Seasonal and annual variations in the prevalence of helminths in a cyclic population of Clethrionomys glareolus

Abstract

Six cestode and two nematode species were recovered from a cyclic population of Clethrionomys glareolus in southern Norway. The cestode Aprostatandrya macrocephala and the nematode Heligmosomum glareoli were euconstant species which displayed late spring/early summer peaks in numbers after which they declined. This decrease in prevalence was correlated with decreasing mean age of the host population. Increases in the prevalence of infections with the nematode Syphacia nigeriana in bank voles were correlated to increasing numbers of Microius agrestis in the mixed woods. Cestode larvae were at maximum prevalence during peak years of bank vole abundance. Pathological conditions such as ascites and peritoneal adhesions, as well as splenic and adrenal hypertrophy, were associated with cestode larvae. There was no general trend of an increase in the prevalence of helminth infection with increasing population density of the bank voles.