Abstract:
BACKGROUND : Survival and gonotrophic cycle duration are important determinants of
the vectorial capacity of malaria vectors but there are a limited number of approaches
to estimate these quantities from field data. Time-series of observations of
mosquitoes at different stages in the life-cycle are under-used.
METHODS : Anopheles funestus mosquitoes were caught using various methods over a
7.6-year period in Furvela, Mozambique. Survival and oviposition cycle duration
were estimated using (i) an existing time-series approach for analysing dissections of
mosquitoes caught in light-traps, extended to allow for variability in the duration of
the cycle; (ii) an established approach for estimating cycle duration from resting
collection data; (iii) a novel time-series approach fitted to numbers and categories of
mosquitoes caught in exit-traps.
RESULTS : Data were available from 7,396, 6,041 and 1,527 trap-nights for exit-traps,
light-traps and resting collections respectively. Estimates of cycle duration varied
considerably between the different methods. The estimated proportion of female
mosquitoes surviving each day of 0.740 (95% credible interval [0.650–0.815]) derived
from light-trap data was much lower than the estimated daily survival of male
mosquitoes from the model fitted to exit-trap data (0.881, 95% credible interval
[0.747–0.987]). There was no tendency for the oviposition cycle to become shorter at
higher temperature while the odds of survival of females through the cycle was
estimated to be multiplied by 1.021 for every degree of mean weekly temperature
increase (95% credible interval [0.991–1.051]). There was negligible temperature dependence and little inter-annual variation in male survival.
DISCUSSION : The time-series approach fitted to the exit-traps suggests that male An.
funestus have higher survival than do females, and that male survival was
temperature independent and unaffected by the introduction of long-lasting
insecticidal nets (LLINs). The patterns of temperature dependence in females are at
variance with results of laboratory studies. Time series approaches have the advantage for estimating survival that they do not depend on representative sampling
of mosquitoes over the whole year. However, the estimates of oviposition cycle
duration were associated with considerable uncertainty, which appears to be due to
variability between insects in the duration of the resting period, and the estimates
based on exit-trap data are sensitive to assumptions about relative trapping
efficiencies.
Description:
DATA AVAILABILITY : The following information was supplied regarding data availability:
The data and code are available at GitHub and Zenodo: https://github.com/ThomasASmith/Furvela_Entomology, this repository includes a
codebook that provides an English translation of Portuguese terminology.
ThomasASmith. (2023). ThomasASmith/Furvela_Entomology: Entomology data and
code for Furvela, Mozambique (v1.0). Zenodo. https://doi.org/10.5281/zenodo.7607159.