The relationship between biodiversity and disease transmission risk

A healthy ecosystem is sustainable, meaning that it has the ability to maintain its structure and functions over time. Past definitions concerning the health of an ecosystem included, among others, both the diversity and complexity of the system, meaning that a healthy ecosystem is a diverse one. In the last decade, researchers have started to focus more on the importance of biodiversity for the distribution and maintenance of diseases in ecosystems, and therefore the ecosystems’ role for human health. Based on a vector-borne model of Lyme disease, it was claimed that with a higher biodiversity of non-reservoir hosts for a pathogen, transmission events and infection risk would become reduced, called the dilution effect. This was further adapted for other vector-borne and nonvector-borne diseases, providing evidence for both the absence and the presence of the dilution effect in the wild. Until now, there is still a large lack of knowledge about the mechanisms driving disease transmission in the wild. The aim of this review is to provide insight into disease systems that were studied in relation to biodiversity and disease transmission risk. Furthermore, we discuss methods and strategies which are necessary to improve our understanding of the impact of biodiversity on disease systems and to help fill the existing gaps in our current knowledge. Keywords: dilution effect, Lyme disease, rescue effect, West Nile virus, hantavirus