Hydatid cyst disease, caused by infection with the neonatal stage of the cestode of the family Echinococcus granulosus, has a global distribution that is of great health and economic importance.
Iran is also considered one of the hyperendemic areas of this disease. This disease causes significant health and economic losses in humans and domestic animals. Hydatidosis is a common infection between humans and animals.
The definitive host of this parasite is dogs and canids, and its intermediate hosts are livestock such as sheep, cattle, and goats. Humans are also infected in an incidental form. The larval forms of the parasite appear in the intermediate hosts as large cysts in the internal organs, especially the liver and lungs.
Geographical distribution:
Geographical distribution exists throughout the world, but it is of particular importance in areas where sheep are raised traditionally and using herding dogs.
Evolution:
The transmission of this disease is domestic, with dogs as the main host and livestock as the intermediate host. The adult worm is replaced in the small intestine of dogs and other carnivores.
The fertile bands disintegrate in the small intestine of dogs and the eggs are excreted with feces. If the eggs are placed on forage, they are eaten by various animals while grazing, and the six-hooked embryo is released in the duodenum and penetrates the intestinal wall and reaches various tissues through the bloodstream.
Carnivores become infected by eating hydatid cysts in the intestines of the intermediate host. Humans become infected by petting an infected dog and by putting contaminated hands in their mouths. They also become infected through vegetables contaminated with dog feces.
The eggs enter through the mouth and under the influence of digestive juices, the six-hooked embryo comes out of the egg shell and after piercing the intestinal wall, reaches the liver through the venous bloodstream. Most of the embryos are replaced in the liver. Some of them enter organs such as the spleen, lungs, brain, etc. and become cysts.
Clinical symptoms:
Human infection occurs in most cases in childhood, and dirty hands play the most important role in transmitting the disease, and clinical symptoms appear at an older age.
Human infection with hydatid cysts does not show any specific symptoms in the early stages, but symptoms such as indigestion, loss of appetite, nausea, and sometimes vomiting may be seen. In advanced stages and with an increase and enlargement of cysts in the abdomen, symptoms such as fullness and heaviness in the abdomen and in the event of rupture of one or more cysts, symptoms of anaphylaxis can occur.
Treatment:
Today, timely diagnosis and treatment of hydatid cysts is a problem in developing countries. Treatment of hydatid cysts includes drug therapy, surgery, or a combination of both.
Drug therapy requires long-term use of antiparasitic drugs. Surgery is the main treatment and the only way to completely eliminate the cysts, but it may have side effects and risks such as death or recurrence of the cyst after surgery.
References:
Zibaei M., Sarlak A., Delfan B., Ezatpour B., Azargoon A. (2012). Scolicidal effects of Olea europaea and Satureja khuzestanica extracts on protoscolices of hydatid cysts. Korean Journal of Parasitology
Moazeni M., Nazer A. (2010). In vitro efficacy of garlic (Allium sativum) extract on scolices of hydatid cyst. World Journal of Surgery
Eslami, A. (2009): Veterinary Helmintology, Cestodes, Volume 2, Tehran University Press
