Model points to promise of combined malaria control
[CAIRO] Combining methods of malaria control that hit mosquitoes at different stages of their life cycle could slash malaria transmission, a model has determined.
Using both insecticide-treated bednets (ITNs) and new fungal biopesticides could have a substantial effect on disease prevalence, even in situations where neither intervention would have much impact alone, according to the research published in PLoS Computational Biology earlier this month (2 October).
This strategy may prove particularly beneficial in high transmission areas with insecticide resistance problems, partly because fungal biopesticides are able to reverse resistance, according to the study (see Fungi beat insecticide resistance in mosquitoes).
Using data from laboratory and field studies, the digital model — developed by Penelope Hancock, a researcher at Imperial College London, United Kingdom — estimates the impact of fungal infection and ITN use on the mosquito feeding and life cycles.
ITNs affect mosquitoes during their host-seeking phase by preventing them from feeding on people. In contrast, fungal biopesticides target mosquitoes at a range of lifecycle points, reducing the insects' ability to fly and feed, and impairing their metabolic functioning in the non-feeding phase.
Matt Thomas, professor of entomology at the Center for Infectious Disease Dynamics at Penn State University, United States, and co-author of the study showing that the biopesticides reverse resistance, describes Hancock's work as "exciting".
He says her model is innovative in the way it breaks the biology of mosquitoes and malaria transmission down to the level of mosquito feeding cycles.
"Models such as this are great for framing the problem and exploring the possibilities," he says.
Hancock says her model could be adapted to compare other combinations of malaria control methods. The next step is to compare its results with those from field trials.
But Clive J. Shiff, associate professor at the John Hopkins Center for Global Health, harbours reservations about Hancock's model. He says fungal biopesticides are hard to assess in the field, as mosquitoes usually become infected in their resting phase and little is known about their resting habits.
"Thus there is no reasonable assessment that can be made on the extent of contact and take up of the pathogen," he says.
PLoS Computational Biology doi 10.1371/journal.pcbi.1000525 (2009)