Rodent malaria-resistant strains of the mosquito, <i>Anopheles gambiae</i>, have slower population growth than -susceptible strains

<b>Background</b> <br> Trade-offs between anti-parasite defence mechanisms and other life history traits limit the evolution of host resistance to parasites and have important implications for understanding diseases such as malaria. Mosquitoes have not evolved complete resistance to malaria parasites and one hypothesis is that anti-malaria defence mechanisms are costly. <br> <b>Results</b> <br> We used matrix population models to compare the population growth rates among lines of <i>Anopheles</i> gambiae that had been selected for resistance or high susceptibility to the rodent malaria parasite, <i>Plasmodium yoelii nigeriensis</i>. The population growth rate of the resistant line was significantly lower than that of the highly susceptible and the unselected control lines, regardless of whether mosquitoes were infected with <i>Plasmodium</i> or not. The lower population growth of malaria-resistant mosquitoes was caused by reduced post blood-feeding survival of females and poor egg hatching. <br> <b>Conclusions</b> <br> With respect to eradicating malaria, the strategy of releasing <i>Plasmodium</i>-resistant <i>Anopheles</i> mosquitoes is unlikely to be successful if the costs of <i>Plasmodium</i>-resistance in the field are as great as the ones measured in this study. High densities of malaria-resistant mosquitoes would have to be maintained by continuous release from captive breeding facilities.