Cysticercosis – Transmission, Diagnosis, and Prevention

What is Cysticercosis?

Cysticercosis is a parasitic tissue infection caused by larval cysts of the tapeworm Taenia solium. These larval cysts infect brain, muscle, or other tissue, and are a major cause of adult-onset seizures in most low-income countries. A person gets cysticercosis by swallowing eggs found in the feces of a person who has an intestinal tapeworm.  People living in the same household with someone who has a tapeworm have a much higher risk of getting cysticercosis than people who don’t. People do not get cysticercosis by eating undercooked pork.  Eating undercooked pork can result in intestinal tapeworm if the pork contains larval cysts.  Pigs become infected by eating tapeworm eggs in the feces of a human infected with a tapeworm.

Both the tapeworm infection, also known as taeniasis, and cysticercosis occur globally. The highest rates of infection are found in areas of Latin America, Asia, and Africa that have poor sanitation and free-ranging pigs that have access to human feces. Although uncommon, cysticercosis can occur in people who have never travelled outside of the United States. For example, a person infected with a tapeworm who does not wash his or her hands might accidentally contaminate food with tapeworm eggs while preparing it for others.

How does cysticercosis spread?

Cysticercosis spreads through the poop of someone infected with the adult tapeworm T. solium. T. solium lays its eggs in human intestines and then the eggs leave your body in your poop. You get cysticercosis from ingesting something that’s contaminated by poop carrying these eggs.

Poop can get into soil, water, plant material and the food we eat. You can accidentally ingest T. solium eggs after coming in contact with something that’s contaminated, such as:

• Drinking water that hasn’t been boiled or treated.
• Eating unwashed fruits or vegetables.
• Touching your mouth or eating after using the bathroom or touching poop.

You don’t get cysticercosis from eating undercooked pork.

What causes cysticercosis?

An infection with eggs of the parasite T. solium causes cysticercosis. You can get cysticercosis by eating or drinking something that has T. solium eggs on it (like unwashed fruits and vegetables or untreated water) or by touching your mouth after touching something with T. solium eggs in it (like poop or something contaminated with poop).

The eggs hatch in your intestines, and young T. solium worms move out into the tissues of your body and form sacs (cysts). These cysts usually don’t cause symptoms unless there are a lot of them in one place. You can have them for weeks to years without knowing it. Your immune system responds when the cysts die, causing symptoms.

What are risk factors?

Risk factors associated with acquiring cysticercosis include living in areas where the parasite is endemic (most commonly in rural developing countries where pigs roam freely and come into contact with human feces), drinking water or eating food contaminated with tapeworm eggs, and living in a household where another family member has intestinal tapeworm infection (taeniasis). Individuals who have taeniasis and poor hygiene are also at increased risk of infecting themselves.

What are cysticercosis symptoms and signs?

The symptoms will depend on the location and the number of cysticerci, though many individuals with cysticercosis will never develop any symptoms at all. The majority of patients with cysticercosis who present to a health care professional have central nervous system involvement (neurocysticercosis or NCC). Symptoms of neurocysticercosis may include the following:

• Nausea and vomiting, abdominal pain
• Headache
• Lethargy
• Confusion
• Vision changes
• Balance problems
• Weakness or numbness
• Seizure (often the presenting symptom, occurs in about 70% of people with NCC)

Involvement of other body tissues may cause skeletal muscle swelling, subcutaneous cysts, and vision changes from cysts infecting the eyes.

Possible Complications

Complications may include:

• Blindness, decreased vision
• Heart failure or abnormal heart rhythm
• Hydrocephalus (fluid buildup in part of the brain, often with increased pressure)
• Seizures

Cysticercosis Diagnosis

The diagnosis is fairly simple and the doctor will ask for the following tests:

Stool analysis: Doctors and labs may ask for more than one stool sample to check for the presence of tapeworm eggs and the extent of infection.

Blood sample: Once the infection has invaded tissues, doctors will ask for a blood sample to check antibodies in the blood which definitely indicate presence of infection.

Imaging tests: A CT scan or MRI, X-ray or an Ultrasound is required to confirm invasive tapeworm infection and the presence of cysts.

Treatment

Once diagnosed with infection, doctors usually prescribe oral medicines to kill the tapeworm presence including larvae and follow it up with a stool examination which should not have tapeworm, larva or proglottids to double check that one is clear of the infection.

The effect of oral medications prescribed depends a lot on the type of tapeworm infection detected and the site of infection. The idea is to not re-infect oneself and therefore, hand sanitation and hygiene becomes very important.

Treatment for invasive tapeworm infection also depends on the type of tapeworm detected and the extent and site of infection- anthelminthic drugs, anti-inflammatory therapy, anti-epileptic therapy, shunt placement and surgery.

Neurocysticercosis treatment should be based on each individual and whether cysts are nonviable or active, which usually can be assessed by neuroimaging studies such as MRI or CT, and where they are located.

For patients with only nonviable cysts, treatment should be indicative and contain anticonvulsants for individuals with seizures and shunting for patients with hydrocephalus.

Corticosteroids are specified for all patients with multiple cysts and associated cerebral edema (“cysticercal encephalitis”). Hydrocephalus shunting is also important.

Ocular cysticercosis also is attended to by surgical elimination of the cysts, but not generally with antihelmintihc drugs, which could exacerbate ocular inflammation.

How to Prevent Cysticercosis?

• Avoid eating meat. While pork is the prime culprit for spreading solium, their eggs can also be found on meat that was stored or transported alongside pork. Meat infested with pork tapeworms cannot lead directly to cysticercosis, but it can lead to taeniasis, a tapeworm infection of the gut.
• Use caution in high-risk areas. In the U.S., the most common areas for cysticercosis infection are California, Arizona, and Texas. In Europe, most cases are reported in Spain and Portugal. The disease is more widespread in Asia, Latin America, and Africa, where farms often do not adhere to strict sanitation guidelines and rates of infection are highest.
• Wash and peel your fruits and vegetables. Washing your produce thoroughly will remove Taenia solium larvae that cause cysticercosis. Place your produce beneath cool, flowing tap water. Move the fruit or vegetable slowly around beneath the tap so that the entire surface is washed.
• Wash your hands frequently. The importance of washing your hands when trying to prevent fecal-oral contamination cannot be overstated. Use an antibacterial soap and scrub for at least twenty seconds. Be sure to scrub the backs of your hands and between your fingers in addition to washing your palms.
• Drink clean water. Because solium can be found in local water supplies, bottled or boiled water is the way to go when trying to avoid cysticercosis. If you boil water, let it boil for at least one minute before letting it cool to a drinkable temperature. Alternately, use an “absolute 1 micron or less” filter and dissolve iodine tablets in the water after filtering it.