It occurs when a person eats food; especially pork, contaminated with T. solim eggs (instead of larvae).
Cysticercosis is a rare infectious disease caused by the presence and accumulation of the larval cysts of a tapeworm (cestode) within the tissues of the body.
The scientific name for the tapeworm that causes cysticercosis is Taenia solium, also known as swine tapeworm.
Cysts of T. solium (cysticerci) can affect any area of the body, including the brain , a condition known as neurocysticercosis .
Symptoms vary from case to case. If cysticerci are located in the brain, central nervous system abnormalities can occur, most often seizures and headaches.
Cysticercosis can also affect the eyes, spinal cord, skin, and heart.
Causes of cysticercosis
Cysticercosis is due to ingestion of the eggs of the tapeworm known as Taenia solium.
Ingestion of contaminated pork generally results in an adult tapeworm infection and not in cysticercosis.
Life cycle of Tenia solium
The normal life cycle of pig tapeworms is as follows: the pig ingests tapeworm eggs, in the intestine of the pig, the eggs hatch and penetrate through the intestinal wall into muscle tissue.
There they encyst and develop into larval cysts called cysticerci.
When the pig dies and its meat is consumed by a person, the cysticerci are released and adhere to the wall of the intestine, where they develop into adult tapeworms that produce eggs.
This is known as an adult tapeworm infection and usually does not cause symptoms.
However, people with adult tapeworm infection can develop cysticercosis because they will release T. solium eggs through their feces and can ingest the eggs (autoinfection).
These people may also regurgitate or reflux the eggs of T. solium from the intestines to the stomach.
The eggs travel through the bloodstream and eventually make their way to muscle, subcutaneous tissue, the brain, and other tissues in the body.
After 60 to 90 days, the eggs develop into larval cysts (cysticerci).
Cysts remain in body tissue indefinitely, unable to move to the next stage in their life cycle.
As long as these larvae remain alive, they appear to be able to “disguise” themselves from the host’s immune system, causing only mild symptoms.
However, eventually the larvae die causing a strong defensive immune reaction against the surrounding cyst.
The cyst itself can become huge. These inflammatory reactions can cause serious illness, especially if cysticerci lodge in the central nervous system or in the heart.
The following conditions put you at great risk for taeniasis and cysticercosis:
Poor hygiene and sanitation
Lack of the habit of bathing and not washing your hands frequently and properly with soap and water exposes you to the consumption of contaminated matter that may contain tapeworm larvae or eggs.
Exposure to pigs
Those who have to deal with animals and human feces on farms are at great risk of contracting this infection.
Consumption of raw or undercooked meats
Undercooked meats do not kill the larvae or eggs of those that are contaminated, increasing the risk of infection.
Live or travel to endemic countries
Certain parts of Latin America, China, sub-Saharan Africa, and Southeast Asia are more prone to exposure to tapeworm infection where pigs roam freely.
If you live or travel to these places, it is very likely that you can get this infection.
Signs and symptoms of cysticercosis
Taeniasis due to T. solium is generally characterized by mild, nonspecific signs and symptoms.
6 to 8 weeks after ingestion of cysticerci, abdominal pain, nausea, diarrhea, or constipation may appear and last until the tapeworm dies after treatment (otherwise it may live for many years).
The symptoms of cysticercosis vary from case to case depending on the number and location of the cysticerci within the body.
Cysticerci are often found in muscle tissue. In some cases, the cysts have been located in the brain, eyes, or heart tissue.
Some people with cysticercosis will have no symptoms (asymptomatic) or very mild symptoms.
Many people with cysticercosis have central nervous system involvement (neurocysticercosis).
However, many people with neurocysticercosis do not have or develop symptoms, as the specific symptoms of neurocysticercosis depend on the number and location of the cysts involved, as well as the response of an individual’s immune system.
The four basic types of neurocysticercosis are parenchymal, subarachnoid, intraventricular, and spinal.
Symptoms common to all forms of neurocysticercosis include headaches, seizures, and accumulation of excess cerebrospinal fluid in the skull (hydrocephalus) that causes increased pressure on brain tissues.
This causes a variety of symptoms, such as headache, nausea, dizziness, vision changes, and vomiting.
