The role of vole populations in prevalence of the parasite (Echinococcus multilocularis) in foxes

Abstract

Abstract. Effects of population fluctuation of the gray-sided vole (Clethrionomys rufocanus) on the prevalence (infection rates) of the parasite Echinococcus multilocularis in red fox (Vulpes vulpes)populations was investigated from 1985 to 1992 in eastern Hokkaido (Abashiri, Nemuro, and Kushiro area), Japan. This parasite needs two hosts to complete its life cycle; the gray-sided vole as its intermediate host and the red fox as its final host. We found that: (1) Infection rates in foxes depended on the current-year abundance of voles in all three study areas, particularly in Abashiri. (2) In addition to this direct density-dependence, delayed density-dependence between the infection rate and the prior-year abundance of voles was detected in Nemuro and in Kushiro. (3) The regional differences in density-dependence pattern were related to regional differences in the winter food habits of red foxes: in Abashiri the proportion of voles in the fox's diet greatly decreases in winter, while the proportion remains high in winter in Nemuro and in Kushiro, probably because of shallower snowpack. These results suggest that infection rates in foxes in Abashiri were less influenced by the prior-year prevalence, since the infection cycle might be interrupted in winter, when voles became less important in fox's diet. In contrast, the state of the prevalence may carryover from year to year in Nemuro and in Kushiro, because red foxes continue to eat a considerable amount of voles throughout year. The regionally contrasted results for the relationship between infection rate in foxes and vole abundance were parallel to the regional difference in fluctuation pattern of vole populations, which are highly variable in Abashiri area, but less variable in Kushiro-Nemuro area. Drastic change in vole populations appears to affect the host-parasite system.

A model for the transmission of Echinococcus multilocularis in Hokkaido, Japan

“…A difference in the prevalence rate between Nemuro and Abashiri was also indicated by the field data (Table 1; Saitoh and Takahashi, 1998); the simulation showed that this was caused by a difference in snowfall between the two provinces.…”

Trophic ecology, behaviour and host population dynamics in Echinococcus multilocularis transmission

“…An early major contribution to the transmission ecology of E. multilocularis between small mammals and foxes was given by Saitoh and Takahashi (1998). They investigated E. multilocularis winter prevalence dynamics in a sample of 9828 foxes (V. vulpes) and Myodes rufocanus population variations in three localities of Hokkaido, the northernmost island of Japan, over 8 years.…”

“…The existence of at least two density-dependent mechanisms acting on the control of the parasite transmission dynamics is described: one is based on the variations in the availability of resources including intermediate hosts (Rausch, 1995;Saitoh and Takahashi, 1998;Miterpakova et al, 2006;Tanner et al, 2006;Hegglin et al, 2007;Guislain et al, 2008;Robardet et al, 2008;Raoul et al, 2010;Stien et al, 2010;Wang et al, 2010;Liccioli et al, 2014), and the other is based on the variations in the density of the definitive host and in their faeces distribution (Ewald, 1993;Raoul et al, 2003;Guislain et al, 2007;Wang et al, 2010). However, we are clearly missing data to predict under which conditions the control of E. multilocularis transmission switches from being dominated by intermediate host density to being dominated by definitive host density, and vice-versa, in space and/or in time.…”

“…However, we are clearly missing data to predict under which conditions the control of E. multilocularis transmission switches from being dominated by intermediate host density to being dominated by definitive host density, and vice-versa, in space and/or in time. Additionally, the importance of considering non-linearity and both the direct and delayed response of definitive hosts contamination in relation to intermediate host population variations was noted in eastern France and Japan, respectively (Saitoh and Takahashi, 1998;Raoul et al, 2010).…”

So, what do we know and what do we need to know more about the population ecology of the voleClethrionomys rufocanus?

“…et al 1998). Saitoh and Takahashi (1998) demonstrated a close relation between C. rufocanus and foxes through the infection rate of the parasite Echinococcus multilocularis in the field.…”