Emerging Daytime Biting Mosquitos: Modeling the Impact of Changing Malaria Vector Behavioral Patterns on the Efficacy of Insecticide Treated Bed-nets

Abstract

Background: Malaria is a life threatening disease caused by Plasmodium parasites and transmitted through the bite of infected female Anopheles mosquito. Implementation of Insecticide Treated Bed-nets (ITNs) in malaria endemic regions has been critical in reducing disease transmission. The success of ITNs is largely dependent on whether mosquitos exhibit endophilic behavior, meaning that they primarily rest and feed indoors. Additionally, the optimum efficacy of ITNs is based on the vectors biting at hours when people are sleeping, or rather, physically under the nets. Recently, research has shown evidence of Anopholes mosquitos biting at earlier times, which is a significant deviation from the generally observed nighttime biting patterns. Objective: Through the development of a novel theoretical framework consisting of three different models, adapted from the classic Ross-Macdonald Malaria Model, this thesis aims to explore how changing mosquito behavioral patterns might influence disease transmission as well as the efficacy of ITNs as an intervention mechanism. The models consider the impact of Wild-type mosquitoes, which display normal nighttime biting patterns, and Mutant mosquitoes, which display daytime biting patterns. Moreover, various scenarios are tested to evaluate the impact of different levels of fitness of the Mutant in relation to the Wild-type. Findings: According to predictions presented by the models, ITN usage plays a critical role in reducing disease transmission in the Wild-type mosquito population interaction with humans. However, ITN usage does not reduce biting activity in the Mutant mosquito. The Mutant mosquito can effectively bite and transmit disease, regardless of its fitness level relative to the Wild-type mosquito. However, when the Mutant mosquito is more fit than the Wild-type mosquito, the population of bitten humans increases significantly. Thus, the emergence of daytime biting mosquitos has the potential to increase human malarial infection. Conclusion: Changes in the vector behavioral patterns present challenges to current malaria intervention measures, which primarily disable mosquitos that feed indoors and at times when susceptible humans are under the protection of ITNs. As such, if daytime biting trends increase, different preventative protocols must be administered to reduce contact and disease transmission in vulnerable human populations.