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echinococcosis

Monday 5 December 2005

Definition: Echinococcosis, which is often referred to as hydatid disease or echinococcal disease, is a parasitic disease that affects both humans and other mammals, such as sheep, dogs, rodents and horses.

There are three different forms of echinococcosis found in humans, each of which is caused by the larval stages of different species of the tapeworm of genus Echinococcus:
- cystic echinococcosis (also known as unilocular echinococcosis), which is caused by Echinococcus granulosus
- alveolar echinococcosis (also known as alveolar colloid of the liver, alveolar hydatid disease, alveolococcosis, multilocular echinococcosis, “small fox tapeworm”), which is caused by Echinococcus multilocularis
- polycystic echinococcosis (also known as human polycystic hydatid disease, neotropical echinococcosis), which is caused by Echinococcus vogeli and very rarely, Echinococcus oligarthus.

Alveolar and polycystic echinococcosis are rarely diagnosed in humans and are not as widespread as cystic echinococcosis, but polycystic echinococcosis is relatively new on the medical scene and is often left out of conversations dealing with echinococcosis, and alveolar echinococcosis is a serious disease that not only has a significantly high fatality rate but also has the potential to become an emerging disease in many countries.

Types

- cystic echinococcosis (Echinococcus granulosus)
- alveolar echinococcosis (Echinococcus multilocularis)
- polycystic echinococcosis (Echinococcus oligarthus)

Hydatid disease is caused by hydatid cysts

Hydatid disease is caused by the larval forms of Echinococcus tapeworms. E. granulosus is the most frequent parasite, whereas E. multilocularis causes a more aggressive clinical disease.

  • Echinococcus granulosus :
    • classic form of hydatid cyst
    • affects liver, lung, kidneys, spleen, brain, musculoskeletal system, heart
  • Echinococcus multilocularis :
    • alveolar (multilocular) hydatidosis

Structural components of the hydatid cyst

- outer acellular laminated membrane
- germinal membrane
- protoscolices, attached and budding from the membrane

Localization

- pulmonary echinococcosis (pulmonary hydatid cyst)
- hepatic echinococcosis (hepatic hydatid cyst)
- cardiac echinococcosis (cardiac hydatid cyst)