Some like it hot: A differential response to changing temperatures by the malaria vectors Anopheles funestus and An. gambiae s.l.
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Abstract
Background: With the possible implications of global warming, the effect of temperature on the dynamics of malaria vectors in Africa has become a subject of increasing interest. Information from the field is, however, relatively sparse. We describe the effect of ambient temperature over a five-year period on the dynamics of An. funestus and An. gambiae s.l., collected from a single village in southern Mozambique where temperatures varied from a night-time minimum of 6oC in the cool season to a daytime maximum of 35oC in the hot season. Results: Mean daily air temperatures varied from 34o C to 20oC and soil temperatures varied from 26 o C to 12 o C. Diurnal variation was greatest in the cooler months of the year and were greater in air temperatures than soil temperatures. During the study 301, 705 female An. funestus were collected in 6043 light-trap collections, 161, 466 in 7397 exit collections and 16, 995 in 1315 resting collections. The equivalent numbers for An. gambiae s.l. are 72, 475 in light-traps, 33, 868 in exit collections and 5, 333 from indoor resting collections. Numbers of mosquito were greatest in the warmer months. Numbers of An. gambiae s.l. went through a one hundredfold change (from a mean of 0.14 mosquitoes a night to 14) whereas numbers of An. funestus merely doubled (from a mean of 20 to 40 a night). The highest environmental correlations and mosquito numbers were between mean air temperature (r2 = 0.52 for An. funestus and 0.77 for An. gambiae s.l.). Numbers of mosquito collected were not related to rainfall with lags of up to four weeks. Numbers of both gravid and unfed An. gambiae complex females in exit collections continued to increase at all temperatures recorded but gravid females of An. funestus decreased at temperatures above 28oC. Overall the numbers of gravid and unfed An. funestus collected in exit collections were not correlated (p = 0.07). For an unknown reason the number of An. gambiae s.l. fell below monitoring thresholds during the study. Conclusions: Mean air temperature was the most important environmental parameter affecting both vectors in this part of Mozambique. Numbers of An. gambiae s.l. increased at all temperatures recorded whilst An. funestus appeared to be adversely affected by temperatures of 28oC and above. These differences may influence the distribution of the vectors as the planet warms.
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2016. Some like it hot: A differential response to changing temperatures by the malaria vectors Anopheles funestus and An. gambiae s.l. PeerJ Preprints 4:e2011v1 https://doi.org/10.7287/peerj.preprints.2011v1note This preprint is not peer-reviewed. You may wish to reference the subsequent peer-reviewed version of this article.
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This is a submission to PeerJ for review.
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Supplemental Information
Complete correlation coefficients for environmental variables and mosquito numbers
Environmental data from Furvela village
Hourly data from the Delta logger in Furvela village, Mozambique
Additional Information
Competing Interests
The author declares that he has no competing interests.
Author Contributions
Jacques D Charlwood conceived and designed the experiments, performed the experiments, analyzed the data, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Human Ethics
The following information was supplied relating to ethical approvals (i.e., approving body and any reference numbers):
Ethical clearance from the National Bioethics Committee of Mozambique on 2 April 2001 (ref: 056/CNBS/01). Householders were informed about the purpose of the collections. Verbal consent was obtained when collections were initiated.
Data Deposition
The following information was supplied regarding data availability:
The raw data has been supplied as a Supplemental Dataset.
Funding
This work was funded by the Danish Bilharziasis Laboratory, Denmark. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
