Hydatid tapeworm, dog tapeworm (Echinococcus granulosus) – one of the species of tapeworm parasitizing in the small intestine. It is small and does not exceed 6 mm in length. It has 3-4 segments and has a has a rostellum with hooks and suction cups. The tapeworm development cycle is complicated as it requires two hosts: intermediate and definitive. The intermediate host may be: humans, sheep, cattle, pigs, horses, wild boars, dogs, roe deer, deer, hares, rabbits. The definitive host are: dogs, wolves, foxes and cats. The source of a dog tapeworm infection may be contact with faeces of a dog or a fox, contaminated water and forest vegetation. Eggs also often stick to animal hair, which facilitates their spreading. The main habitat of dog tapeworm larvae in the body is the liver, the spleen and the lungs. Symptoms of echinococcosis depend on the location of the cyst. This may lead to hepatic failure, biliary tract inflammation and mechanical jaundice. A tapeworm located in the lungs can cause dyspnea, a cough; if located in the brain, it can cause visual and consciousness disturbances.