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Diseases » Tapeworms » Causes

Causes of Tapeworms

Contents

Tapeworms Causes: Book Excerpts

Related information on causes of Tapeworms:

As with all medical conditions, there may be many causal factors. Further relevant information on causes of Tapeworms may be found in:

Causes of Tapeworms: Online Medical Books

16 MEDICAL BOOKS ONLINE! Review excerpts from medical books online, free, without registration, for more information about the causes of Tapeworms.

Hookworm disease: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

Both forms of hookworm disease are transmitted to humans through direct skin penetration (usually in the foot) by hookworm larvae in soil contaminated with feces containing hookworm ova. These ova develop into infectious larvae in 1 to 3 days. Larvae travel through the lymphatics to the pulmonary capillaries, where they penetrate alveoli and move up the bronchial tree to the trachea and epiglottis, where they're swallowed and enter the GI tract. When they reach the small intestine, they mature, attach to the jejunal mucosa, and suck blood, oxygen, and glucose from the intestinal wall. These mature worms then deposit ova, which are excreted in the stool, starting the cycle anew. Hookworm larvae mature in approximately 5 to 6 weeks.

Hookworm disease, affecting billions of people worldwide, is most common in moist tropical and subtropical regions. There's little risk of aquiring hookworm disease in the United States because of advances in sanitization and waste control.

» READ BOOK EXCERPT ONLINE »

Source: Professional Guide to Diseases (Eighth Edition), 2005

Tapeworm: Tapeworm - pathophysiology
(The 5-Minute Pediatric Consult)

Beef tapeworm:
- Cattle (intermediate host) ingest the eggs of T. saginata in contaminated feeds. The eggs hatch, releasing embryos. The embryos penetrate the intestinal mucosa, enter the bloodstream, and settle in various tissues, where they develop into larvae. Larvae in undercooked meat are consumed by humans and mature into adult tapeworms within the human (definitive host) GI tract. They grow up to 25 m in length.
Pork tapeworm: Humans are the only definitive host for the adult pork tapeworm, whereas both humans and pigs are intermediate hosts for its embryonic form, cysticercus.
- Pigs (intermediate host) ingest T. solium eggs. In the intestine, the eggs release embryos that penetrate the mucosa, enter the bloodstream, and settle in various tissues to differentiate into cysticerci (infective larvae). Cysticerci are ingested by humans (definitive host) who consume undercooked pork.
- Humans (intermediate host) ingest food contaminated with human feces containing T. solium eggs. The eggs hatch, liberating embryos (oncospheres). Penetration through the intestinal mucosa leads to blood-borne distribution to the brain, subcutaneous tissues, muscle, and eye, where they develop into cysticerci.
Fish tapeworm:
- When sewage containing D. latum eggs contaminates freshwater lakes and streams, larvae hatch into the water. These larvae are eaten by crustaceans and fish. Humans are infected when they consume these undercooked fish. The larvae mature into adult tapeworms in the intestines of humans.
Dog tapeworm:
- Larvae develop in fleas (intermediate host) after ingestion of the eggs; humans infected through accidental ingestion of infected fleas.
Echinococcosis (hydatid disease):
- Humans ingest eggs of E. granulosus through contaminated dog feces. After ingestion, the eggs hatch and release embryos (oncospheres) in the small intestine. Penetration through the mucosa leads to blood-borne distribution to the liver, lungs, and other sites, where development of cysts begins. Within the cysts, new larvae (scolices) develop, accumulate fluid, and encroach on surrounding structures.