Evolution in response to vector control
This project addresses two neglected areas in the evolution of infectious disease: the importance of within-vector ecology for transmission, and how parasites may evolve in response to vector control methods. Our view is that anticipating parasite evolution will inform monitoring strategies for current control programs as well as suggest how to prevent clinically unfavourable outcomes of future programs.
Vector control programmes (e.g., large-scale insecticide use) are underway and whilst the evolutionary responses of the vector are being monitored (e.g., insecticide resistance in mosquitoes), the potential evolutionary responses of parasites are largely being ignored. We suspect vector control is changing the selective forces shaping parasites, for example:
- The evolution of insecticide resistance will change vector population genetics and may involve correlated changes to traits important for vector competence (ability to transmit parasites).
- Vector control measures may affect diversity in the age, reproductive status, and body condition of potential vectors that parasites are exposed to, requiring parasites to adapt.
- Competition in genetically mixed infections suppresses co-infecting genotypes.. By reducing parasite prevalence, vector control will decrease the incidence of competition, and the release from suppression may enhance parasite transmission and so, undermine control.
(credit: EviMalar, Jamie Hall, Edward Ross, Wellcome Trust)
What next?
We would like to know how parasite genetic variation and fitness change under alterations in environmental conditions (i.e., the genotype and phenotype of vectors). We would also like to identify trade-offs between parasite traits that underpin transmission. Such constraints among parasite traits may reveal ways to target vector populations that are more difficult for parasites to overcome.