Echinococcus granulosus (细粒棘球绦虫)

GENERAL INTRODUCTION Worldwide distribution Extra-intestinal tapeworm Small tapeworm Laval infection of E. granulosus may cause serious clinical disease ---hydatidosis/ hydatid disease

Morphology Only 2-8 mm long Usually comprises of- Scolex: with four suckers and 2 circular rows of hooks neck immature proglottid mature proglottid gravid proglottid The eggs of E. granulosus and Teania spp. are indistinguishable

Hydatid Cyst: Round & cystic Wall – cuticle layer, germinal layer Contents cystic fluid, brood capsules, protoscolex, daughter & grand daughter cysts (hydatid sands)

Hydatid cyst Brood capsule Cuticle layer Germinal layer Daughter cyst Granddaugher cyst Protoscolex Brood capsule Brood capsule

Hydatid cyst

Daughter cysts

protoscolex

Life cycle

Definitive host: dog & other canine Intermediate host: sheep, cattle, camel & human Infective stage: egg (gravid proglottid) Sites of hydatid: liver, lungs, abdominal cavity, spleen, kidneys, heart, bones, central nervous system etc Man is a dead end host

Adult worms in intestine of dog

Pathogenesis Cause Hydatid Disease (Hydatidosis) Sites of hydatid cyst: liver, lungs, abdominal cavity, spleen, kidney, heart, bones, brain etc Analysis of 15,289 cases in Xinjiang,China Liver 69.97% Lung 19.3% Abdominal cavity 3%

Clinical menifestations Depends on the size, the location and the number of cyst. Pressure –by tremendous size of the cyst. results in disfunction of liver, lung or nervous system Allergy -due to rupture of cyst, may cause severe allergic reaction Regeneration – due to rupture of cyst, intracystic protoscolex or germinal layer may be transplanted and result in multiple secondary infection Secondary regeneration 5.3% Toxicosis by secretion of worm

Surgical removal of the cysts

Diagnosis History of contacting with sheep & dogs Clinical symptoms of a slow-growing tumor accompanied by eosinophilia are suggestive Parasitological examination for finding scolexes, brood capsules & daughter cysts Cysts in organs or calcified cysts can be visualized using x-rays, CT & B-ultrasound examination Biopsy are forbidden unless during operation

Serological examination for specific Ab or Cag. Intradermal (Casoni) test with hydatid fluid is useful. Antibodies against hydatid fluid antigens have been detected in a sizable population of infected individuals by ELISA or indirect hemagglutination test.

CT, brain B-ultrasound, liver CT, liver X-ray, lung

Man's arm showing positive skin test for hydatid disease

Epidemiology World distribution. South America (Argentina, Brazil, Uruguay etc ),North America (American, Canada etc) Europe(Iceland, Russia, France, Spain etc), Africa (Kenya, Libya, Egypt, Tunisia etc ).

Endemic Factors Contamination of the feces by infected dogs Intimate contact between dog, herbivorous animal and man in local district Traveling to endemic areas & importing from endemic areas

Control and treatment Regular treatment of infected dogs to reduce worm load. Prevention of dogs from eating infected offals of domestic animals(sheep,etc) in the endemic areas. Health education and strict personal hygiene. Avoidance of unnecessary contact with infected dogs. Surgery is still remains the mainstay of the treatment of hydatid disease. Albendazole have proved to be effective against hydatid cyst(for median or small size cysts).

Summary T. solium T. saginata E. granulosus Proglottides 700-1000 1000-2000 only 3 Rostellum present absent present Hooks 25-50 absent 24-48 Uterine branches 7-13 15-30 unregularly branched Definitive host human human dog/wolf Intermediate host pig/human cattle sheep/human Infective stage egg/cysticercus cysticercus egg