Paaijmans, K.P., Blanford, S., Chan, B.H.K. and Thomas, M.B. 2012. Warmer temperatures reduce the vectorial capacity of malaria mosquitoes. Biology Letters 8: 465-468.
The authors write that "the development rate of parasites and pathogens within vectors typically increases with temperature," and, therefore, they say that "transmission intensity is generally assumed to be higher under warmer conditions." However, they indicate that "development is only one component of parasite/pathogen life history," and they note that "there has been little research exploring the temperature sensitivity of other traits that contribute to transmission intensity."
What was done
Working to fill this knowledge void with the rodent malaria Plasmodium yoelii and the Asian malaria vector Anopheles stephensi, Paaijmans et al. examined prior "standard assumptions" and explored the resulting implications "for our understanding of the effects of temperature on disease transmission."
What was learned
The three U.S. researchers report they were able to show, first of all, that "vector competence (the maximum proportion of infectious mosquitoes, which implicitly includes parasite survival across the incubation period) tails off at higher temperatures, even though parasite development rate increases." Secondly, they again say they were able to show that "the standard measure of the parasite incubation period (i.e., time until the first mosquitoes within a cohort become infectious following an infected blood-meal) is incomplete because parasite development follows a cumulative distribution, which itself varies with temperature." And "including these effects in a simple model," in their words, "dramatically alters estimates of transmission intensity and reduces the optimum temperature for transmission."
What it means
Paaijmans et al. state that their results "challenge current understanding of the effects of temperature on malaria transmission dynamics," and they note that their findings imply that "control at higher temperatures might be more feasible than currently predicted." Therefore, in regard to "the possible effects of climate warming," they conclude that "increases in temperature need not simply lead to increases in transmission."