What is echinococcosis?
Echinococcosis is caused by the fox tapeworm (Echinococcus multilocularis) or dog tapeworm (Echinococcus granulosus). If the tapeworm eggs enter the human body through food, for example, they can develop into so-called fins in the intestine and infect the liver and other organs. This larval stage is responsible for the development of echinococcosis in humans. An infection with the fox tapeworm is referred to as alveolar echinococcosis. An infestation with the dog tapeworm causes cystic echinococcosis. Echinococcosis varies depending on the type of tapeworm. The disease must be taken very seriously and must be treated professionally.
Echinococcosis caused by fox and dog tapeworm is a zoonosis. Zoonoses are infectious diseases that are transmitted naturally from animals to humans.
In which regions is fox tapeworm found?
The distribution of the fox tapeworm (Echinococcus multilocularis) is mainly restricted to the northern hemisphere. In Europe, it is mainly found in northern Switzerland (Mittelland, Jura), eastern France, western Austria and southern Germany (Bavaria, Baden-Württemberg). Outside Europe, it occurs in northern China, Siberia and northern Japan.
In which regions is the dog tapeworm found?
The dog tapeworm (Echinococcus granulosus) is found worldwide. In Europe, it is most common in the Mediterranean countries and the Balkans. Dog tapeworms are also found in the Middle East, North and East Africa, Central and South America and Australia.
Echinococcosis: causes and risk factors
The cause of echinococcosis is a parasite infestation with the fox tapeworm or dog tapeworm. In both cases, the larvae of the tapeworms – the so-called Finns – are responsible for the disease. The disease varies depending on the type of parasite:
- Dog tapeworms cause cystic echinococcosis in humans.
- Fox tapeworms cause alveolar echinococcosis.
Causes of cystic echinococcosis
Cystic echinococcosis is caused by an infection with the dog tapeworm (Echinococcus granulosus). The fins of the dog tapeworm prefer to settle in the liver. However, they can also affect the lungs and, in rare cases, the brain. A large cyst (bladder) forms in the target organ, which is filled with fluid. An infection with the dog tapeworm becomes noticeable as soon as the cyst is so large that it displaces healthy tissue. Cysts can reach a diameter of 20 centimeters and more.
Causes of alveolar echinococcosis
The cause of alveolar echinococcosis is an infection with the fox tapeworm (Echinococcus multilocularis). It usually affects the liver. Larvae are also responsible for the infection in alveolar echinococcosis. In contrast to the dog tapeworm, however, the larvae of the fox tapeworm do not form a closed cyst, but many small vesicles (so-called alveoli) that penetrate the tissue of the target organ. These reach a diameter of a few millimeters up to two centimeters. This makes it more difficult to remove the pathogen surgically. The fox tapeworm larvae proliferate in the liver tissue and increasingly break it down.
How are tapeworms transmitted?
During their development from egg to larva to adult tapeworm, tapeworms change their host several times (so-called host change). Infected humans serve as intermediate hosts for the tapeworms. The intermediate hosts are usually small rodents in the case of fox tapeworm or sheep in the case of dog tapeworm. Affected people are so-called false hosts. The final hosts are foxes or dogs, rarely cats. The final hosts excrete the tapeworm eggs in their feces. An infestation in humans is very rare and life-threatening. It is initially painless and symptom-free. The pathogens mainly affect the liver or lungs. The larvae of the tapeworm develop there. They grow very slowly and destroy the organ. More than ten years can pass between infection and the first symptoms.
There are various possible sources of infection for human infestation by the fox tapeworm or dog tapeworm.
Overview: Possible transmission routes for tapeworms
- Eating unwashed food that grows close to the ground, for example berries, wild berries, mushrooms, vegetables, lettuce and fallen fruit
- Direct contact with dogs, wolves, foxes or cats
- Contact with contaminated soil
Risk factors for echinococcosis
The risk of infection with the fox or dog tapeworm increases the more widespread tapeworms are in an area. Close contact with possible final hosts (such as dogs and cats) and a lack of hygiene also increase the risk of contracting the disease. The worm eggs are not only contained in the animals’ feces, but can also adhere to their fur. There is also an increased risk of infection if you do not regularly give your dog or cat a worming treatment. Transmission of tapeworm eggs from person to person is not possible.
