Modelling the effects of adult emergence on the surveillance and age distribution of medically important mosquitoes

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Résumé

Entomological surveillance is an important component of mosquito-borne disease control.
Mosquito abundance, infection prevalence and the entomological inoculation rate
are the most widely reported entomological metrics, although these data are notoriously
noisy and difficult to interpret. For many infections, only older mosquitoes are infectious,
which is why, in part, vector control tools that reduce mosquito life expectancy have been
so successful. The age structure of wild mosquitoes has been proposed as a metric to
assess the effectiveness of interventions that kill adult mosquitoes, and age grading tools
are becoming increasingly advanced. Mosquito populations show seasonal dynamics
with temporal fluctuations. How seasonal changes in adult mosquito emergence and vector
control could affect the mosquito age distribution or other important metrics is unclear.
We develop stochastic mathematical models of mosquito population dynamics to show
how variability in mosquito emergence causes substantial heterogeneity in the mosquito
age distribution, with low frequency, positively autocorrelated changes in emergence
being the most important driver of this variability. Fitting a population model to mosquito
abundance data collected in experimental hut trials indicates these dynamics are likely
to exist in wild Anopheles gambiae populations. Incorporating age structuring into an
established compartmental model of mosquito dynamics and vector control, indicates
that the use of mosquito age as a metric to assess the efficacy of vector-control tools
will require an understanding of underlying variability in mosquito ages, with the mean
age and other entomological metrics affected by short-term and seasonal fluctuations in
mosquito emergence.

Mots-clés

Adult emergence and variability in the mosquito age distribution