Artificial nighttime lighting impacts Plasmodium falciparum mature stage V gametocytes infectivity in Anopheles stephensi

Abstract

Abstract Background: Malaria is one of the most important vector-borne diseases of humans with an estimated 241 million cases worldwide in 2020. As an urban and periurban mosquito species, An. stephensi is exposed to artificial human stimuli like light that can alter many aspects of mosquito behavior, physiology and metabolism. Therefore, fluctuations in the light environment may influence the host, parasite and/or mosquito biology and hence modulate risk for disease transmission. In this study, we have tested the effect of artifitial light at night on mosquito infectivity by Plasmodium falciparum during the first hours of blood digestion. Methods: A total of three independent Standard Membrane Feeding Assays were performed to artificially fed septic and aseptic mosquitoes with P. falciparuminfected blood. After blood feeding, females were transferred to incubators with different photoperiod cycles, so digestion occurred under day artificial light or dark. At 7 and 16 days post blood feeding, mosquitoes were dissected for midguts and salivary glands respectively. Percentage of mosquitoes fed, percentage of prevalence and P. falciparum oocyst intensity between septic and aseptic mosquitoes in the two different photoperiod regimes were compared using a non-parametric ANOVA followed by a Dunn´s multiple comparison test. Results: The exposition of mosquitoes to light after they took an infected blood meal will have a negative effect on the successful progression of P. falciparumin the mosquito midgut. Antibiotic treatment significantly incremented the number of oocysts per midgut. Photophase significantly reduced the median oocyst intensity in both septic and aseptic mosquitoes. The percentage of oocyst reduction, understood as the percentage of reduction in the mean oocyst intensity of the parasite in the mosquito midgut between photophase and scotophase, was 51% in the case of aseptic mosquitoes and 80% for septic mosquitoes, both in the photophase condition. Conclusion: Although still there are a lot of gaps in the understanding of parasite-mosquito interactions, our results support the idea that light can not only influence mosquito biting behavior but also parasite success in the mosquito midgut. Hence, light can be considered an interesting additional mosquito-control strategy to reduce mosquito-borne diseases.