Parasitic worm in char from Linnevatn (Diphyllobothrium ditremum), 2008.
Photo © Steve J. Coulson

Worms

There are three groups of worm on Svalbard. The Annelida, Nematoda and the Platyhelminthes.

ANNELIDA (Segmented worms)

Segmented worm (enchytraeid worm).  There are no true earthworms on Svalbard but these smaller relatives perform a similar function.Earthworms are annelid worms. There are no earthworms on Svalbard but close relatives, the potworms (Enchytraeidae), are often found in large numbers. These look like small white earthworms but few are longer than two or three centimetres. They live anywhere where there is organic soil, feeding on dead plant material and microbes.


NEMATODA (Roundworms)

Many species of Nematoda can be found in Svalbard. Close to 100 species have been identified from the archipelago but the taxonomy is unclear and often identifications remain to be confirmed.  The majority are free living in the soil but parasitic species, either plant or animal, exist.  Two species have been studied in considerable depth, Ostertagia gruhneri Skrjabin, 1929 and Marshallagia marshalli(Ransom, 1907), both intestinal parasites of the Svalbard reindeer. Unusually, M. marshalli is transmitted during the winter, the eggs being deposited on the winter pastures when the reindeer gather to feed along the wind blown ridge tops.


PLATYHELMINTHES (Flatworms)

Parasitic worm in char from Linnevatn (<i>Diphyllobothrium ditremum</i>)One of the few species of invertebrate introduced to Svalbard by man came with the accidental introduction of the Sibling vole (Microtus rossiameridinalis). The invertebrate goes by the name of Echinococcus multilocularis Leuckart, 1863 and has a complicated life cycle involving both the vole and the arctic fox (Alopex lagopus). The parasite is an adult tapeworm in the gut of the fox. These adults produce eggs which pass out of the fox with the faeces and become attached the vegetation. The eggs can now be eaten by the vole while it is grazing on the grasses. Once in the gut of the vole the eggs hatch and the larvae migrate through the gut lining into the blood stream and to the liver. On arrival here they develop into a hydatid cyst, a large mass of tissue that swells and eventually kills the vole. The vole is then scavenged by the fox, eaten and the cysts develops into the adult tapeworm in the gut of the fox and is ready to produce more eggs. The parasite is potentially dangerous to humans since it is possible to become infected with the eggs. The subsequent illness is termed alveolar hydatid disease and is often fatal unless treated early. It is extremely difficult to surgically remove the hydatid cysts and main treatments rely on drugs that prevent development of the parasite. However, infection is rare. First one must ingest the eggs so normal hygiene procedures in known risk areas will reduce the likelihood of infection significantly. Also, in most cases the immune response of the body detects and removes the parasite.

The vole is thought to have been brought to Svalbard with feed for the horses in the now derelict Russian mine at Grumont. Eggs of the parasite may be found where voles and foxes live in closed contact. Voles have established themselves along the coastline from Colesdalen to Adventfjord. It seems unlikely that the vole will be able to spread much further since the vole requires access to vegetation throughout the winter on which it feeds and a deep insulating snow layer to protect against extremes of low temperature. These conditions are found under the bird cliffs but are rare elsewhere. Since the foxes roam over large areas infected foxes may in principle be found almost anywhere but it seems the chances of being infected are low.