What is "fox disease" ?
“Fox disease” is the common name for a parasitic disease caused by Echinococcus multilocularis, a flatworm that lives in the intestines of foxes but also dogs and cats.
While this parasitosis generally causes no symptoms in our pets, it can accidentally be transmitted to humans in whom it causes a very serious and potentially fatal disease.
How is alveolar echinococcosis transmitted?
E. multilocularis, the parasite in question
E.multilocularis is a cestode, in other words a very small flatworm (about 5mm) that lives in the intestines of dogs, cats or foxes, their definitive hosts.They attach themselves to the intestinal mucosa of the animals they infest through their scolex, their anterior part provided with circular suckers and dagger-like hooks. These worms also have 3 to 4 segments including a single ovigerous segment which contains many eggs.
Understanding the life cycle of E.multilocularis
The life cycle of E.multilocularis takes place between an intermediate host and a definitive host.
The intermediate hosts of the parasite are generally voles and rodents which become contaminated by ingesting water or food soiled by the droppings of infested foxes or dogs, which contain the eggs of the parasite. Once in the rodent's stomach, the eggs are digested and release parasite larvae, which are able to cross the wall of their intestines and migrate via the bloodstream to the liver where the larva develops. Multiple vesicles are then formed in this organ, each containing a large quantity of parasites.
The definitive hosts of the worm are dogs, foxes and cats. They harbor the worms within their intestines where the parasites feed on their intestinal contents. The worms then release their ovigerous segments in the animal's stool. Once in the external environment, the eggs then release the larvae they contain.
The worm's definitive hosts are most often contaminated by ingesting infested rodents or by consuming water or food soiled by the excrement of other contaminated animals. Very often, it is wild berries (blackberries, wild strawberries) located at ground level that are the source of contamination. For these reasons, it is most often hunting dogs and/or dogs that roam in places where foxes live in risk areas that are most at risk of being parasitized.
Human beings, an accidental intermediate host of the worm
Humans can, like rodents, act as an intermediate host for the worm. He can become contaminated by consuming berries or herbs soiled by the excrement of infested animals, by gardening in a risk area or during contact with his dog or cat if the latter is a carrier of the parasite. Like the rodent, it will undergo the development of the larva in its organs.
Regions at risk
E.multilocularis is a worm present in the northern hemisphere and in particular in Europe (especially France, Germany, Belgium, Switzerland and Italy), China, Russia and North America.
In France, the worm is present in the North East quarter of the country, from the Ardennes to the Alps. Recently, the presence of the parasite is progressing towards the West and reaches the Paris region, Ille-et-Vilaine as well as Upper Normandy.
What are the symptoms in dogs?
This parasitosis is unique in that it goes completely unnoticed in dogs and cats. In our pets, E.multilocularis infestations are almost always asymptomatic.
On the other hand, an infestation in humans is responsible for a very serious disease called alveolar echinococcosis. The disease is responsible for the formation of a tumor in the liver which gradually destroys the organ and whose signs can appear up to several years after the ingestion of the eggs of the parasite. Symptoms consist of abdominal pain, jaundice and an enlarged liver. The development of the tumor can reach other organs such as the lungs or the brain.
How to prevent E.multilocularis infestations?
Above all else, it is essential to regularly deworm all pets that live in high-risk areas and all the more so if these animals go out into the forest or the countryside (hunting dogs, sheepdogs ).Ask your veterinarian for advice on using an effective dewormer against this cestode.
Wash your hands systematically after petting your pet or after your dog has licked you.
Wherever possible, avoid your pet consuming wild rodents and/or potentially contaminated berries.
Note!
Worm eggs are extremely resistant in the external environment. If eggs are present on fruit, neither a simple rinsing with water nor freezing will sanitize them. Unless you cook them, avoid eating them or letting your pet eat them.