Stable and fluctuating temperature effects on the development rate and survival of two malaria vectors, Anopheles arabiensis and Anopheles funestus

Abstract

BackgroundUnderstanding the biology of malaria vector mosquitoes is crucial to understanding many aspects of the disease, including control and future outcomes. The development rates and survival of two Afrotropical malaria vectors, Anopheles arabiensis and Anopheles funestus, are investigated here under conditions of constant and fluctuating temperatures. These data can provide a good starting point for modelling population level consequences of temperature change associated with climate change. For comparative purposes, these data were considered explicitly in the context of those available for the third African malaria vector, Anopheles gambiae.MethodsTwenty five replicates of 20–30 eggs were placed at nine constant and two fluctuating temperatures for development rate experiments and survival estimates. Various developmental parameters were estimated from the data, using standard approaches.ResultsLower development threshold (LDT) for both species was estimated at 13-14°C. Anopheles arabiensis developed consistently faster than An. funestus. Optimum temperature (Topt) and development rate at this temperature (μmax) differed significantly between species for overall development and larval development. However, Topt and μmax for pupal development did not differ significantly between species. Development rate and survival of An. funestus was negatively influenced by fluctuating temperatures. By contrast, development rate of An. arabiensis at fluctuating temperatures either did not differ from constant temperatures or was significantly faster. Survival of this species declined by c. 10% at the 15°C to 35°C fluctuating temperature regime, but was not significantly different between the constant 25°C and the fluctuating 20°C to 30°C treatment. By comparison, previous data for An. gambiae indicated fastest development at a constant temperature of 28°C and highest survival at 24°C.ConclusionsThe three most important African malaria vectors all differ significantly in development rates and survival under different temperature treatments, in keeping with known distribution data, though differences among M and S molecular forms of An. gambiae likely complicate the picture. Increasing temperatures associated with climate change favour all three species, but fluctuations in temperatures are detrimental to An. funestus and may also be for An. gambiae. This may have significant implications for disease burden in areas where each species is the main malaria vector.

Desiccation tolerance as a function of age, sex, humidity and temperature in adults of the African malaria vectorsAnopheles arabiensisPatton andAnopheles funestusGiles

“…Tompkins and Ermert, 2013). Thus, in conjunction with information on thermal effects on development in the immatures and survival in adults (Lyons et al, 2012;Lyons et al, 2013), this information will improve current malaria forecasting abilities, especially in southern Africa.…”

Temperature during larval development and adult maintenance influences the survival of Anopheles gambiae s.s.

“…In addition, Anopheles gambiae s.s. is only one of seven dominant vector species of human malaria on the African continent [50], and data regarding the sensitivity of these other species to temperature and other climateand population-related factors are equally sparse, if not more so. Climate change is likely to influence the survival [51] and life-history parameters of different species of malaria vectors in different manners [52]. More extensive, species-specific data on the dependency of mosquito life-history parameters and population dynamics on climatic conditions, when coupled with geographicallydetailed climate predictions, will enable more robust and reliable predictions of vector population dynamics and disease transmission.…”

Climate Change and the Crystal Ball of Vector-Borne Disease Forecasts

“…funestus did worse with fluctuating temperatures whereas An. arabiensis either did the same or better as temperatures varied [10].…”