Small fox tapeworm
Echinococcus multilocularis, Echinococcus granulosus
Echinococcosis is a disease caused by larvae of the tapeworm genus Echinococcus. In Europe, the small or five-limbed fox tapeworm, Echinococcus(E.) multilocularis, the causative agent of alveolar echinococcosis, and the three-limbed dog tapeworm, E. granulosus, the causative agent of cystic echinococcosis, occur.
The small fox tapeworm occurs in numerous European countries, but especially in Austria, Germany, Switzerland and France. In Bavaria and northern Tyrol, it can be detected on average in every third to fourth fox, and in Vorarlberg in almost every second fox. The United Kingdom, Norway, Finland, Malta and Ireland are officially recognized free of the small fox tapeworm. The dog tapeworm is present worldwide, with an accumulation in Eastern Europe, the Mediterranean region and the Balkan states. In Austria, the dog tapeworm is considered extinct.
Small fox tapeworm: The 2-3 mm small five-limbed worms live in the small intestine of foxes, rarely of cats and dogs. Every one to two weeks, they lace off the last tapeworm limb, which contains about 500 eggs and is released into the environment with the feces. If these tapeworm eggs are ingested by suitable intermediate hosts (e.g., small rodents such as mice) when they are eaten, the eggs develop into larvae, which pass through the intestinal mucosa into the blood and on to the organs, especially the liver, where infective tapeworm heads, known as scolices, are formed. If a person - humans represent a false intermediate host for these parasites - inadvertently ingests these microsopically small eggs, the larvae can develop and infiltrate the liver tissue, like a malignant tumor, called alveolar cysts. The clinical picture is called alveolar echinococcosis.
Dog tapeworm: The 3-6 mm adult worms live in the small intestine of dogs. Every one to two weeks, they lace off the last tapeworm limb, containing up to 1,500 eggs, which is released into the environment with the feces. These tapeworm limbs or eggs are ingested by intermediate hosts (sheep, goats, cattle, pigs) while grazing. The eggs develop into larvae, which pass through the intestinal mucosa into the blood and on to the liver and other organs (e.g., lungs, heart, spleen), where they grow into vesicular formations called fins, or cysts. Within these cysts, thousands of "heads" are formed, each of which can develop into new tapeworms as soon as tissue containing cysts is eaten by a dog. In humans, as in intermediate hosts, the clinical picture is called cystic echinococcosis. Humans become infected via dirt and smear infection by ingesting Echinococcus eggs from fox or dog feces.
Alveolar echinococcosis: The most common symptoms are pain in the upper abdomen and jaundice, occasionally fatigue, weight loss or an enlarged liver caused by cancerous growth of the parasite tissue.
Cystic echinococcosis: Frequent pain in the right upper abdomen due to encapsulated cysts up to 30 cm in size in the liver. The less common infestation of the lungs is characterized by difficulty breathing and coughing.
The goal of treatment is complete surgical removal of the Echinococcus cysts, but this is usually impossible or almost impossible at an advanced stage. Therefore, treatment involves a combination of surgery and administration of antihelminthic chemotherapy.
Cystic echinococcosis: PAIR technique is also available for therapy: ultrasound controlled puncture (P), aspiration (A), instillation (I) of worm head killing substances and reaspiration (R) of cyst contents, together with antihelminthic therapy.
Echinococcus eggs have a relatively high resistance to cold and can thus remain infective for many months. However, dryness and high temperatures kill them within a short time.
To avoid infection with E. multilocularis, hands should be washed thoroughly after working with soil and grass in the garden. Properly deworm dogs that hunt mice more often during the year. Also maintain proper hand hygiene when in contact with dogs. Wash or, if possible, boil food that grows near the ground (e.g. vegetables, mushrooms, berries or fallen fruit) thoroughly before eating. Use gloves when coming into contact with dead foxes or fox droppings.
To avoid infection with E. granulosus, dogs should be dewormed regularly and should not be fed offal from infested sheep.
