Veterinærinstituttet har fått midler til et prosjekt om revens dvergbendelorm
The tiny but formidable dwarf fox tapeworm, Echinococcus multilocularis, has been lurking in Svalbard’s wildlife for decades. First discovered in voles, and later in Arctic foxes, near Grumantbyen and Fuglefjella at the end of the last century, this parasite has a complex life cycle that allows it to persist in the harsh Arctic environment. Measuring only about 4mm long, this tapeworm resides in the small intestines of wild and domestic canines, such as foxes and dogs. Infected hosts shed the parasite’s eggs through their faeces, into the environment where they can be ingested by rodent intermediate hosts. Once inside a rodent, the parasite forms large cysts in the liver, and sometimes the lungs, before completing its cycle when a canine predator eats the infected rodent. Unfortunately, humans can also fall victim to this parasite. If infected with eggs from wild or domestic canines, people can develop alveolar echinococcosis, a serious disease characterized by slow-growing parasitic cysts in the liver. Without treatment, infection can be fatal.
Investigating the Risk in Svalbard
Despite its potential health risks, there is no routine surveillance of Echinococcus multilocularis in Svalbard’s foxes or voles. However, multiple independent research projects have monitored its presence in different hosts. This report compiles the findings from three of the most recent studies, offering insights into how the parasite’s prevalence might be shifting in the high Arctic.
Researchers analysed faecal samples from 700 Arctic foxes trapped for their fur between 2009 and 2023, using sensitive molecular techniques to detect the parasite. The overall infection rate was relatively low, at 4.4%, though prevalence was slightly higher in the core vole habitat near Grumant and Fuglefjella. Among 380 foxes examined in more detail, the intensity of infection in the intestine varied widely, from as few as nine adult tapeworms to over 80,000. Given that each tapeworm produces hundreds of eggs, and infections can persist for at least a month, the environmental contamination risk from fox faeces is significant. Infected foxes were detected throughout the archipelago and not just in close proximity to the core vole distribution area.
What About Voles and Domestic Dogs?
Between 2016 and 2021, researchers examined 157 rodents, primarily Eastern European voles caught in and around Longyearbyen, along with a single house mouse from Barentsburg. Encouragingly, none of these rodents tested positive for Echinococcus multilocularis on post-mortem examination.
Similarly, molecular analysis of faecal samples from 404 domestic dogs in Svalbard (collected in 2016-2017 and 2021) found no trace of the parasite. Only one dog tested positive for a different tapeworm, Taenia krabbei, which cycles between canines and reindeer but poses no risk to humans. This highlights the importance of ensuring that meat or offal fed to dogs is sufficiently cooked to inactivate any parasitic cysts. Most dog owners reported deworming their pets at least twice a year.
Assessing the Risk for Humans
The risk of infection near human settlements is currently low, especially with regular deworming of dogs. To stay safe, dogs should avoid eating rodents or spending time in the core vole habitat around Grumant. For most dogs, deworming twice a year is enough, but those with higher exposure may need monthly treatment during peak risk periods. People visiting or living in Svalbard should also take precautions, avoid drinking untreated surface water, especially around Grumantbyen and Fuglefjella, and always wash hands before eating to prevent accidental ingestion of parasite eggs.
However, climate change is gradually expanding vole populations in Svalbard, potentially altering the dynamics of parasite transmission. If vole numbers establish closer to human settlements, the chance of transmission to domestic dogs, and potentially humans, will rise. Continued surveillance of Echinococcus multilocularis in foxes and voles, especially near human settlements, will be essential in ensuring this parasite doesn’t become a bigger threat in the future.