Cysticercosis- Clinical manifestations, diagnosis, treatment
Cysticercosis is a parasitic infection caused by the larval stage of the pork tapeworm, Taenia solium. The infection occurs when humans accidentally ingest the eggs of the tapeworm, which are shed in the feces of infected humans or pigs. The eggs hatch in the intestine and release larvae that migrate through the bloodstream and lodge in various tissues, such as the brain, muscles, eyes, and skin. There they form cysts (also called cysticerci) that can cause a variety of symptoms depending on their location and number.
Cysticercosis is a major public health problem in many parts of the world, especially in low- and middle-income countries where sanitation is poor and pigs are raised in close contact with humans. It is estimated that about 50 million people are infected with T. solium worldwide, and that cysticercosis causes about 50,000 deaths per year. Cysticercosis is also an emerging disease in some developed countries due to increased immigration and travel from endemic areas.
The most serious and common form of cysticercosis is neurocysticercosis (NCC), which affects the central nervous system. NCC is the leading cause of acquired epilepsy in many endemic regions, accounting for up to 70% of cases. NCC can also cause headaches, hydrocephalus, meningitis, stroke, dementia, and other neurological disorders. NCC can be fatal if not treated promptly and adequately.
Other forms of cysticercosis include ocular cysticercosis, which can impair vision or cause blindness; subcutaneous cysticercosis, which can produce painless nodules under the skin; and muscular cysticercosis, which can cause muscle weakness or pain. Cysticercosis can also affect other organs such as the heart, liver, lungs, and spleen.
The diagnosis of cysticercosis is based on a combination of clinical, epidemiological, radiological, and serological criteria. The treatment of cysticercosis depends on the type, location, and number of cysts, as well as the patient`s clinical condition. The main options are antiparasitic drugs (such as praziquantel or albendazole), corticosteroids (to reduce inflammation), antiepileptic drugs (to control seizures), surgery (to remove cysts or relieve pressure), and supportive care.
The prevention and control of cysticercosis require a comprehensive approach that involves breaking the cycle of transmission between humans and pigs. This includes improving sanitation and hygiene practices; ensuring proper cooking of pork; treating human tapeworm carriers with anthelmintics; vaccinating pigs against T. solium infection; and educating communities about the risks and prevention of cysticercosis.
The symptoms of cysticercosis depend on where the cysts form in the body, how many cysts are present, and what stage they are in. Cysts can develop in various tissues, such as the brain, spinal cord, eyes, muscles, and skin. The most common and serious form of cysticercosis is neurocysticercosis, which affects the central nervous system.
The incubation period of cysticercosis is variable, ranging from several months to many years. Some people may remain asymptomatic for a long time, while others may develop symptoms when the cysts start dying and cause inflammation. The following are some of the possible clinical manifestations of cysticercosis according to the site of infection:
- Subcutaneous cysticercosis: This form of cysticercosis presents as small, movable, painless nodules under the skin that are commonly noticed in the arms or chest. After a few months or years, the nodules may become swollen, tender, and inflamed, and then they gradually disappear.
- Muscular cysticercosis: This form of cysticercosis appears as dot-shaped or ellipsoidal calcifications in the muscles that can be detected by radiography. There are three types of clinical manifestations depending on the pathogenesis: the myalgic type (muscle pain), the mass-like or pseudotumor type (muscle swelling or lump), and the rare pseudohypertrophic type (muscle enlargement).
- Neurocysticercosis: This is the most common and serious form of cysticercosis that affects the brain and spinal cord. It is observed in 60-90% of infected patients and is endemic in many parts of the developing world. Cysts localized within the brain may range from 4-20 mm in length and cause different neurological complications depending on their location, number, size, and stage. Seizures and headaches are the most common symptoms of neurocysticercosis and occur in 70-90% of infected patients. Other symptoms may include dizziness, involuntary muscle movement, intracranial hypertension, dementia, hydrocephalus (excess fluid around the brain), psychiatric disturbances, meningoencephalitis (inflammation of the brain and meninges), transient paresis (weakness), behavioral disorders aphasia (language impairment), and visual disturbances. Neurocysticercosis is considered the second most common cause of intracranial space-occupying lesion (ICSOL) after tuberculosis in India.
- Ocular cysticercosis: This form of cysticercosis affects the eyes and is present in 20% of cases. Cysts can be found in the vitreous humor (the clear gel that fills the eye), subretinal space (the space between the retina and the choroid), and conjunctiva (the thin membrane that covers the white part of the eye). The condition may present as blurred vision or loss of vision, iritis (inflammation of the iris), uveitis (inflammation of the uvea), and palpebral conjunctivitis (inflammation of the eyelid). In extreme cases, the infection may cause complete detachment of the retina.
The diagnosis of cysticercosis is usually based on a combination of clinical presentation, abnormal findings on neuroimaging and serology (blood test like an immunoblot assay), and occasionally with a biopsy. The following are some of the methods used to diagnose cysticercosis:
- Microscopy: A definitive diagnosis of cysticercosis can be made by biopsy of the lesion and its microscopic examination to show the invaginated scolex with suckers and hooks. However, this method is invasive and not always feasible.
- Imaging methods: Radiological techniques such as X-ray, computed tomography (CT) scan, and magnetic resonance imaging (MRI) scan can detect calcified or non-calcified cysts in various tissues, especially in the brain and muscles. X-ray can show dot-shaped or ellipsoidal calcifications in subcutaneous tissue and muscles. CT scan can show small hypodensities (ring or disc-like) with a bright central spot in the brain. MRI scan can show noncalcified cysts and ventricular cysts better than CT scan. However, these methods are expensive and not widely available in endemic areas.
