Prevalence of coccidia parasites (Protozoa) in red squirrels ( Sciurus vulgaris): effects of host phenotype and environmental factors

Abstract

We investigated the relative importance of environmental factors versus host phenotype in determining parasite prevalence in Eurasian red squirrels (Sciurus vulgaris). One hundred and forty-three fecal samples of 116 different squirrels collected in 2000 and 2001 from five study areas in the Italian Alps, were examined for intestinal protozoans. Two species of Eimeria were present with a medium to high prevalence in both years and in all areas, while two other species were rare, occurring only in some areas and not in all years. Cryptosporidium parvum had a high prevalence in the two study areas of the Western Alps, while in the three areas of the Central Alps it was recorded only once. The prevalence of Eimeria sciurorum and C. parvum fluctuated in parallel with squirrel density, suggesting a possible correlation between the presence of these protozoans and host density. A gender effect on E. sciurorum prevalence at low density could be explained by different space use patterns and social organization of males and females. C. parvum occurred more frequently in young squirrels, suggesting an acquired immunity in adults, but age-related susceptibility was not found for eimerian species. The coccidian community was more similar within than between regions, and study area and year were key parameters in predicting coccidia infection. There was no evidence of competition between coccidian species, but one positive interaction between E. sciurorum and E. andrewsi was observed. Our results suggest that the effects of geographic region, area features, and year effects probably related to fluctuations in host population density, were more important than individual phenotypic host characteristics in structuring the coccidian assemblage and determining levels of parasite prevalence in red squirrel populations.

Natural infection with two genotypes of Cryptosporidium in red squirrels (Sciurus vulgaris) in Italy

“…The prevalence of Cryptosporidium in red squirrels recorded in this study (24.3%) is similar to the values reported by Bertolino et al (2003) for the same areas in previous years (2000-2001: 19.2-27.3%), except for a peak at Rhemes in 2000 (63.6%). However, in three other areas in the Central Alps, Cryptosporidium was recorded only once in 59 animals examined (Bertolino et al 2003).…”

“…We monitored red squirrels in two study areas in the Cogne and Rhemes Valleys, located 21 km apart but within a continuous belt of mature secondary subalpine conifer forests of the Gran Paradiso National Park, Western Italian Alps. Cryptosporidium was previously detected in red squirrels by Bertolino et al (2003) in these two localities. Squirrel densities in the study areas in the years 2000 to 2005 ranged from 0.20 to 0.42 ind./ha at Rhemes and between 0.18 FOLIA PARASITOLOGICA 55: 95-99, 2008 and 0.45 ind./ha at Cogne (Bertolino et al 2003, Wauters et al 2007).…”

“…However, in three other areas in the Central Alps, Cryptosporidium was recorded only once in 59 animals examined (Bertolino et al 2003). Very recently, Feng et al (2007) reported seven different genotypes in sciurid rodents from the New York region, with prevalence reaching 37.5%.…”

“…So far, squirrels were reported to be susceptible to several Cryptosporidium species/genotypes of various host specificities and oocyst morphologies (Matsui et al 2000, Atwill et al 2001, Bertolino et al 2003, Hůrková et al 2003, Feng et al 2007). In 17 separate cases of infection, we found two intestinal Cryptosporidium genotypes that had not been previously observed in red squirrels.…”

“…Recent studies have shown that natural cryptosporidiosis in the family Sciuridae could be caused by various species and genotypes of both gastric and intestinal Cryptosporidium (Matsui et al 2000, Perz and Blancq 2001, Bertolino et al 2003, Hůrková et al 2003, Atwill et al 2004, Feng et al 2007. The presence of Cryptosporidium in red squirrels (Sciurus vulgaris L.) was previously reported from populations in the Western Italian Alps; however, the genotypes of these Cryptosporidium were not investigated Canestri-Trotti 2001, Bertolino et al 2003).…”