Epidemiology and evolution of vector borne disease

• Main Author: Harrison, Eleanor Margaret
• Other Authors: Adams, Ben
• Published: University of Bath 2013
• Subjects: 614.43
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619145

In recent years the incidence of many vector borne-diseases has increased worldwide. We investigate the epidemiology and evolution of vector-borne disease, focussing on the neglected tropical disease leishmaniasis to determine suitable strategies for control and prevention. We develop a compartmental mathematical model for leishmaniasis, and examine the dependence of disease spread on model parameters. We perform an elasticity analysis to establish the relative impact of disease parameters and pathways on infection spread and prevalence. We then use optimal control theory to determine optimal vaccination and spraying strategies for leishmaniasis, and assess the dependence of control on disease relapse. We investigate the evolution of virulence in vector-borne disease using adaptive dynamics and both non-spatial and metapopulation models for disease spread. Using our metapopulation model we also determine the impact of land-use change such as urbanisation and deforestation on disease spread and prevalence. We find that in the absence of evolution, control techniques which directly reduce the rate of vector transmission lead to the greatest reduction in potential disease spread. Although the spraying of insecticide can reduce the basic reproductive number $R_{0}$, we find that vaccination is more effective. Disease relapse is the driving force behind infection at endemic equilibrium and greatly increases the level of control required to prevent a disease epidemic. When a trade-off is in place between transmission and virulence we find that control techniques which reduce the duration of transmission lead to the fixation of pathogen strains with heightened virulence. Control techniques such as spraying can therefore be counterproductive, as increasing virulence increases human infection prevalence. This holds true when virulence is in either the host or vector and suggests that virulence within the vector should not be ignored. Urbanisation and deforestation can also lead to increases in both transmission and virulence, as reducing the distance between urban settlements and the vector natural habitat alters disease incidence.