The eggs hatch in the duodenum and larvae migrate through the gut wall. Blood stream dissemination follows usually to the liver, but any tissue or org

widespread in dogs and livestock (sheep, goats, cattle and camels) and in man (b) Alveolar E multilocularis, the ^malignant1 hydatid is transmitted between foxes and rodents, but is very rare in humans LIFE CYCLE OF ECHINOCOCCUS - The adult worm lives in the small intestine of the dog. Eggs are shed in the faeces and ingested by sheep, usually from contaminated pasture. The eggs hatch in the duodenum and larvae migrate through the gut wall. Blood stream dissemination follows usually to the liver, but any tissue or organ can become infected. The larva develops into a hydatid cyst containing many scolices/ When infected organs of the sheep are ingested by the dog, the scolices attach themselves to the small bowel mucosa and develop into adult worms/ Man becomes infected after ingestion of eggs after contact with dogs faeces or via contaminated food stuffs. Clinical features - Hydatid cysts especially if calcified may be asymptomatic and first noted incidentally during routine physical examination. Symptoms and signs depend on the organ affected. 1. LIVER - Hydatid cyst may present as - (a) Painless hepatomegaly. (b) Pyrexia of unknown origin following secondary pyogenic infection. (c) Jaundice due to pressure on the bile ducts. (d) Severe systemic reaction following rupture into peritoneal cavity, gut itself or pleural cavity. (e) Cholangitis from rupture into biliary tree. 2. LUNG - Pulmonary hydatid cyst can present as - (a) Solitary or at times multiple cysts, on plain radiograph. (b) Shortness of breath or chest pain if cyst is large. (c) Haemoptysis following ulceration into a bronchus. (d) Expectoration of watery fluid and daughter cysts fgrape skin' expectoration) following rupture into the bronchial tree. Respiratory distress may follow due to aspiration of fluid elsewhere in the lungs, and may be associated with urticaria and anaphylactic shock. (e) Fever, cough and purulent sputum, if secondary pyogenic infection occurs. 3. OTHER ORGANS - Presence of cysts in - (a) Brain -Epilepsy or hemiplegia. (b) Long bones - Pathological fractures. (c) Spleen - Splenomegaly. (d) Kidneys - Hematuria. (e) Spinal cord - Seizures or signs of increased intracranial pressure of subacute onset and progressive course. Root pains- and motor or sensory deficits. (f) Thyroid - Goitre. (g) Behind the eye - Exophthalmos. (h) Abdomen - Pseudocycesis from rapidly growing cysts. Diagnosis - 1. DEMONSTRATION OF HYDATID CYSTS - (a) Chest radiograph - various signs are - (a) Classical appearance of a circular shadow sharply defined with no reaction in surrounding lung parenchyma. The cyst may change shape on maximum inspiration an expiration (Escudero nimerove sign). (b) Crescent sign or pulmonary meniscus sign - If the cyst communicates with a bronchus, a cap of air may be seen above the cyst (also seen in lung abscess partially filled with ins pisated pus or blood clot, tuberculous cavity containing a Rasmussen aneurysm, and in intracavitary fungal ball). (c) Double arch (Gumbo's) sign - As more sir enters between pericyst and endocyst, the shrinking cyst ruptures with resultant air fluid level within the endocyst capped with crescent of air between pericyst and endocyst. (d) Water lilly sign - With further separation of endocyst and evacuation of fluid, a wavy endocyst membrane floats on top of remaining TREATMENT - Praziquantel in three equal doses of 20 mg/kg at 4h intervals with meals. Apart from mild side-effects of drowsiness, headache, dizziness, etc. , a syndrome of severe abdominal pain followed by bloody diarrhoea may occur. PREVENTION - 1. Protection of snail habitats from infection by provision of clean water and toilet facilities, and health education. 2. Mass therapy with oxamniquine, metriphonate or praziquantel to reduce amount of egg excretion. 3. Snail destruction by improved irrigation methods and use of molluscicides. 4. Prevention of infection by wearing protective clothing. 18. HYDATID DISEASE : Definition - Hydatid disease of man is zoonosis caused by infection with tapeworm larvae of the genus Echinococcus. There are two forms - (a) Cystic: The much more common E. granulasus causes unilocular hydatid cysts and is widespread in dogs and livestock (sheep, goats, cattle and camels) and in man (b) Alveolar E. multilocularis, the `malignant' hydatid is transmitted between foxes and rodents, but is very rare in humans. LIFE CYCLE OF ECHINOCOCCUS - The adult worm lives in the small intestine of the dog. Eggs are shed in the faeces and ingested by sheep, usually from contaminated pasture. The eggs hatch in the duodenum and larvae migrate through the gut wall. Blood stream dissemination follows usually to the liver, but any tissue or organ can become infected The larva develops into a hydatid cyst containing many scolices. When infected organs of the sheep are ingested by the dog, the scolices attach themselves to the small bowel mucosa and develop into adult worms. Man becomes infected after ingestion of eggs after contact with dogs faeces or via contaminated food stuffs. Clinical features - Hydatid cysts especially if calcified may be asymptomatic and first noted incidentally during routine physical examination. Symptoms and signs depend on the organ affected. 1. LIVER -Hydatid cyst may present as - (a) Painless hepatomegaly. (b) Pyrexia of unknown origin following secondary pyogenic infection.