Echinococcosis is a parasitic disease caused by a tapeworm. In developed countries it is a relatively rare condition.
Echinococcus belongs to the parasitic group of tapeworms that usually infects canine carnivores such as fox and dogs. Everyone imagines a tapeworm as several meters long worm that lives in our intestines. The intestinal existence, however, is typical for other tapeworms such as beef and pork tapeworm. Echinoccocus differs distinctively from these previous tapeworms and has quite different lifecycle.
Pork and beef tapeworms use humans as their primary host. They live in human intestines, lay eggs and these are excreted with the faeces. When the eggs get on plants, they may be eaten by animals such as pigs and cows. Pigs and cows are only secondary hosts, small tapeworm larvae infect their bodies and encapsulate in their muscle tissue forming small cysts. When a human eats poorly cooked meat of an infected animal, the larvae get into his digestive tract growing into an adult worm and the cycle repeats.
The process is similar for Echinococcus but with a one major difference – the human is just a secondary host as the primary host is a fox or a dog. Adult Echinococcus lives in the intestine of fox (or other canids), its eggs are excreted and can contaminate a plant (such as blueberries). When the eggs are eaten, they hatch into small larvae that travel through the intestinal wall into the body and affect various tissue where they ma form echinococcal cysts.
Such cyst can have even many centimeters in its diameter and it is an encapsulated unit filled with germ Echinococci.
The symptoms depend on location where the cyst develops. Frequently the growing cyst affects liver causing liver enlargement and abdominal pain located in the right upper abdominal quadrant. When liver function is disrupted, jaundice may occur. Very serious form of the disease is a cyst formed in brain tissue as it can cause potentially fatal intracranial hypertension.
If the cyst ruptures, its content may leak into the body and cause a life-threatening anaphylactic shock. It is due to a widespread allergic reaction against sudden occurrence of many foreign particles (germ tapeworms) in our body.
The cyst may be visualized by an ultrasound or other imaging methods (computed tomography, magnetic resonance imaging). Large liver cysts are palpable. The presence of a parasite may be estimated from blood test and serology allows us to confirm the presence of Echinococcus.
The cyst may be surgically removed. The operation is a bit risky as there is the risk of accidental perforation leading to the above mentioned anaphylactic shock. In addition to surgery, the physicians can use some special anti-parasitic drugs (mebendazole) that may be administered orally or directly injected into the cyst.