The role of vole populations in prevalence of the parasite (Echinococcus multilocularis) in foxes |
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Authors: | Takashi Saitoh and Kenichi Takahashi |
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Institution: | (1) Hokkaido Research Center Forestry and Forest Products Research Institute, 062-8516 Sapporo, Japan;(2) Hokkiado Institute of Public Health, Kita 19, Nishi 12, 060-0819 Sapporo, Japan |
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Abstract: | Effects of population fluctuation of the gray-sided vole(Clethrionomys rufocanus) on the prevalence (infection rates) of the parasiteEchinococcus 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 carry over 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. |
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Keywords: | Clethrionomys rufocanus density-dependence functional response numerical response Vulpes vulpes |
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