What is the cause?
It is caused by accidentally swallowing the eggs of pork tapeworm. Once inside the stomach, the tapeworm egg hatches, penetrates the intestine, travels through the bloodstream and may develop into cysticerci in the muscles, brain, or eyes. Tapeworm eggs are also passed out in the faeces of a person who is infected. These tapeworm eggs are spread through food, water, or surfaces contaminated with faeces. This can happen by ingesting contaminated food or water, or putting contaminated fingers in the mouth. A person who has tapeworm infection can reinfect himself (autoinfection).
What are the symptoms?
Signs and symptoms depends on the location and number of cysticerci in the body.
- Neurocysticercosis (cysticerci in the brain or spinal cord):
Symptoms of neurocysticercosis depend upon where and how many cysticerci (often called lesions) are there in the brain. Seizures, and headaches are the most common symptoms. However confusion, lack of attention, difficulty with balance and swelling of the brain (called hydrocephalus) may also occur.
Symptoms can occur months to years after infection, usually when the cysts are in the process of dying. When this happens, the brain swells in response to the antigens released from the cysticerci. The pressure caused by swelling is what causes most of the symptoms of neurocysticercosis.
- Cysticerci in the muscles:
Cysticerci in the muscles generally do not cause symptoms. However, these may be felt or seen as lumps under the skin in superficial muscles.
- Cysticerci in the eyes:
Although rare, cysticerci may float in the eye and cause blurry or disturbed vision. Infection in the eyes may cause swelling or detachment of the retina.
How is it diagnosed?
Diagnosis can be difficult and may require several testing methods. The doctor asks about where one has travelled and eating habits. Diagnosis of neurocysticercosis is usually made by MRI or CT scans of the brain. Blood tests are available to look for antibodies against the cysticerci and may help diagnose an infection.
What is the treatment?
Infections are generally treated with anti-parasitic drugs in combination with anti-inflammatory drugs. Surgery is sometimes necessary to treat cases in the eyes, cases that are not responsive to drug treatment, or to reduce brain edema (swelling). Not all cases of cysticercosis are treated.
Often, the decision of whether or not to treat neurocysticercosis is based upon the number of lesions found and the symptoms. When only one lesion is found, often treatment is not given. If one has more than one lesion, specific anti-parasitic treatment is generally recommended.
If the brain lesion is considered calcified (this means that a hard shell has formed around the tapeworm larvae), the cysticerci is considered dead and specific anti-parasitic treatment is not beneficial. As the cysticerci die, the lesion shrinks. The swelling goes down, and often symptoms (such as seizures) go away.
Can infection be spread from person to person?
Cysticerci is not spread from person to person. However, a person infected with the intestinal tapeworm stage of the infection sheds tapeworm eggs in their bowel movements. Tapeworm eggs that are accidentally swallowed by another person can cause infection.
What is the prevention?
- Avoid eating raw or undercooked pork and other meats
- Do not eat meat of pigs that are likely to be infected with the tapeworm
- Wash hands with soap and water after using the toilet and before handling food, especially when travelling in developing countries
- Wash and peel all raw vegetables and fruits before eating. Avoid food that may be contaminated with faeces
- Avoid soft drinks and ice cubes
- Boiled water is the safest option where the quality of drinking water is suspect
What is cysticercosis?
Cysticercosis is an infection caused by the pork tapeworm, Taenia solium. Infection occurs when the tapeworm larvae enter the body and form cysticerci. When cysticerci are found in the brain, the condition is called neurocysticercosis.
Where is cysticercosis found?
The tapeworm that causes cysticercosis is found worldwide. Infection is found most often in rural, developing countries with poor hygiene where pigs are allowed to roam freely and injest human faeces. This allows the tapeworm infection to be completed and the cycle to continue.
Humans are the definitive T solium hosts and can carry an intestinal adult tapeworm. Intermittent faecal shedding of egg-containing free T solium ensues, with the intention that the intermediate host (normally pigs) will ingest the excreted eggs in contaminated food or water. T solium embryos penetrate the GI mucosa of the pig and are disseminated to peripheral tissues with resultant formation of larval cysts (cysticerci). When undercooked pork is consumed, an intestinal tapeworm will again be formed, completing the life cycle of the worm. Human cysticercosis occurs when T solium eggs are ingested via faecal-oral transmission from a tapeworm host. The human then becomes an accidental intermediate host, with development of cysticerci within organs.