Symptoms: Echinococcosis often remains undetected for a long time
People who are infected with dog or fox tapeworm often do not experience any symptoms for a long time. It usually takes many years before the first symptoms appear. The symptoms vary depending on which tapeworm a person is infected with.
Symptoms of fox tapeworm
Infestation with the fox tapeworm (Echinococcus multilocularis) progressively destroys the liver. The infection usually runs its course for years without symptoms. The most common symptom of advanced alveolar echinococcosis is non-specific upper abdominal discomfort. By the time we detect the fox tapeworm infection, the destruction of the liver is often already well advanced.
Symptoms of dog tapeworm
In the case of an infection with the dog tapeworm (Echinococcus granulosus), the first symptoms usually appear when the cyst (hydatid) formed by the larvae is so large that it displaces healthy tissue. Depending on which organ is affected and how large the cyst is, the symptoms vary. In 70 percent of cases of dog tapeworm, the larvae settle in the liver. However, the larvae can also infect other organs such as the lungs (20 percent) or, more rarely, the brain. Possible symptoms of cystic echinococcosis:
- Liver infection: feeling of pressure in the upper abdomen, upper abdominal pain, jaundice and tiredness
- Lung infestation: breathing difficulties and coughing
Echinococcosis: diagnosis at the USZ
If an infection with the fox tapeworm or dog tapeworm does not cause any symptoms, echinococcosis often remains undetected for a long time. The discovery of a worm disease is usually an accidental finding.
If a fox or dog tapeworm infection is suspected, we have several imaging techniques at our disposal for diagnosis. We can detect tapeworms in the body using ultrasound (sonography), computer tomography (CT) or magnetic resonance imaging (MRI), for example, and visualize the inflammation of the liver parenchyma caused by them using positron emission tomography(PET/CT or PET/MR).
For a reliable diagnosis, the blood is also tested for certain antibodies. However, if no antibodies are detectable, this is not proof that there is no infection with the fox or dog tapeworm.
Echinococcosis consultation
In this special consultation, we work very closely with various clinics and institutes of the University Hospital Zurich and the University of Zurich in order to offer our patients the best possible therapies and treatments.
Echinococcosis: prevention, early detection, prognosis
You can prevent fox and dog tapeworm infestation by following these tips:
- Do not eat unwashed plants such as wild berries, wild mushrooms, lettuce, vegetables or fallen fruit.
- Ensure hygienic handling of potential final hosts (dogs, cats).
- Wash your hands after direct contact with potential final hosts.
- Deworm your pets (dog, cat) regularly.
Tip: You can prevent infection with fox or dog tapeworm by briefly boiling food intended for consumption. This kills the fox tapeworm and dog tapeworm eggs. Deep-freezing food does not help.
Is there a vaccination against echinococcosis?
There is no vaccination against echinococcosis caused by the fox and dog tapeworm.
Course and prognosis
The course of echinococcosis depends on several factors:
- Which organ is affected?
- How many cysts have formed and how big are they?
- How old are those affected?
- Is it possible to remove the parasites surgically?
Prognosis for fox tapeworm
Fox tapeworm infestation is considered more dangerous than dog tapeworm infestation. If an infestation with fox tapeworm is not treated, the infection is fatal.
Prognosis dog tapeworm
The large cysts (blisters) that form in a dog tapeworm infestation are generally easier to remove than the many small blisters (alveoli) in a fox tapeworm infestation.
Treatment depends on the stage of the disease
The treatment for an infestation with fox or dog tapeworm depends on the stage of echinococcosis. Treatment takes place in specialized hospitals.
If possible, fox and dog tapeworms are surgically removed. Medication is also available against the fox or dog tapeworm. Active substances such as albendazole or mebendazole are suitable for treatment. These agents inhibit or prevent further growth of the parasites.
