TAENIA SOLIUM (Pork tapeworm)

GEOGRAPHICAL DISTRIBUTION

The infection is prevalent in places where pork or pork products are eaten raw or under-cooked. It is common in East Europe, South and Central America, South Africa, China, India, Korea and Indonesia.

LOCATION IN HOST

The scolex is attached to the mucosa of the jejunum with the rest of the strobila in the intestinal lumen.

MORPHOLOGY

The scolex has a rostellum with two rows of hooks. The segments are similar to those of Taenia saginata. Mature segments are roughly square in shape. Gravid segments have less than 13 primary uterine branches as oppose to the Taenia saginata, which the number of uterine segments are more than 13.

LIFE CYCLE

Man is the only definitive host whereas pig is the only intermediate host. Life cycle is similar to that of Taenia saginata. The larval stage in the pig muscle is called Cysticercus cellulosae. Human infection occurs when pork containing Cysticercus cellulosae is eaten raw or under-cooked.

CLINICAL FEATURES

Clinical features are similar to those of Taenia saginata. Often the infection is asymptomatic except noticing whitish segments in faeces or experience of segments actively moving out of the anus. Vague abdominal symptoms such as pain, nausea, weight loss and anorexia may be present. In some the symptoms are relieved by ingestion of food.

COMPLICATIONS

Unlike in Taenia saginata, if an individual ingests eggs (usually accidentally) life cycle will continue as in the intermediate host, pig. Therefore humans can develop Cysticercosis, a complication due to the presence of pork worm larvae (Cysticercus cellulosae) in the skeletal muscles.

DIAGNOSIS

This is also similar to that of Taenia saginata.

1. The gravid segments passed in the faeces could be injected with Indian ink to show the lateral uterine branches of the uterus. In Taenia solium there are less than 13 primary branches of the uterus (compare with Taenia saginata).

2. If the scolex is passed following treatment, presence of hooks distinguishes it from Taenia saginata

3. If the gravid segments are ruptured eggs may be found in faeces (taenid egg).

EPIDEMIOLOGY

Prevalence of the infection is lower than that of beef tape worm infection. This is because some communities do not eat pork and in others when pork is eaten it is usually well cooked. While Taenia saginata infection occurs both in highly develop and developing countries, Taenia solium infection and its major complication, Cysticercosis, are prevalent in poor communities in which people live in close contact with pigs and eat improperly cooked pork. Uncooked or partially cooked pork products can transmit the infection.

PREVENTION AND CONTROL

Thorough cooking of pork is very important. Heating meat to 50ºC kills the cysticerci but those in the inside of large pieces may not reach the require temperature. At 0ºC the cysticerci can live for 70 days. Freezing at -10ºC for 4 days kills the cysticerci.

TREATMENT

A single dose of praziquantel (10 mg/kg) is highly effective. Niclosamide can also be given. The dose is 2gm for adults and lower doses for the children. The tablets are chewed and washed down with a little water.