Research Article

Heligmosomoides polygyrus reduces infestation of Ixodes ricinus in free-living yellow-necked mice, Apodemus flavicollis

N. FERRARIa1a2 c1, I. M. CATTADORIa3a4, A. RIZZOLIa2 and P. J. HUDSONa4

a1 Dipartimento di Patologia Animale, Igiene e Sanità Pubblica Veterinaria-Università degli Studi di Milano, Via Celoria, 10-20133 Milano, Italy

a2 Centro di Ecologia Alpina, Fondazione Edmund Mach, 38040 Viote del Monte Bondone Trento, Italy

a3 Division of Animal Production and Public Health, Faculty of Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK

a4 Center for Infectious Disease Dynamics, Department of Biology, the Pennsylvania State University, University Park, PA 16802, USA


Free-living animals are usually inhabited by a community of parasitic species that can interact with each other and alter both host susceptibility and parasite transmission. In this study we tested the prediction that an increase in the gastrointestinal nematode Heligmosomoides polygyrus would increase the infestation of the tick Ixodes ricinus, in free-living yellow-necked mice, Apodemus flavicollis. An extensive cross-sectional trapping survey identified a negative relationship between H. polygyrus and I. ricinus counter to the prediction. An experimental reduction of the nematode infection through anthelmintic treatment resulted in an increase in tick infestation, suggesting that this negative association was one of cause and effect. Host characteristics (breeding condition and age) and habitat variables also contributed to affect tick infestation. While these results were counter to the prediction, they still support the hypothesis that interactions between parasite species can shape parasite community dynamics in natural systems. Laboratory models may act differently from natural populations and the mechanism generating the negative association is discussed.

(Received July 22 2008)

(Revised October 04 2008)

(Revised October 24 2008)

(Revised November 19 2008)

(Accepted November 19 2008)

(Online publication January 21 2009)


c1 Corresponding author: Dipartimento di Patologia animale, Igiene e Sanità pubblica veterinaria, Università degli Studi di Milano, Via Celoria 10, 20133 Milano, Italy. Tel: +39 02503 18097. Fax: +39 02503 18095. E-mail: