Shared pathogens can alter the interaction between native and alien species resulting in disease-mediated invasions (DMIs). Invasive species often harbour low-virulence macroparasites, but empirical evidence for macroparasite-driven DMIs is still limited due to their sublethal impacts and scarce prominence. Here we modelled the dynamics of native red squirrels, invasive grey squirrels and their shared nematode Strongyloides robustus to assess whether macroparasites can drive DMIs and lead to native species extinction. Our simulations showed that spillover of the alien parasite can lead to red squirrel extinction, that grey squirrels amplify the infection in the native host and that the infection accelerates the replacement of red squirrels compared to direct competition alone, ultimately facilitating invasion by grey squirrels. These results demonstrate that sublethal macroparasites can mediate invasions, suggesting that we are overlooking key drivers of native species decline.

Animal tuberculosis (TB) is a widespread infectious disease caused by the Mycobacterium tuberculosis bacteria belonging to the Mycobacterium tuberculosis complex (MTC) that can persist in reservoir wildlife hosts. Wild boar (sus scrofa) are a key reservoir for MTC and an increasing trend in wild boar density is expected to lead to an increase in TB prevalence with spill-over to livestock. MTC infection is presently controlled through a variety of strategies, including culling. African swine fever (ASF) is a virulent, viral infection which affects wild boar and is spreading across Eurasia and Oceania. ASF infection leads to near 100% mortality at the individual level, can cause a dramatic decrease in population density and may therefore lead to TB control. In this study we develop a mathematical model to examine the impact of ASF introduction into a wild boar population that supports endemic TB. Our model results indicate that an ASF infection will reduce wild boar population density and lead to a decrease in the prevalence of TB. If ASF persists in the local host population the model predicts the long-term decline of TB prevalence in wild boar. If ASF is eradicated, or fades-out in the local host population, the model predicts a slower recovery of TB prevalence in comparison to wild boar density after an ASF epidemic. This may open a window of opportunity to apply TB management to maintain low TB prevalence.