Echinococcus multilocularis, or fox tapeworm, is a tapeworm whose intermediate host is the vole. Adult-stage tapeworms live in the small intestine of canines. This is why the parasite is known as the fox tapeworm in everyday language. The parasite larvae cause a tumour-like and rapidly growing cluster of cysts to develop in the liver of the vole serving as the intermediate host. Dogs are infected by eating a vole with parasites.
The spread of this parasite should be prevented because humans may also develop similar but slow-growing larval cysts in their livers if they swallow the faeces of a canine animal. Although humans are aberrant hosts for the parasite, the infection is life-threatening and requires lifelong medication. It is likely that humans are usually infected by food contaminated with eggs, including vegetables and possibly berries, or they get the eggs on their hands and, consequently, mouth from the fur of an infected dog.
Occurrence
It is assumed that only a small proportion of infected people fall ill and that the human immune defence system kills the parasite in most cases. In Switzerland, for example, where the parasite is widespread in the fox population (15% to 20%), approx. 0.2 people out of 100,000 (0.0002%) fall ill every year. Thanks to medical treatment, they can live more or less normal lives. In Sweden, where a small number of Echinococcus cases occur, the authorities have still held off recommending that wild berries should be washed or cooked before eating.
In the wild, the most important primary host of the parasite (the animal in whose intestine the adult-stage worms live as parasites) is the fox. The dog is the only pet that can become a significant primary host. In cats, infections have been diagnosed on rare occasions, and in experimental studies, cats have not been found to produce live infectious eggs. No infections are known to have been reported in ferrets.
In a study carried out some 15 years ago, echinococcus-infected foxes were found in the westernmost parts of Ukraine but not elsewhere in the country. Since then, the parasite may have expanded its range in Ukraine, as it has previously also done elsewhere in Europe. No published data can be found on echinococcus infections in Ukrainian dogs, but it should be assumed that dogs arriving in Finland from Ukraine may be carriers. Echinococcus infections have never been diagnosed in Finland.
Treatment and prevention
In experiments, dogs have produced eggs for at least three months after being infected, but presumably egg excretion stops within six months at the latest once the worms have died of old age. Treating dogs with a dewormer that is effective against echinococcus (praziquantel) efficiently eradicates the tapeworm. Unless the dog is constipated, its faeces no longer contain tapeworms or eggs 24 hours after the dewormer has been administered.
Ukrainian refugees’ dogs are treated against echinococcus at the border, and their owners are instructed to collect the dogs’ faeces in plastic bags and dispose of them with mixed waste. If this has not happened for one reason or another, an appointment with a veterinarian should be made for the pet as soon as possible. The veterinarian will treat the pet on the Finnish government's account. When booking an appointment, you should mention that the dog has come from Ukraine. Normally, dogs should be treated one to five days before arriving in Finland.