Echinococcosis


Echinococcosis

Description, Causes and Risk Factors:

Echinococcosis is a parasitic disease caused by infection with tiny tapeworms of the genus Echinocococcus. Echinococcosis is classified as either cystic echinococcosis or alveolar echinococcosis.

Echinococcosis

The incubation period for echinococcosis varies from months to years. It can be as long as 20-30 years, if the cyst grows slowly and is not in a critical location.

Echinococcosis is caused by several species of Echinococcus, tiny cestode parasites in the family Taeniidae. Currently recognized species include Echinococcus granulosus sensu lato, E. multilocularis, E. vogeli, E. oligarthrus and possibly E. shiquicus.

    Cystic echinocccosis (CE), also known as hydatid disease, is caused by infection with the larval stage of Echinococcus granulosus, a ~2-7 millimeter long tapeworm found in dogs (definitive host) and sheep, cattle, goats, and pigs (intermediate hosts). Although most infections in humans are asymptomatic, CE causes harmful, slowly enlarging cysts in the liver, lungs, and other organs that often grow unnoticed and neglected for years.

  • Alveolar echinococcosis (AE) disease is caused by infection with the larval stage of Echinococcus multilocularis, a ~1-4 millimeter long tapeworm found in foxes, coyotes, and dogs (definitive hosts). Small rodents are intermediate hosts for E. multilocularis. Although cases of AE in animals in endemic areas are relatively common, human cases are rare. AE poses a much greater health threat to people than CE, causing parasitic tumors that can form in the liver, lungs, brain, and other organs. If left untreated, AE can be fatal.

Echinococcosis is not transmitted from person to person. Humans can transmit the infection to the definitive hosts if affected tissues are eaten, but this does not occur in most societies due to cultural practices.

Humans act as intermediate hosts for Echinococcus spp., and are infected when they ingest tapeworm eggs from the definitive host. The eggs may be eaten in foods such as vegetables, fruits or herbs, or drunk in contaminated water. They can also stick to the hands when a person pets an infected dog or cat, handles a wild animal or its carcass, or touches contaminated soil and vegetation. Uninfected pets may carry the eggs on their fur if they contact the feces of infected wild hosts. This is probably more common in dogs, which may roll in feces.

Symptoms:

Echinococcosis may not produce any symptoms for 10 or 20 years because the cysts grow slowly. When the symptoms appear, they can include:

    Abdominal pain.

  • Chest pain.

  • Cough that won't go away.

  • Unintended weight loss.

  • Weakness.

  • Jaundice (yellowing of the skin and the whites of the eyes).

  • Fever.

  • Bloody stools.

  • Headache.

  • Seizures.

Diagnosis:

In humans, echinococcosis is diagnosed mainly with imaging techniques such as ultrasonography, radiology, magnetic resonance imaging (MRI) or CT scanning, supported by serology. Serological tests used in humans include enzyme-linked immunosorbent assays (ELISAs), indirect immunofluorescence, indirect hemagglutination, immunoblotting and latex agglutination. Complement fixation is now rarely used. Some people with cysts do not develop detectable antibodies. False positives, which include cross-reactions with other taeniid cestodes, are also possible.

Treatment:

Cysts are often removed surgically. The success rate varies with the species of Echinococcus and the location and size of the cysts. In some situations, particularly with E. multilocularis or E. vogeli infections, it may not be possible to remove the entire cyst. Long-term post-surgical treatment with antiparasitic drugs such as albendazole or mebendazole may shrink or destroy the organism, help prevent it from re-growing and/or ameliorate the symptoms. Drug treatment is also an alternative to surgery in some cases. Another treatment option is the removal of most of the cyst contents and the introduction of an anthelminthic chemical into the cyst under ultrasonographic guidance (PAIR - puncture, aspiration, injection, and re-aspiration). Sometimes (e.g. small inactive cysts in certain locations) a “wait and see” approach might also be appropriate. In severe cases of alveolar echinococcosis, a liver transplant may be an option.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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