Taeniasis

Victorian statutory requirement

Notification and school exclusion are not required.

Infectious agent

Taenia solium (pork tapeworm) causes both intestinal infection with the adult tapeworm and somatic infections with the larvae (cysticerci).

Taenia saginata (beef tapeworm) causes only intestinal infection with the adult tapeworm in humans.

Identification

Clinical features
Taenia saginata infections are often asymptomatic apart from the anal passage of tapeworm segments. Infection may be associated with epigastric pain, diarrhoea and weight loss.

Taenia solium adult worm infections are also usually asymptomatic. Many tissues and organs may be infected by the larval form (cysticercosis). Neurocysticercosis is a serious but rarely fatal complication which may be manifest as headaches, epileptiform seizures and visual or psychiatric disturbances.

Method of diagnosis
Infection with an adult tapeworm can be diagnosed through the identification of segments, eggs or the head of the parasite in faeces or perianal swabs. Microscopic examination of the eggs cannot differentiate between the two species.

Specific serological tests are available to support the clinical diagnosis of taeniasis.

Subcutaneous cysticerci may be visible or palpable. Calcified cysticerci may be visualised using ultrasound, CT scan or MRI.

Incubation period

Symptoms of cysticercosis may appear from weeks to years after infection. Eggs appear in the faeces 8–12 weeks after infection with the adult T. saginata tapeworm and after 10–14 weeks with T. solium.

Public health significance & occurrence

Taeniasis occurs worldwide. It is commonly seen in parts of Latin America, Africa, South East Asia and Eastern Europe. Both forms are usually imported to Australia but sporadic locally acquired cases of T. saginata infection have been reported.

Many infections are largely asymptomatic, but the larval stage of T. solium may cause fatal cysticercosis. Chronic tapeworm infections contribute to malnutrition for developing communities in many parts of the world.

Reservoir

Humans are the definitive host for both species. Cattle are the intermediate host for T. saginata and pigs for T. solium.

Mode of transmission

Eggs of T. saginata passed in the faeces of an infected person are only infectious to cattle. Humans are infected by ingestion of raw or undercooked beef infected with cysticerci bovis, the larval stage of T. saginata. In humans the adult tapeworm develops in the intestine over two to three months. The cycle of infection repeats when infectious eggs are passed in the faeces and later ingested by cattle, slowly migrating into the flesh and transforming into the larval stage.

Infections by T. solium may follow a similar cycle with consumption of infected pork leading to the subsequent development of adult tapeworms. However human infection may also occur through the consumption of T. solium eggs. This occurs by direct transfer from the faeces of an infected person or through the ingestion of contaminated food or water. When the eggs of T. solium are ingested by either humans or pigs the embryos escape the shells and penetrate the intestinal wall, with subsequent spread of larvae to various tissues to produce cysticercosis.

Period of communicability

T. saginata is not directly transmissible from person to person although T. solium may be. Adult tapeworms may persist in the intestines for up to 30 years and are able to disseminate eggs for all of this time. Eggs may remain viable in the environment for months.

Susceptibility & resistance

Everyone is susceptible to infection. Infection does not appear to confer immunity.

Control measures

Preventive measures
The public should be advised to avoid faecal contamination of soil, and human and animal food; avoid the use of raw sewage for irrigation of pasture soil; and to cook beef and pork thoroughly.

Beef and pork, should be adequately cooked, for example at 60°C for five minutes.

Freezing meat below –5°C for more than four days will kill cysticerci.

Meat should be routinely inspected for evidence of taeniasis at slaughter.

Control of case
Praziquantel or niclosamide are used for treatment of beef and pork tapeworm infections. Consult the current version of Therapeutic guidelines: antibiotic (Therapeutic Guidelines Limited).

Persons harbouring adult T. solium should be immediately identified and treated to prevent human cysticercosis. For cysticercosis surgical intervention may relieve symptoms. For CNS cysticercosis, praziquantel or albendazole may be used, with corticosteroids if indicated.

Isolation is not required. The case and relevant caregivers should be advised that the case’s faeces may be infectious and advised on sanitary disposal of wastes.

Control of contacts
Symptomatic patients exposed to a suspected source of infection should be evaluated for evidence of taeniasis.

Control of environment
If the history is consistent with local infection the source of the infection should be investigated, often with the assistance of the local government.

Outbreak measures

Not applicable.

Additional sources of information

Centers for Disease Control and Prevention
www.dpd.cdc.gov

Infectious diseasesepidemiology and surveillance