The Influence of Physiological Status on age Prediction of Anopheles Arabiensis Using Near Infra-red spectroscopy

Determining the age of malaria vectors is essential for evaluating the impact of interventions that reduce the survival of wild mosquito populations and for estimating changes in vectorial capacity. Near infra-red spectroscopy (NIRS) is a simple and non-destructive method that has been used to determine the age and species of Anopheles gambiae s.l. by analyzing differences in absorption spectra. The spectra are affected by biochemical changes that occur during the life of a mosquito and could be influenced by senescence and also the life history of the mosquito, i.e., mating, blood feeding and egg-laying events. To better understand these changes, we evaluated the influence of mosquito physiological status on NIR energy absorption spectra. Mosquitoes were kept in individual cups to permit record keeping of each individual insect’s life history. Mosquitoes of the same chronological age, but at different physiological stages, were scanned and compared using cross-validations. We observed a slight trend within some physiological stages that suggest older insects tend to be predicted as being physiologically more mature. It was advantageous to include mosquitoes of different chronological ages and physiological stages in calibrations, as it increases the robustness of the model resulting in better age predictions. Progression through different physiological statuses of An. arabiensis influences the chronological age prediction by the NIRS. Entomologists that wish to use NIR technology to predict the age of field-caught An. gambiae s.l from their study area should use a calibration developed from their field strain using mosquitoes of diverse chronological ages and physiological stages to increase the robustness and accuracy of the predictions.\u

Eave tubes for malaria control in Africa : an introduction

In spite of massive progress in the control of African malaria since the turn of the century, there is a clear and recognized need for additional tools beyond long-lasting insecticide-treated bed nets (LLINs) and indoor residual spraying (IRS) of insecticides, to progress towards elimination. Moreover, widespread and intensifying insecticide resistance requires alternative control agents and delivery systems to enable development of effective insecticide resistance management strategies. This series of articles presents a novel concept for malaria vector control, the ‘eave tube’, which may fulfil these important criteria. From its conceptualization to laboratory and semi-field testing, to demonstration of potential for implementation, the stepwise development of this new vector control approach is described. These studies suggest eave tubes (which comprise a novel way of delivering insecticides plus screening to make the house more ‘mosquito proof’) could be a viable, cost-effective, and acceptable control tool for endophilic and endophagic anophelines, and possibly other (nuisance) mosquitoes. The approach could be applicable in a wide variety of housing in sub-Saharan Africa, and possibly beyond, for vectors that use the eave as their primary house entry point. The results presented in these articles were generated during an EU-FP7 funded project, the mosquito contamination device (MCD) project, which ran between 2012 and 2015. This was a collaborative project undertaken by vector biologists, product developers, modellers, materials scientists, and entrepreneurs from five different countries

The impact of livestock on the abundance, resting behaviour and sporozoite rate of malaria vectors in southern Tanzania

Background\ud \ud Increases in the coverage of long-lasting insecticidal nets (LLINs) have significantly reduced the abundance of Anopheles gambiae sensu stricto in several African settings, leaving its more zoophagic sibling species Anopheles arabiensis as the primary vector. This study investigated the impact of livestock ownership at the household level on the ecology and malaria infection rate of vectors in an area of Tanzania where An. arabiensis accounts for most malaria transmission.\ud \ud Methods\ud \ud Mosquito vectors were collected resting inside houses, animal sheds and in outdoor resting boxes at households with and without livestock over three years in ten villages of the Kilombero Valley, Tanzania. Additionally, the abundance and sporozoite rate of vectors attempting to bite indoors at these households was assessed as an index of malaria exposure.\ud \ud Results\ud \ud The mean abundance of An. gambiae s.l. biting indoors was similar at houses with and without livestock. In all years but one, the relative proportion of An. arabiensis within the An. gambiae s.l. species complex was higher at households with livestock. Livestock presence had a significant impact on malaria vector feeding and resting behaviour. Anopheles arabiensis were generally found resting in cattle sheds where livestock were present, and inside houses when absent. Correspondingly, the human blood index of An. arabiensis and An. funestus s.l. was significant reduced at households with livestock, whereas that of An. gambiae s.s. was unaffected.\ud \ud Whilst there was some evidence that sporozoite rates within the indoor-biting An. gambiae s.l population was significantly reduced at households with livestock, the significance of this effect varied depending on how background spatial variation was accounted for.\ud \ud Conclusions\ud \ud These results confirm that the presence of cattle at the household level can significantly alter the local species composition, feeding and resting behaviour of malaria vectors. However, the net impact of this livestock-associated variation in mosquito ecology on malaria exposure risk was unclear. Further investigation is required to distinguish whether the apparently lower sporozoite rates observed in An. gambiae s.l. at households with livestock is really a direct effect of cattle presence, or an indirect consequence of reduced risk within areas where livestock keepers choose to live