Modelling the impact of shared pathogens in wildlife communities

Abstract

The thesis uses mathematical modelling to answer important eco-epidemiologial questions in scenarios where interacting species share an infectious disease. These questions are important as shared disease is often linked to successful species invasion and so the disease increases the threat for native species. Shared disease is also linked to spillover and zoonotic infection and so can pose a threat to human health. We develop a model to assess the threat of the shared disease, squirrelpox, carried by the invasive grey squirrel to the conservation of red squirrels in the UK. We show that the grey squirrel epidemiological dynamics include reinfection and partial immunity and that squirrelpox infection levels can be high. This can lead to spillover to red squirrels when the species are sympatric, leading to epidemic outbreaks in red squirrel populations. We analyse general models that examine the role of shared infectious disease on the spatial spread of invasive species and the replacement of native species. We show that shared infectious disease can increase the rate of replacement of a native species even when the disease is not supported in the native species system. We develop a model for a prey, specialist predator, and generalist predator system in which the predators can become infected through consumption of infected prey and can transmit infection back to the prey species. The analysis shows that predators can increase the persistence of infectious disease and may act as epidemic bridges that support the infection during low density phases in the prey species.