Reappearance of <em>Taenia ovis krabbei</em> muscle cysts in a roe deer (<em>Capreolus capreolus</em>) in Denmark after 60+ years, with a possible role of a grey wolf (<em>Canis lupus</em>) as definitive host
Taenia ovis krabbei has a semi-sylvatic life cycle with carnivore definitive hosts and cervid intermediate hosts. Cervids become infected by foraging on pasture contaminated with the eggs. Larval stages usually develop in heart and skeletal muscles causing pathological changes and severe illness1,2. Meat infected with T. o. krabbei entails no zoonotic risk, but for aesthetic reasons the infected meat is usually discarded3. Here, we report the reappearance of T. o. krabbei in a roe deer in Denmark after more than 60 years. The cysticerci were diagnosed after histology, morphology4 and sequencing of the cox1 gene5. Shortly after this discovery, a wolf died in a nearby locality, and worms of T. o. krabbei were recovered from its intestine. By phylogenetic analysis, the Danish roe deer and wolf isolates were clearly grouped together with other isolates of T. o. krabbei from wolves in Finnoscandinavia. In mainland Europe, T. o. krabbei is primarily a parasite of wolves6,7. The unexpected reappearance of a wolf in Denmark in 2012 after almost two decades of absence could be a mere coincidence, but may also explain the introduction of this parasite along with the wolf. Domestic dogs, on the other hand, could play a role in transmission of T. o. krabbei in the area, but this has yet to be tested. Deer infections with T. o. krabbei were previously reported in the German county that borders Denmark3, and may have spread from there. But it is also possible that deer infections were already present, but unnoticed, in other areas of Denmark. The helminth burden of invading animals is normally expected to decrease8. However, invading wolves can support their establishment in new areas by carrying worms of T. o. krabbei that cause severe illness in native deer that subsequently become prey to the wolves.
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24th International Conference of the World Association for the Advancement of Veterinary Parasitology, 2013