In some cases, people who develop hydrocephalus often, in turn, develop swelling of the optic disc (papilledema) that can cause blurred or double vision.
Parenchymal disease can be associated with headaches, seizures, intellectual impairment, behavioral changes, and hydrocephalus.
Dysfunction of the ability to coordinate voluntary movements (ataxia) and muscle weakness on one side of the body (hemiparesis) can also occur with this form of neurocysticercosis.
Subarachnoid cysticercosis is associated with chronic inflammation of the membranes that cover the brain (meninges), headaches, seizures, and hydrocephalus.
Intraventricular cysticercosis can cause obstructive hydrocephalus.
A variant of this form of cysticercosis known as racemose cysticercosis can occur. Racemic cysticercosis is characterized by the accumulation of cysts at the base of the brain that can result in mental decline, coma, and life-threatening complications.
Cysts that affect the spinal cord are rare, but can cause meningitis or compression of the spinal cord.
In some cases, people can experience serious central nervous system infections, which can lead to life-threatening complications, such as a stroke or coma (cysticercal encephalitis).
People with severe infections of the central nervous system often first develop muscle pain (myalgia), weakness, and fever.
Ocular cysticercosis occurs when cysts form in the eyes. Associated symptoms may include eye pain, vision loss, and separation of the nerve-rich membrane that lines the eyes (retina) from its underlying supporting tissue (retinal detachment).
In some cases, cysticercosis can only affect the eyes (isolated ocular cysticercosis).
In some cases, cysts can form under the skin and cause small lumps. These lumps usually do not cause any additional symptoms.
The location of the infection that most often prompts a medical consultation is the brain, followed by the eye and surrounding tissues.
A diagnosis of cysticercosis can be made based on a complete clinical evaluation, a detailed history of the patient, and a variety of specialized tests.
The diagnosis is quite simple and the doctor will order the following tests:
Doctors and laboratories may request more than one stool sample to verify the presence of tapeworm eggs and the extent of the infection.
Once the infection has invaded the tissues, doctors will request a blood sample to check for antibodies in the blood that indicate the presence of an infection.
Neurocysticercosis treatment should be based on the individual and whether the cysts are not viable or active, which can usually be diagnosed by neuroimaging studies.
A CT or MRI scan, X-ray, or ultrasound is required to confirm invasive tapeworm infection and the presence of cysts.
In many cases, individuals with cysticercosis do not require treatment.
Once diagnosed with an infection, doctors often prescribe oral medications to eliminate the presence of tapeworms, including larvae, and perform a stool test that should be free of tapeworms, larvae, or proglottids to verify that there is no infection.
The effect of orally prescribed medications is highly dependent on the type of tapeworm infection and the site of infection.
The idea is not to get infected again and therefore sanitation and hand hygiene is very important.
Treatment for invasive tapeworm infection also depends on the type of tapeworm detected and the extent and site of the infection.
Anthelmintic medications, anti-inflammatory therapy, antiepileptic therapy, shunt placement, and surgery may be used.
For patients with only non-viable cysts, treatment should be indicative and contain anticonvulsants for individuals with seizures and shunts for patients with hydrocephalus.
Corticosteroids are specified for all patients with multiple cysts and associated cerebral edema (“cysticercal encephalitis”). Hydrocephalus is also important.
Ocular cysticercosis is also treated by surgical removal of the cysts, but not usually with anthelmintic medications, which could exacerbate eye inflammation.
Treatment of taeniasis may include the administration of:
- Praziquantel (5-10 mg / kg, single administration).
- Niclosamide (in adults and children over 6 years of age, in a dose of 2 g, single administration after a light breakfast, followed after 2 hours by a laxative, in children 2 to 6 years: 1 g, in children under 2 years: 500 mg).
Treatment of human cysticercosis is more challenging and may include prolonged treatments with praziquantel and / or albendazole, as well as supportive therapy with corticosteroids and / or antiepileptic drugs.
The antiparasitic drug albendazole was approved by the Food and Drug Administration (FDA) for the treatment of cysticercosis in 1996.
In severe cases, neurocysticercosis can be fatal and has been noted as a cause of death in Brazil and the United States.