Abstract
BackgroundThe control of most vectors of malaria is threatened by the spread of insecticide resistance. One factor that has been hitherto largely overlooked is the potential effects of insecticide resistance on the ability of mosquitoes to transmit malaria: are insecticide-resistant mosquitoes as good vectors of Plasmodium as susceptible ones? The drastic physiological changes that accompany the evolution of insecticide resistance may indeed alter the ability of vectors to transmit diseases, a possibility that, if confirmed, could have major epidemiological consequences.MethodsUsing a novel experimental system consisting of the avian malaria parasite (Plasmodium relictum) and its natural vector (the mosquito Culex pipiens), two of the most common mechanisms of insecticide resistance (esterase overproduction and acetylcholinesterase modification) were investigated for their effect on mosquito infection rate and parasite burden. For this purpose two types of experiments were carried out using (i) insecticide-resistant and susceptible laboratory isogenic lines of Cx. pipiens and (ii) wild Cx. pipiens collected from a population where insecticide resistant and susceptible mosquitoes coexist in sympatry.ResultsThe isogenic line and wild-caught mosquito experiments were highly consistent in showing no effect of either esterase overproduction or of acetylcholinesterase modification on either the infection rate or on the oocyst burden of mosquitoes. The only determinant of these traits was blood meal size, which was similar across the different insecticide resistant categories in both experiments.ConclusionsInsecticide resistance was found to have no effect on Plasmodium development within the mosquito. This is the first time this question has been addressed using a natural mosquito-Plasmodium combination, while taking care to standardize the genetic background against which the insecticide resistance genes operate. Infection rate and oocyst burden are but two of the factors that determine the vectorial capacity of mosquitoes. Other key determinants of parasite transmission, such as mosquito longevity and behaviour, or the parasite's incubation time, need to be investigated before concluding on whether insecticide resistance influences the ability of mosquitoes to transmit malaria.
Highlights
The control of most vectors of malaria is threatened by the spread of insecticide resistance
This study investigates the potential effect of insecticide resistance on Plasmodium infection rate and parasite burden within mosquitoes using the avian malaria parasite, Plasmodium relictum, and its natural mosquito vector, Culex pipiens [21]
This paper aims to reply to the following three questions: 1) Do insecticide resistant mosquitoes have a different probability of infection than susceptible ones? 2) Do infected insecticide resistant mosquitoes attain higher or lower parasite burdens than susceptible ones? and 3) Are these differences dependent on the underlying insecticide resistance mechanism? For this purpose, experimental P. relictum infections were carried out using (i) insecticide-resistant and susceptible laboratory isogenic lines of Cx. pipiens and (ii) wild Cx. pipiens collected from a population where insecticide resistant and susceptible mosquitoes coexist in sympatry
Summary
The control of most vectors of malaria is threatened by the spread of insecticide resistance. Recent work by McCarroll and coworkers [11,12] has shown that insecticide resistance levels in wild Culex quinquefasciatus mosquitoes are negatively correlated with the density of the filarial parasite Wuchereria bancrofti, and that parasite development is blocked at the L1 stage in laboratory mosquitoes selected for artificially high levels of insecticide resistance [11,13]). These results could extend to other mosquito-parasite combinations and have large implications for the transmission of diseases
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
