Platyhelminths : Cestodes

• Pseudophyllidea• Diphyllobothrium latum (pernicious anemia)

• Cyclophyllidea• Taenia solium (pork tapeworm)• Taenia saginata (beef tapeworm)• Echinococcus granulosus (cystic, CE)• Echinococcus multilocularis (alveolar, AE)

A rare and emerging disease

Macroparasite example 2 : Taenia solium :

Disease Neurocysticercosis

Cestode. Unique zoonosis. Under-reported disease.

Diagnostic difficulties. Lack of epidemiological data.

Biology of Taenia solium

• Unique zoonosis : Human only known definitive host, pig intermediate host

• Humans carry both adult worms in the intestine & larval cysticercosis in the muscle & other tissues

• Infection with adult worm in humans dangerous to host & other contacts

• Under-reported disease

Symptomatology and pathology 1

• Primarily due to pressure effects of a space-occupying cyst or lesion in an organ or tissue

• CNS involvement : Neurocysticercosis (NCC) : pathology relates to number, size, type (cellulose or racemose), condition & site of cysticerci in the brain

• Active versus inactive NCC

Symptomatology and Pathology 2

• Active NCC : arachnoiditis (spinal fluid pleocytosis, increased CSF protein, positive CSF serologic test)

• Small number of patients : obstructive hydrocephalus, cranial nerve involvement, intercranial hypertension, arterial thrombosis & stroke

• Epilepsy, dementia, meningitis

Intraocular cysts : visual impairment

Location of parasites in 2188 cases of cysticercosis

• CNS 82%• Eye 17%• Subcutaneous tissue 7%

• Muscle 5%• Other organs 6%• Generalized 1%

Flisser & Craig, 2005

Diagnosis 1

Adult worms

• Stool analysis : uterine branch structure or scolex morphology after treatment

• Molecular differentiation of adult worms

• Capture ELISA for coproantigen detection

Diagnosis 2Cysticercosis

• Imaging methods (CT scan useful for brain & calcified cysts ; MRI not but excellent for detecting active cysts in soft tissue)

• Serology (ELISA versus Immunoblot)

Epidemiology :

cysticercosis

• Retrospective case finding• fixed time period, annual incidence rate per 100,000 population

• Active screening• Mass radiological imaging surveys

• Immunodiagnostic surveys

• Autopsy surveys

Cysticercosis in communities

• Endemic focus: Rural Latin America• Major risk factor: current or past case of intestinal Taenia in the household

• Non-endemic community: New York City• Significant number of human cysticercosis cases in an Orthodox Jewish community

Treatment : cysticercosis

• Until recently symptomatic patients : anticonvulsants, corticosteroids, surgery

• Chemotherapy • CT useful for monitoring• Active parenchymal brain cysts and subarachnoid (racemose) cysts : albendazole

• Albendazole also effective against ocular cysticercosis

• Alternative drug : praziquantel less effective

Control : Taenia solium

• Freezing and appropriate cooking of pork

• Identification and treatment of Taenia carriers (mass treatment ?)

• Improved health education, prevention of vegetables irrigated with contaminated water

• Confinement of pigs• Porcine vaccine