Review Article

The role of biotic factors in the transmission of free-living endohelminth stages

D. W. THIELTGESa1 c1, K. T. JENSENa2 and R. POULINa1

a1 Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand

a2 Marine Ecology, Department of Biological Sciences, University of Aarhus, Finlandsgade 14, DK-8200 Aarhus, Denmark


The transmission success of free-living larval stages of endohelminths is generally modulated by a variety of abiotic and biotic environmental factors. Whereas the role of abiotic factors (including anthropogenic pollutants) has been in focus in numerous studies and summarized in reviews, the role of biotic factors has received much less attention. Here, we review the existing body of literature from the fields of parasitology and ecology and recognize 6 different types of biotic factors with the potential to alter larval transmission processes. We found that experimental studies generally indicate strong effects of biotic factors, and the latter emerge as potentially important, underestimated determinants in the transmission ecology of free-living endohelminth stages. This implies that biodiversity, in general, should have significant effects on parasite transmission and population dynamics. These effects are likely to interact with natural abiotic factors and anthropogenic pollutants. Investigating the interplay of abiotic and biotic factors will not only be crucial for a thorough understanding of parasite transmission processes, but will also be a prerequisite to anticipate the effects of climate and other global changes on helminth parasites and their host communities.

(Received October 05 2007)

(Revised November 04 2007)

(Accepted November 06 2007)

(Online publication January 22 2008)


c1 Corresponding author: Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand. E-mail: