ORIGINAL PAPER A. Pawelczyk Æ A. Bajer Æ J. M. Behnke F. S. Gilbert Æ E. Sinski Factors affecting the component community structure of haemoparasites in common voles (Microtus arvalis) from the Mazury Lake District region of Poland Received: 20 July 2003 / Accepted: 15 October 2003 / Published online: 9 January 2004 Ó Springer-Verlag 2004 Abstract The prevalence and abundance of infections with haemoparasites were studied over a 4-year period in Microtus arvalis (common vole, n =321) sampled from fallow grassland sites in north-eastern Poland. Total species richness was five (prevalence= Haemobartonella sp. 63.9%, Bartonella spp. 27.7%, Babesia microti 9.0%, Trypanosoma sp. 8.4% and and Hepatozoon lavieri 3.1%) with 76.9% of the voles carrying at least one species and a mean infracommunity species richness of 1.1. Variation in species richness was determined pri- marily by season and year, the interaction of these fac- tors, and that of year with host age. The observed frequency distribution of infracommunity species rich- ness did not differ from that predicted by a null model, suggesting that there were no marked associations be- tween the species. Analyses of prevalence and abun- dance of infection with each species in turn, revealed that overall the principal causes of variation were tem- poral and seasonal, their interaction, and interactions with intrinsic factors (age and sex), the latter playing only a minor role in their own right. However, the rel- ative importance of these combinations varied and was distinct for each of the species in the study. Prevalence data revealed eight sets of two- and three-way associa- tions between species, mostly dependent to some extent on one of the intrinsic and extrinsic factors in the model. Analysis of quantitative associations suggested two sets of positive two-way interactions, none of which re- mained after controlling for the effect of extrinsic and intrinsic factors on the abundance of each species. These data are discussed in the context of the changing eco- logical profiles in this region of Eastern Europe and, in a wider context, in relation to current understanding of the factors that shape component community structures of haemoparasites in wild rodents. Introduction Wild rodents play an important role in nature as reser- voir hosts for many pathogens, including some that can be transmitted to other animals including humans. Infections with haemoparasites are widespread in wild rodents and are dependent on zoonotic cycles that also involve arthropod vectors. Our understanding of the transmission cycles involved is still incomplete, particu- larly in respect of the key factors that regulate trans- mission. In contrast to helminth communities, haemoparasites of small wild rodents have received rel- atively little attention in Europe and published studies have largely reported on rodent communities in Western and Northern Europe (Baker et al. 1963; Baker 1974; Krampitz 1981; Birtles et al. 1994). In this respect Central and Eastern Europe have been relatively ne- glected, but there is now growing interest in the occur- rence of haemoparasites in wild rodents from Eastern Europe (Karbowiak and Sin´ski 1996a, 1996b; Kar- bowiak et al. 1999) and our earlier studies in the Mazury Lake District region of Poland have drawn attention to the high prevalence of both haemoparasites and Cryp- tosporidium spp. in the dominant woodland rodents of the region (Paweczyk and Sinski 2000; Bajer et al. 2001, 2002). Recently we demonstrated that in woodland and meadow habitats of northern Poland, the rodent species Apodemus flavicollis, Clethrionomys glareolus and Mi- crotus arvalis are important hosts for two groups of parasitic arthropods: fleas and mites, especially imma- ture stages of Ixodes ricinus (Pawelczyk 2003). The level of infestation in small rodents was very high. Fleas A. Pawelczyk Æ A. Bajer Æ E. Sinski Department of Parasitology, Institute of Zoology, University of Warszawa, Miecznikowa 1 Street, 02–096 Warszawa, Poland J. M. Behnke (&) Æ F. S. Gilbert School of Biology, University Park, University of Nottingham, Nottingham, NG7 2RD, UK E-mail: jerzy.behnke@nottingham.ac.uk Tel.: +44-115-9513208 Fax: +44-115-9513252 Parasitol Res (2004) 92: 270–284 DOI 10.1007/s00436-003-1040-1