Résumé
The population dynamics of human to mosquito malaria transmission in the
field has important implica- tions for the genetics, epidemiology and
control of malaria. The number of oocysts in oocyst-positive mosquitoes
developing from a single, naturally acquired infectious blood meal (herein
referred to as a single-feed infection load) greatly influences the
efficacy of transmission blocking interventions but still remains poorly
documented. During a year-long analysis of malaria parasite transmission
in Burkina Faso we caught and dissected wild malaria vectors to
assess Plasmodium oocyst prevalence and load (the number
of oocysts counted in mosquitoes with detectable oocysts) and the
prevalence of salivary gland sporozoites. This was compared with malaria
endemicity in the human population, assessed in cross-sectional surveys.
Data were analysed using a novel transmission mathematical model to
estimate the per bite transmission probability and the average single-feed
infection load for each location. The observed oocyst load and the
estimated single-feed infection load in naturally infected mosquitoes were
substantially higher than previous estimates (means ranging from 3.2 to
24.5 according to seasons and locations) and indicate a strong positive
association between the single-feed infection load and parasite prevalence
in humans. This work suggests that highly infected mosquitoes are not rare
in the field and might have a greater influence on the epidemiology and
genetics of the parasite, and on the efficacy of novel transmission
blocking interventions.