Lesser fox tapeworm: The lesser fox tapeworm is primarily a tapeworm of the fox (also golden jackal, raccoon dog and wolf), less commonly of the dog and cat, with various species of mice (field mouse, red-backed vole, water vole, water vole), muskrat and other small mammals as intermediate hosts. The adult tapeworms, up to 4 mm long, live between the intestinal villi of the small intestinal mucosa of foxes and feed on the semi-digested food of their host. Several thousand E. multilocularis specimens may be found in the small intestine of a highly infected fox. Despite this large number of parasites, an infested fox is not visibly ill. The last tapeworm limb, typically 5 limbs, may contain several hundred infectious eggs, which are released into the outside world with the fox's feces. If these microscopic eggs are ingested by intermediate hosts (usually mice) in the course of feeding, small larvae hatch in the rodent's intestine, penetrate the intestinal wall, and travel through the bloodstream to the liver. In these highly susceptible intermediate hosts, fluid-filled blisters (tapeworm fins) with numerous tapeworm head systems develop in the liver. The infested mouse becomes diseased within a few weeks, becomes sluggish and an easy prey for the fox. If the infected intermediate host is now preyed upon by the final host fox, a new tapeworm generation develops in it, which can produce eggs capable of infection after only 4 weeks. The transmission cycle is completed as soon as these mature eggs are excreted in the feces of the final host. Egg excretion may continue for several months. In the outside world, eggs of E. multilocularis survive for 2-3 months during the summer in Central Europe if there is sufficient moisture, and up to 8 months in cooler seasons.
Of importance is the small fox tapeworm not primarily for the fox, but for humans, who represent a false intermediate host in the development cycle of the parasite. Due to the unintentional ingestion of these microscopically small eggs, organ-destroying, parasitic tissue usually develops in the liver of infected persons. As a result of dissemination of detached cell clusters via the bloodstream, distant metastases may occur, e.g. in the lungs or brain, similar to a malignant tumor. From the time of infection until the first symptoms appear, 5-15 years may pass. In humans, the disease is called alveolar echinococcosis, occurs predominantly in older individuals, and manifests with symptoms similar to those of liver cancer.
In 2022, 27 hunted foxes in the eastern provinces including Vienna were examined for infection with E. multilocularis; three animals were identified as carriers of these parasites (University of Veterinary Medicine Vienna, Institute of Wildlife Science). Small fox tapeworm was also detected in 46 of 201 examined foxes from Carinthia (NRL Echinococcus, AGES Institute for Veterinary Investigations Innsbruck).
Three-limbed dog tapeworm: The 3-6 mm large adult worms live in the small intestinal mucosa of dogs or other carnivores. Every one to two weeks, they lace off the last tapeworm limb, containing up to 1,500 eggs, which is released into the environment with the feces. These tapeworm members are ingested by intermediate hosts (sheep, goats, cattle, pigs) while grazing. The eggs develop into larvae that pass through the intestinal mucosa into the blood and on to the liver and other organs (e.g., lungs, heart, spleen), where they grow into vesicular formations called fins or cysts. Within these cysts, thousands of "heads" are formed, each of which can develop into new tapeworms as soon as tissue containing cysts is eaten by a dog. In humans, who represent a false intermediate host for this parasite, the clinical picture is called cystic echinococcosis. Humans become infected via dirt and smear infection by ingesting E. granulosus eggs from dog feces.
Dogs are generally considered free of worm infestation with E. granulosus in Austria. The fox tapeworm is detectable on average in every third to fourth fox in Northern Tyrol, and almost in every second fox in Vorarlberg.
In Austria, organs and muscle of all slaughtered animals, which may also be possible intermediate hosts of echinococci, are examined for the presence of worm fins and cysts. If such parasite stages are detected, no species differentiation of parasites is provided. Carcasses are declared weak-finned or strong-finned. Strong-finned carcasses are classified as unfit for human consumption and discarded. Weakly finned carcasses may be rendered usable by freezing under the control of the official veterinarian.
Last updated: 07.08.2023