Echinococcosis

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Overview

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.

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.


Symptoms

Pain in the upper right part of the abdomen (liver cyst)

Increase in size of the abdomen due to swelling (liver cyst)

Bloody sputum (lung cyst)

Chest pain (lung cyst)

Cough (lung cyst)

Severe allergic reaction (anaphylaxis) when cysts break open.

Causes

If a parasitic tapeworm infects you, echinococcus will develop. The parasite enters a host, which is usually an animal, such as a dog, sheep, or goat. The worm lives in the bowels of the animal and releases its eggs into the animal’s feces.


You’re most likely to contract the infection when you eat food that has been contaminated with animal feces. After eating contaminated food, the incubation period is usually a few months long.


This means it takes a few months before symptoms appear. Certain strains of the parasite can have a longer incubation period that may last up to a few years.

Risk factors

The most common mode of transmission to humans is by the accidental consumption of soil, water, or food that has been contaminated by the fecal matter of an infected dog. Echinococcus eggs that have been deposited in soil can stay viable for up to a year.

One risk factor for contracting the parasite is exposure to the feces of dogs, cattle, pigs, or sheep. For example, if you work on a farm with these animals, you may be at higher risk.


Cases of the infection have been reported in the United States, but the risk is higher in countries where the parasite is more common.


Another risk factor is taking in food or water contaminated with the tapeworm eggs.

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Complications

Complications of hepatic hydatid disease: rupture of hepatic hydatid cysts. Rupture of hepatic hydatid cysts occurs in about 35% of cases, with communicating rupture being the most common type (15%), followed by contained rupture (12%) and direct rupture (6%) [7].

Prevention

echinococcosis is controlled by preventing transmission of the parasite. Prevention measures include limiting the areas where dogs are allowed and preventing animals from consuming meat infected with cysts.


Prevent dogs from feeding on the carcasses of infected sheep.

Control stray dog populations.

Restrict home slaughter of sheep and other livestock.

Do not consume any food or water that may have been contaminated by fecal matter from dogs.

Wash your hands with soap and warm water after handling dogs, and before handling food.

Teach children the importance of washing hands to prevent infection.

Alveolar echinococcosis can be prevented by avoiding contact with wild animals such as foxes, coyotes, and dogs and their fecal matter and by limiting the interactions between dogs and rodent populations.


Do not allow dogs to feed on rodents and other wild animals.

Avoid contact with wild animals such as foxes, coyotes and stray dogs.

Do not encourage wild animals to come close to your home or keep them as pets.

Wash your hands with soap and warm water after handling dogs or cats, and before handling food.

Teach children the importance of washing hands to prevent infection.