- Serology: Serological tests can detect anticysticercus antibodies or antigens in serum or cerebrospinal fluid (CSF). Antibody detection can be done by enzyme-linked immunosorbent assay (ELISA) or enzyme-linked immunoelectrotransfer blot (EITB) tests. EITB is more sensitive and specific than ELISA, especially when using an affinity-purified lentil-lectin glycoprotein fraction (LLGP) as antigen. However, EITB is not effective in detecting antibodies when only one cyst is present. Antigen detection can be done by ELISA or indirect immunofluorescence assay (IFA) using monoclonal antibodies. Antigen detection indicates recent or viable infection.
- DNA detection: Molecular methods such as polymerase chain reaction (PCR) can amplify specific DNA sequences of T. solium from CSF or biopsy samples. PCR can be based on repetitive DNA, ribosomal DNA, mitochondrial DNA, or antigen 2 (Ag2) gene. PCR has high sensitivity and specificity in neurocysticercosis diagnosis.
- Others: Ocular cysticercosis can be diagnosed by ophthalmoscopy, which can show cysts in the vitreous humor, subretinal space, or conjunctiva. Eosinophilia may occur in the early stage of cysticercosis but is not constant. CSF analysis may show elevated protein level, lymphocytosis, and low glucose level in neurocysticercosis.
The treatment of cysticercosis depends on the location, number, and stage of the cysts in the body, as well as the symptoms and complications of the infection. Some people with cysticercosis do not need any specific treatment, while others may require medications, surgery, or both.
The most commonly used medications for cysticercosis are antiparasitic drugs, corticosteroids, and antiepileptic drugs.
- Antiparasitic drugs: These drugs are used to kill the cysts and prevent their growth and spread. The two main antiparasitic drugs for cysticercosis are praziquantel and albendazole. They are usually given for several weeks or months, depending on the severity and type of infection. However, these drugs may also cause inflammation and damage to the surrounding tissues as the cysts die. Therefore, they are not recommended for people with eye or spinal cord cysts, or for people with only calcified (dead) cysts in the brain.
- Corticosteroids: These drugs are used to reduce the inflammation and swelling caused by the dying cysts or by the immune system`s reaction to the infection. They are often given along with antiparasitic drugs or before surgery to prevent or treat complications such as seizures, headaches, hydrocephalus, or brain edema.
- Antiepileptic drugs: These drugs are used to control seizures that may occur due to neurocysticercosis. They are usually given for a long-term basis, even after the cysts are cleared, to prevent recurrence of seizures.
Surgery may be needed for some cases of cysticercosis, especially when the cysts are located in the eye, spinal cord, ventricles (fluid-filled spaces) of the brain, or when they cause severe symptoms or complications that do not respond to medications. Surgery may involve removing the cysts or draining the excess fluid from the brain (shunt surgery). Surgery may also be combined with antiparasitic and anti-inflammatory medications to improve the outcome.
The prognosis of cysticercosis varies depending on the location, number, and stage of the cysts, as well as the response to treatment and the occurrence of complications. In general, people with subcutaneous or muscular cysticercosis have a good prognosis and may recover without treatment. People with ocular cysticercosis may have a good prognosis if the cysts are removed early and do not cause permanent damage to the eye. People with neurocysticercosis may have a variable prognosis depending on the severity and type of infection. Some people may have mild or no symptoms and recover completely with treatment, while others may have severe or recurrent symptoms and develop long-term complications such as epilepsy, cognitive impairment, hydrocephalus, or death.
Cysticercosis is a preventable disease that can be avoided by following some simple measures of hygiene and sanitation. The main strategies for preventing cysticercosis are:
- Breaking the cycle of transmission between humans and pigs. This can be achieved by:
- Treating people who have intestinal tapeworm infection with praziquantel or niclosamide to eliminate the adult worms and prevent the shedding of eggs in feces.
- Providing adequate sanitation facilities and promoting safe disposal of human feces to prevent environmental contamination with tapeworm eggs.
- Restricting the access of pigs to human feces and providing them with clean water and feed.
- Inspecting pork for cysticerci at slaughterhouses and condemning infected meat.
- Freezing or cooking pork thoroughly before consumption to kill any cysticerci present.
- Educating the public about the risk factors and symptoms of cysticercosis. This can be done by:
- Raising awareness about the life cycle of T. solium and how it causes cysticercosis in humans and pigs.
- Encouraging people to seek medical attention if they have signs or symptoms of cysticercosis, such as seizures, headaches, vision problems, or skin nodules.
- Advising people to wash their hands with soap and water after using the toilet, changing diapers, and before handling food.
- Teaching children the importance of washing hands to prevent infection.
- Washing and peeling all raw vegetables and fruits before eating.
- Using good food and water safety practices while traveling in developing countries where cysticercosis is endemic.
- Vaccinating pigs against T. solium infection. This can be done by:
- Developing and distributing effective vaccines that induce short-term immunity in pigs against T. solium infection.
- Using recombinant vaccines that express oncosphere antigens such as TSOL18 and TSOL45 that have shown high protection rates in vaccine trials.
- Combining vaccination with deworming of pigs to reduce the parasite burden and transmission potential.
By implementing these prophylactic measures, cysticercosis can be controlled and eventually eliminated as a public health problem.
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