Page 129 - Medical Parasitology_ A Textbook ( PDFDrive )

122 11 Cestodes: Tapeworms

Procercoid larvae develop in body cavity of crustaceans. (5) Infected crustaceans
are ingested by second intermediate host (e.g. fish, reptiles, amphibians) and procer-
coid larvae develop into plerocercoid larvae. (6) Predator (dogs and cats) eats
infected second intermediate host. (7) The plerocercoid larvae develop into adults in
the small intestine of dogs and cats. (8) Human acquires infection by ingesting pro-
cercoid larvae in crustaceans or by ingesting plerocercoid larvae in second interme-
diate hosts or by applying raw poultices of the second intermediate hosts containing
plerocercoid larvae on open wounds, lesions or the eyes for medicinal reasons.

Pathogenesis and Clinical Features
The sparganum (plerocercoid larva) are liberated from the second intermediate host
(fish, reptiles, amphibians) in the human intestine. Humans can also acquire infection
by ingesting cyclops containing procercoid larvae in contaminated water. The pro-
cercoid larvae will develop to the plerocercoid larvae and they will penetrate the
intestinal wall and migrate to subcutaneous tissue and other organs. The early migra-
tory stages are asymptomatic. When it reaches its final site, it begins to grow, causing
painful inflammatory reaction in the surrounding tissues. The larvae do not encyst.
Clinical features of sparganosis depend on the organs or tissues affected which
include subcutaneous nodules, periorbital oedema and in the CNS may cause sei-
zures, parasthesias and hemiparesis.

Diagnosis
1. Surgical removal of the nodules and demonstration of the plerocercoid larva.
2. Antisparganum ELISA test.
3. CT and MRI scans are useful for diagnosis of cerebral sparganosis.

Treatment
Surgical removal is the treatment of choice. Antihelminthic drugs are not effective
to treat infection with these larvae.

Prevention and Control
1. Filter and boil drinking water to remove and kill cyclops
2. Eating properly cooked fish or meat of reptiles and amphibians
3. Avoid applying raw meat of frogs and snakes as poultices on wounds

Cyclophyllidean Tapeworms

Taenia saginata and Taenia solium

Common name
Taenia saginata Beef tapeworm
Taenia solium Pork tapeworm

Distribution
Taenia saginata and Taenia solium have a worldwide distribution.