Chapter 3Infectious Diseases Related To Travel

Jeffrey L. Jones

INFECTIOUS AGENT

Taeniasis is caused by intestinal infection with the adult stage of tapeworms Taenia solium (pork tapeworm) and T. saginata (beef tapeworm).

MODE OF TRANSMISSION

Humans acquire T. solium when they eat raw or undercooked contaminated pork; the adult worm then develops in the intestine. Eggs passed by humans in the stool are infectious to pigs; the larval stage lives in the flesh of pigs (pig cysticercosis). Eggs passed by humans in the stool are also infectious to humans and can be transferred by the fecal-oral route. Eggs are infectious when shed. When humans ingest T. solium eggs, the larvae penetrate the intestinal wall and spread to the tissues via the blood and lymphatics (human cysticercosis, see the Cysticercosis section earlier in this chapter).

T. saginata eggs passed in the stool of an infected person are infectious only to cattle; the larval stage lives in the flesh of cattle (cysticercosis bovis) and infects humans when they eat raw or undercooked contaminated beef. T. asiatica is a third species, similar to T. saginata.

EPIDEMIOLOGY

Taeniasis is distributed worldwide but is more common where pigs and cattle can eat human feces. The highest prevalences are in Latin America, Africa, and South and Southeast Asia. The disease has been reported, but at lower rates, from Eastern Europe, Spain, and Portugal. Transmission of T. solium is rare in the United States, Canada, Western Europe, and many areas of Asia and the Pacific. The risk is higher in developing countries where inadequate sanitation leads to pork and beef contamination with larvae, as well as food and water contamination with Taenia eggs. Immigrants from endemic areas may have taeniasis or cysticercosis.

CLINICAL PRESENTATION

Taeniasis (intestinal tape worm) may be asymptomatic or associated with abdominal discomfort, weight loss, anorexia, nausea, insomnia, weakness, perianal pruritus, and nervousness. Proglottids may be passed from the rectum. Rarely, these infections result in intestinal, biliary, or pancreatic obstruction. Tapeworms can live in the intestine 30 years or longer. Eosinophilia is often present, but the duration and magnitude vary. The incubation period (time for eggs to appear in stool) is 8–10 weeks for T. solium and 10–14 weeks for T. saginata.

DIAGNOSIS

Adult tapeworm infection is identified by eggs, proglottids (segments), or tapeworm antigens in the feces or on anal swabs. Differentiation of T. solium from T. saginata is based on morphology of the scolex and gravid proglottids.

TREATMENT

Praziquantel is used to treat intestinal infections with T. solium or T. saginata. Niclosamide is an alternative but is not as widely available.

PREVENTIVE MEASURES FOR TRAVELERS

Cook meat to safe temperatures (≥150°F [65°C] throughout). Freezing (23°F [–5°C]) meat for ≥4 days will kill cysticerci. For more on the prevention of cysticercosis, see the Cysticercosis section earlier in this chapter.

BIBLIOGRAPHY

1. Abramowicz M. Drugs for Parasitic Infections. New Rochelle (NY): The Medical Letter, Inc; 2007.
2. CDC. Cysticercosis. Atlanta: CDC; 2009 [updated 2009 Jul 20; cited 2010 Oct 22]. Available from: http://www.dpd.cdc.gov/dpdx/HTML/Cysticercosis.htm.
3. CDC. Taeniasis. Atlanta: CDC; 2009 [updated 2009 Jul 20; cited 2010 Oct 22]. Available from: http://www.dpd.cdc.gov/dpdx/HTML/Taeniasis.htm.
4. Wittner M, Tanowitz HB. Taenia and other tapeworms. In: Guerrant RL, Walker DH, Weller PF, editors. Tropical Infectious Diseases: Principles, Pathogens, and Practice. 2nd ed. Philadelphia: Churchill Livingstone; 2006. p. 1327–30.