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