As often happens on the ProMed-mail list, a news headline and report elicited comment, corrections and more detail from people involved, and then discussion and some argument between experts.In August, a BBC correspondent reported that on the Svalbard islands, Norway, the Svalbard field mouse, Microtus epiroticus, had been found to carry this tapeworm, which can form lethal liver cysts in humans. The only other species of mammal there are the Arctic fox, the Svalbard reindeer (a distinct sub-species) and a population of polar bears; the Arctic fox is the definitive host and rodents the intermediate host of the cestode. Two scientists had ‘tested positive’, one of whom had worked in the area most at risk for only 1 day. The Svalbard administration is offering blood tests to children, people were warned to wash their hands after touching dogs or foxes and to boil water taken from streams and rivers (the Arctic environment was previously regarded as pristine). But no formal warning was issued to tourists. In Longyearbyen, the largest settlement and administrative centre, the huskies or Greenland dogs used for hauling sledges had been tested. The parasite can survive in cats, which are forbidden on Svalbard, though Russians in Barentsburg apparently keep some.The moderator thought cats unlikely to be infective. He believed infectivity for humans to be low, judging from reports of 0.1–1.5 cases per 100 000 people a year in France and Switzerland, where 50% of foxes may be infected (see J. Eckert and P. Deplazes, Alveolar echinococcosis in humans: the current situation in Central Europe and the need for countermeasures. Parasitol. Today 15, 315–319, 1999). He also thought serological testing raised a problem, since on the basis of a study in Japan, a positive test only had a predictive value of 1%. ‘What to tell the remaining 99%? Are they asymptomatic, but infected? Have they been exposed … but are not infected? Should they receive treatment with potential side effects, and if so in which doses and for how long?’ He was challenged by two authorities from Germany, Thomas Romig (University of Stuttgart-Hohenheim) and Peter Kern (University of Ulm): cats can have very heavy infections and may well be transmitters (P. Deplazes et al. Echinococcus multilocularis coproantigen detection by enzyme-linked immunoabsorbent assay in fox, dog, and cat populations. J. Parasitol, 85, 115–121, 1999; D.J. Jenkins and T. Romig, Efficacy of Droncit (R) Spot-on (praziquantel) 4% w/v against immature and mature Echinococcus multilocularis in cats. Int. J. Parasitol. 30, 959–962, 2000). Apart from Japan, there have been population studies in France, Switzerland and Germany and predictive values depend on the specificity of the antigens used. Diagnosis needs to be based on a combination of serology and imaging techniques (ultrasound or CT liver scan), see T. Romig et al. An epidemiologic survey of human alveolar echinococcosis in southwestern Germany. Romerstein Study Group. Am. J. Trop. Med. Hyg. 61, 566–573, 1999.Heikki Henttonen (Finnish Forest Research Institute, Vantaa, Finland), who was one of the scientists in the original report, provided a correction and told us more: there are no native rodents on the Svalbard island group, which is situated in the Arctic Ocean halfway between the North Pole and mainland Norway. [‘The Arctic pearl’ featured in Icelandic texts in 1194, was discovered by Barents in 1596, and its sovereignty was given to Norway in 1925; glaciers cover 60% and Spitzbergen is the largest island, according to its website at www.svalbard.net , which has very pretty pictures.] The sibling vole, Microtus rossiaemeridionalis, was introduced from Eastern Europe and has survived in one place, under cliffs with huge seabird populations that fertilize the grass beneath. In autumn 1999 it was found in dog yards at Longyearbyen, and could thus possible have infected sled dogs there. While the Arctic fox, the main host of E. multilocularis in Svalbard, can migrate long distances, the life cycle of the parasite was not completed in the absence of voles and lemmings. It is not found ‘on the Fennoscandian mainland’ and has only become established in Svalbard after the introduction of sibling voles — ‘an interesting example of how a dangerous parasite can establish itself to a new area after accidental introduction of an intermediate host’. In contrast to the moderator's view, the Norwegian authorities thought that antibody screening would calm the worries of the local people. The probably few positive cases could be studied further.
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Oct 1, 2024
Tomáš Pospiszyl 
Open Access
