Résumé
Malaria control strategies aiming at reducing disease transmission intensity
may impact both oocyst intensity and infection prevalence in the mosquito
vector. Thus far, mathematical models failed to identify a clear relationship
between Plasmodium falciparum gametocytes and their infectiousness to
mosquitoes. Natural isolates of gametocytes are genetically diverse and
biologically complex. Infectiousness to mosquitoes relies on multiple
parameters such as density, sex-ratio, maturity, parasite genotypes and host
immune factors. In this article, we investigated how density and genetic
diversity of gametocytes impact on the success of transmission in the mosquito
vector. We analyzed data for which the number of covariates plus attendant
interactions is at least of order of the sample size, precluding usage of
classical models such as general linear models. We then considered the variable
importance from random forests to address the problem of selecting the most
influent variables. The selected covariates were assessed in the zero inflated
negative binomial model which accommodates both over-dispersion and the sources
of non infected mosquitoes. We found that the most important covariates related
to infection prevalence and parasite intensity are gametocyte density and
multiplicity of infection.