Pulmonary tapeworm cysts. Coloured chest X-ray showing hydatid cysts (opaque areas at centre right and centre left) in a patient's lungs. The cysts are caused by parasitic tapeworm larvae (Echinococcus sp.). Humans are not a natural host of the parasite, but may become infected from ingesting eggs in food that has been contaminated by the faeces of an infected animal, usually a sheep or a dog. Cysts may be formed in the lungs, brain, liver or kidneys. Pulmonary cysts can cause chest pain, wheezing and the coughing up of blood. Treatment is either with the surgical removal of the cysts, or sterilising and draining them.