Fox tapeworms are parasites that live at the expense of their intermediate hosts and primary hosts, nesting in their tissues. The endoparasites primarily use rodents as intermediate hosts, weaken them, and, along with the animal, are ingested by larger mammals such as foxes. For humans, fox tapeworm infection is often fatal if untreated.
What are fox tapeworms?
The fox tapeworm is also known as Echinococcus multilocularis. It is a parasitic life form of the tapeworm class. Systematically, it belongs to the subclass of true tapeworms or Eucestoda, among which it belongs to the order Cyclophyllidea and family Taeniidae. The species belongs to the tapeworm genus Echinococcus and thus corresponds to an endoparasite from the group Cestoda. Echinococcus multilocularis grows up to three millimeters long and consists of up to five tapeworm limbs, so-called proglottids. In the head area, fox tapeworms carry four suckers and a hook. This allows them to attach to the intestinal wall of their hosts. The hooks are arranged in circles around the sucker and form groups of up to 18 hooks up to 34 micrometers long. The fox tapeworm is widespread only in the northern hemisphere, especially in Germany, Switzerland and eastern parts of France. The fox tapeworm depends for its distribution on suitable hosts and intermediate hosts, which are found only in temperate to cold-temperate climates of the northern hemisphere. Parasites always harm their hosts. Thus, infestation with Echinococcus multilocularis must necessarily be considered pathogenic.
Occurrence, distribution, and characteristics
Like all endoparasites, the fox tapeworm feeds at the expense of the host organism. It absorbs nutrients directly through its body surface. The fox tapeworm does not possess an intestine. Mice and small animals act as intermediate hosts. The main hosts are larger mammals, especially the fox and the dog. Fox tapeworms spend their lives within the small intestine of definitive hosts. Their eggs mature in their reproductive limb. Once the reproductive limb is shed, the first larval stage of the next generation is complete. The eggs travel along the intestinal tract of the host and are excreted by the host. A fox tapeworm produces up to 200 eggs per day. The excreted eggs remain infectious for months under the most adverse climatic conditions. Intermediate hosts such as rodents reabsorb the eggs. During this process, the larval capsule dissolves and oncospheres, called hexacanth larvae, are released. These larvae pass through the intestinal mucosa of the intermediate host to enter the bloodstream. They travel through the bloodstream to the liver of the intermediate host or infect the lungs, heart and spleen. The oncospheres thus settle in the tissues of the organs, where they pass into the larval stage of metacestodes or fins. Thanks to the formation of gelatinous bubbles, they are separated from the host tissue. From the metacestode wall, further fins bud off piece by piece and infiltrate the tissue. Like metastases, they migrate via the bloodstream to other organs. In the third larval stage, protoscolices with head plant invaginations are formed. The intermediate host becomes so weak from infection that it is easy prey for potential final hosts such as the fox, dog, or cat. Even after the death of the intermediate host, the larvae remain infectious in the carcass and thus can spread as a carrion infection. The protoscolices are released from the intermediate host tissues in the digestive tract of the definitive host and grow into adult worms in the small intestine of the primary host. Humans most commonly become infected with fox tapeworm through contaminated mushrooms and wild berries. Smear infections after contact with forest soil are also a source of infection. Dogs, foxes, and cats can also infect humans through contact with barely noticeable droppings.
Diseases and ailments
In humans, fox tapeworm causes alveolar echinococcosis. The infectious disease is manifested by characteristic cyst formation in the body. Typically, fox tapeworm cysts grow in an invasive manner, that is, they invade the tissues of organs. They are usually the size of a hazelnut and grow in clusters. The cysts are surrounded by connective tissue and granulation tissue and are interconnected. Due to the cyst formation, the infection destroys the affected organ piece by piece.In many cases, the infection spreads further in the body by metastasis and, over time, affects organs further away. The clinical signs are similar to those of carcinoma. Depending on the organs affected, the individual symptoms may vary from case to case. Organic functional impairments of all kinds may occur. Therapy is absolutely necessary to improve the prognosis. Optimally, all Echinococcus cysts are surgically removed. However, because the cysts infiltrate the tissue, chemotherapy with albendazole or mebendazole is given in most cases. Specific drugs against the tapeworm species do not exist. Prophylaxis plays the most important role in the context of fox tapeworm infection. At temperatures of 70 degrees Celsius, the larvae of the fox tapeworm die. Therefore, canning food is a suitable prophylaxis. Offal and raw meat for dog and cat food can be cooked through, and pets can be dewormed regularly. Wild fruits and mushrooms are ideally washed thoroughly and heated sufficiently before consumption. Immunocompromised patients are at greater risk of contracting fox tapeworm.
