Interacting parasites

Abstract

Parasitism is the most popular life-style on Earth, and many vertebrates host more than one kind of parasite at a time. A common assumption is that parasite species rarely interact, because they often exploit different tissues in a host, and this use of discrete resources limits competition ( 1 ). On page 243 of this issue, however, Telfer et al. ( 2 ) provide a convincing case of a highly interactive parasite community in voles, and show how infection with one parasite can affect susceptibility to others. If some human parasites are equally interactive, our current, disease-by-disease approach to modeling and treating infectious diseases is inadequate ( 3 ). Telfer et al. 's study—which involved tracking infections of four different parasites by taking blood samples from nearly 6000 wild voles ( Microtus agrestis ) over 5 years—helps highlight our growing understanding of how parasites can interact in complex ways (see the figure). What are some of the take-home messages?