with low and high activity for this crepuscular species. Treatment with malaria-associated levels of histamine and 5-HT significantly increased the locomotor activity of A. stephensi across lifespan and enhanced retinal sensitivity to a broad spectrum of wavelengths at the onset of light. This treatment in combination with higher temperatures also increased activity levels and broadened the peak hours of activity of A. stephensi. Notably, these effects were infection dependent. Together, our data suggest that histaminergic and serotonergic signaling within the gut-brain axis of A. stephensi could be targeted to alter mosquito activity and visual sensitivity as the basis for novel transmission-blocking strategies for malaria control.