Biodiversity Does Not Reduce Transmission of Disease from Animals to Humans, Researchers Find
Mar. 20, 2013 — More than three quarters of new, emerging or re-emerging human diseases are caused by pathogens from animals, according to the World Health Organization.
But a widely accepted theory of risk reduction for these pathogens — one of the most important ideas in disease ecology — is likely wrong, according to a new study co-authored by Stanford Woods Institute for the Environment Senior Fellow James Holland Jones and former Woods-affiliated ecologist Dan Salkeld.
The dilution effect theorizes that disease risk for humans decreases as the variety of species in an area increases. For example, it postulates that a tick has a higher chance of infecting a human with Lyme disease if the tick has previously had few animal host options beyond white-footed mice, which are carriers of Lyme disease-causing bacteria.
If many other animal hosts had been available to the tick, the tick’s likelihood of being infected and spreading that infection to a human host would go down, according to the theory.