Project Title: (PEMC)Population-stabilizing portfolio effects of fine-scale environmental variations in natural resource availability to malaria vector mosquitoes; Characterization and implications for malaria vector control strategies
Project Description: Since the turn of the century, over 4 million malaria-related deaths have been averted in Africa, mostly through vector control using bed nets treated with exceptionally safe and affordable pyrethroid insecticides. However, progress has stalled because resistance of mosquitoes to insecticides has eroded the impact of insecticide-treated nets, and because mosquitoes can avoid them by feeding upon animals, feeding outdoors or resting outdoors. Furthermore, vector mosquitoes often exhibit remarkable phenotypic plasticity in all the important... Since the turn of the century, over 4 million malaria-related deaths have been averted in Africa, mostly through vector control using bed nets treated with exceptionally safe and affordable pyrethroid insecticides. However, progress has stalled because resistance of mosquitoes to insecticides has eroded the impact of insecticide-treated nets, and because mosquitoes can avoid them by feeding upon animals, feeding outdoors or resting outdoors. Furthermore, vector mosquitoes often exhibit remarkable phenotypic plasticity in all the important host-seeking, resting and oviposition behaviours that could be targeted with additional interventions, making it difficult to select any single supplementary measure to achieve malaria elimination. Such variations in mosquito resource utilization behaviours are driven by environmental heterogeneities in the availabilities of resources like blood hosts, resting sites and oviposition sites, making malaria vectors a moving target for even the most astute control practitioner. This behavioural diversification phenomenon fits squarely within conceptual framework for portfolio effects recently adopted from economics by conservation biologists. In simple terms, diversification stabilizes investment portfolios by statistical averaging of individual asset dynamics that often correlate weakly or negatively with each other. The same simple probability theory applies equally well to complex ecosystems, which are buffered against perturbations by biological and environmental diversity. In collaboration with a colleague at my proposed host institution, I recently extended this conceptual framework to mosquitoes and malaria transmission in the context of behaviourally-targeted vector control interventions. Vector biodiversity and behavioural plasticity interact with environmental resource distribution heterogeneities to create portfolio effects that bolster them against vector control interventions by diversifying expression of targetable behaviours. However, portfolio effects could also create refugia for mosquitoes against insecticide pressure and possibly enable back-selection for desirable susceptibility traits. Here I propose to demonstrate how fine-scale spatial and temporal heterogeneities in mosquito resource availability cause such large behavioural variations that malaria elimination will necessitate continuous blanket coverage with complementary vector control interventions targeting all extremes of phenotypic plasticity. However, I also aim to demonstrate that portfolio effects arising from wildlife conservation support refugia populations of pyrethroid- susceptible malaria vectors, which could spread back into nearby human-settled areas if astute insecticide combinations were deployed to favour their survival there. I will also assess whether beneficial observer effects of participation in this health ecology research programme can bolster conservation in a Wildlife Management Area, to expand wild bovid populations and enhance dispersal of pyrethroid-susceptible traits into domestic malaria vector populations.
Principal Investigator : Gerry Killeen
Department Name : EHES
Time frame: (2020-01-01) - (2024-12-31)
AXA Research Fund (Normal)
University College Cork (UCC) (Normal)
External Collaborating Partners
Institut de Recherche pour le Développement (IRD)