Echinococcosis

Echinococcosis is a rare parasitic zoonosis caused by an infection with tapeworms of the genus Echinococcus. The 2 main human forms of the disease are cystic echinococcosis, caused by Echinococcus granulosus species complex, and alveolar echinococcosis, caused by Echinococcus multilocularis. Only the latter is endemic in Belgium.

Transmission

Cystic echinococcosis
Humans become infected by ingesting food or water contaminated with egg-containing faeces from an infected dog, or by limited hand hygiene after touching an infected dog whose fur is contaminated. The dogs on their turn, have become infected by eating organs of an infected herbivorous/omnivorous intermediate host (such as sheep, goats, pig …). 

Alveolar echinococcosis
Humans become infected by ingesting food (e.g. berries, herbs …) contaminated with egg-containing fox faeces or by limited hand hygiene after touching an infected fox whose fur is contaminated. The foxes on their turn, have become infected by eating infected rodents, the intermediary host. On rarer occasions dogs, instead of foxes, are the final hosts infecting humans.

Symptoms

Cystic echinococcosis
is characterised by the development of one or more cysts, mainly in the liver (70%) or lungs (20%).

The asymptomatic period can last for years and symptoms do not appear until the cysts are large enough to cause symptoms.

Symptoms depend on the location of the cyst, but commonly include upper abdominal discomfort, lack of appetite and weight loss.

Alveolar echinococcosis
has a more malignant course than cystic echinococcosis, although it can take 5-15 years before symptoms develop.

The infection starts in the liver in 90% of cases, but also affects other organs and blood vessels.

Symptoms may resemble those of liver cancer and cirrhosis of the liver.

Diagnosis

Medical imaging (Ultrasound, MRI, CT scan), serology (ELISA combined with Western blot), histology and molecular biology (PCR on tissue) are often used in combination to diagnose echinococcosis.

Treatment

Cystic echinococcosis
Surgical removal of the cysts is the first-line treatment. Other options include treatment with benzimidazoles and a less invasive procedure (“PAIR”) in which the cysts are punctured, aspirated, reinjected with a protoscolecide agent and reaspirated.

Alveolar echinococcosis
Early diagnosis and radical surgical removal of the affected tissue followed by treatment with benzimidazoles (albendazole) are essential. If not all affected tissue can be surgically removed, long-term treatment with benzimidazoles and intensive follow-up of the patient is necessary. In some cases, a liver transplantation is necessary.

Geographical spread

Cystic echinococcosis
E. granulosus sensu lato occurs all over the world, especially in rural areas where dogs can eat organs of infected animals like sheep. In Europe, E. granulosus is endemic in Southern Europe and around the Balkans (especially Romania).

It has not yet been detected in Belgium, so all cases of cystic echinococcosis have been infected abroad.

Alveolar echinococcosis
Echinococcus multilocularis is found worldwide, especially in the northern latitudes of Europe, North America and mostly Asia, with 90% of the cases occurring in China.

In Belgium more than 50% of red foxes are infected in Wallonia, but only 2% in Flanders. This could be explained by the absence of intermediary hosts in the Northern part of the country. 

Prevention

Cystic echinococcosis
which is not transmitted in Belgium, can be prevented by taking the following measures in endemic areas:

  • Prevent dogs from feeding on the carcasses of infected sheep (slaughterhouse hygiene).
  • Regularly deworm dogs.
  • Control stray dog populations.
  • Do not consume any food or water that may have been contaminated by dog faeces.
  • Perform proper hand hygiene.

Alveolar echinococcosis
which can be contracted in Belgium (especially in Wallonia), can be prevented by taking the following measures:

  • Do not eat food that could be contaminated with fox faeces (close to the ground).
  • Do not touch dead foxes. 
  • Use gloves when gardening.
  • Put a high fence (1 meter) around the vegetable garden.
  • Avoid composting if foxes are seen in the vicinity of the garden.
  • Perform proper hand hygiene.
  • Do not allow dogs to feed on rodents.
  • Regularly deworm dogs.

Sciensano, in collaboration with the National Reference Laboratory at CHU de Liège, is responsible for the surveillance of echinococcosis by collecting information on cases occurring in Belgium.

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