High Plasmodium infection intensity in naturally infected malaria vectors in Africa

Detection of Plasmodium falciparum in laboratory-reared and naturally infected wild mosquitoes using near-infrared spectroscopy

“…The villages of Longo and Klesso were 120 km apart to allow the robustness of the method over space to be assessed. In addition to being easily accessibility from Bobo-Dioulasso, these two villages had mosquito and human prevalence well characterized in a previous study (Bompard et al 13 ). Wild mosquitoes were caught early in the morning by the technicians using a mouth aspirator in the living room of human dwellings 24 and transferred to the laboratory.…”

“…They were maintained in cages (30 × 30 × 30 cm) in laboratory conditions (28 °C ± 2, 80% ± 05 RH with 10% glucose solution) during 3 or 7 days periods before the next step. These days were chosen to allow mosquitoes to digest their last blood-meal (to enable dissection and enumeration of oocysts), increase the number of sporozoite positive mosquitoes and match previous work (Bompard et al 13 ). At these indicated periods, the Anopheles females were scanned using the spectrometer and their midgut was immediately dissected under a stereomicroscope to determine oocyst prevalence.…”

“…It is unclear whether NIRS is detecting the presence of parasite biomass or a physiological change in the mosquito. Here we devise a comprehensive set of experiments which would enable the differentiation of mosquitoes which (1) have fed on malaria infected blood, (2) are infected with oocyst life-stages (visible in Burkina Faso from 3 to 11 days from infection) 13 and (3) are infectious with salivary gland sporozoites. Sporozoites are the most epidemiologically important parasite life stage although evaluation of control interventions might be easier with earlier life-stages which have a higher prevalence in wild mosquito populations and therefore require lower number of mosquitoes to generate sufficiently precise estimates.…”

Plasmodium oocysts respond with dormancy to crowding and nutritional stress

“…We demonstrate that under starvation conditions, when an oocyst-harbouring mosquito is deprived of supplemental bloodmeals, infection intensity plays a major role in oocyst growth, as measured by both DNA content and oocyst size. Mosquitoes harbouring many oocysts, a condition that can occur naturally in field infections 20 and invariably in experimental infections and which can be further elevated by inactivating the mosquito immune response, exhibit substantial variability in oocyst growth. In such conditions of crowding and nutritional stress, expression of parasite pre-tRNA Tyr is significantly reduced, indicating that the oocyst enters a dormancy-like state of slowed metabolic activity.…”

Detection of Plasmodium Falciparum in Laboratory and Naturally Infected Mosquitoes Using Near-infrared Spectroscopy

“…It is unclear whether NIRS is detecting the presence of parasite biomass or a physiological change in the mosquito. Here we devise a comprehensive set of experiments which would enable the differentiation of mosquitoes which (i) have fed on malaria infected blood, (ii) are infected with oocyst life-stages (visible in Burkina Faso from 3-11 days from infection) 13 and (iii) are infectious with salivary gland sporozoites. Sporozoites are the most epidemiologically important parasite life stage although evaluation of control interventions might be easier with earlier life-stages which have a higher prevalence in wild mosquito populations and therefore require lower number of mosquitoes to generate sufficiently precise estimates.…”