Cysticercus IgG

Cysticercus is the larval stage of Taenia solium (pork tapeworm) and the causative agent of cysticercosis, a parasitic tissue infection that primarily affects the central nervous system (CNS), muscles, and subcutaneous tissues. 

When cysticerci invade the brain, the condition is known as neurocysticercosis (NCC), a leading cause of adult-onset epilepsy in endemic regions worldwide.

What is Cysticercus?

Cysticercus is the larval stage of Taenia solium (pork tapeworm) and the cause of cysticercosis, a parasitic tissue infection that affects both humans and pigs. Humans acquire cysticercosis by ingesting T. solium eggs through contaminated food, water, or poor hygiene. 

The central nervous system (CNS) is the most commonly affected site, leading to neurocysticercosis (NCC), a major cause of adult-onset epilepsy in endemic regions.

Clinical Manifestations

Neurocysticercosis presents in two primary forms: parenchymal and extraparenchymal. 

In parenchymal NCC, cysticerci lodge in the brain parenchyma, with seizures occurring in 50 to 80 percent of cases. 

Extraparenchymal NCC involves cysts in the ventricles, subarachnoid space, spinal cord, or eyes, leading to complications such as hydrocephalus, intracranial hypertension, stroke, or vision loss. 

In addition to CNS involvement, cysticercosis can affect muscle and subcutaneous tissue, often appearing as painless nodules on the arms or chest. These nodules, also called subcutaneous cysticerci, may remain asymptomatic but can sometimes be associated with muscle inflammation or pseudohypertrophy.

Diagnosis

Neuroimaging is the gold standard for diagnosing cysticercosis. CT scans are effective in detecting calcified cysts, hydrocephalus, and perilesional edema, whereas MRI is superior for identifying viable cysts and lesions in the ventricular or subarachnoid spaces. 

Serological tests are highly specific for detecting viable cysticercosis, while ELISA-based antigen detection can help identify active infections, although its specificity is lower than immunoblot testing. 

Cerebrospinal fluid (CSF) analysis may show eosinophilia, particularly in subarachnoid disease.

Treatment & Management

In 2021 the World Health Organization released guidelines on the management of cystercosis.

Management of cysticercosis depends on cyst viability and location. Viable parenchymal cysts are treated with albendazole (15 mg/kg/day) or praziquantel (50 mg/kg/day), typically with corticosteroids to reduce inflammation. Seizure control with antiepileptic drugs is essential. 

Extraparenchymal NCC often requires surgery, particularly for ventricular cysts causing hydrocephalus, with neuroendoscopic removal or CSF shunting as common interventions. 

Subarachnoid NCC may need prolonged antiparasitic therapy with high-dose corticosteroids, while ocular cysts require surgical removal to prevent retinal damage.

Antiparasitic therapy is contraindicated for calcified cysts, as they are inactive and provide no treatment benefit. 

Antiparasitic therapy is also contraindicated in severe encephalitis or high cyst burden, as it may trigger excessive inflammation, risking cerebral edema or stroke.

Epidemiology & Prevention

Cysticercosis affects 50 to 100 million people worldwide and remains a leading cause of epilepsy in endemic regions. 

It is most prevalent in Latin America, Africa, India, China, and Southeast Asia. Due to immigration from endemic areas, cases are increasingly recognized in the United States, particularly in Texas, California, and the Southwest.

Prevention focuses on hygiene, proper pork cooking, and treating tapeworm carriers. Handwashing and sanitation prevent fecal-oral transmission, while cooking pork eliminates cysticerci. In endemic areas, mass deworming, pig vaccination, and livestock antiparasitics help reduce transmission.

What is Cysticercus IgG?

Cysticercus IgG is a type of antibody produced by the immune system against Cysticercus larvae. 

These antibodies remain detectable long after the infection resolves, serving as markers of past or present infection.

While IgG antibodies to Cysticercus can be present in both active and past infections, their presence alone does not confirm active disease. 

Who Should Get Cysticercus IgG Tested?

Testing for Cysticercus IgG is recommended for individuals at risk of Taenia solium infection, particularly those with potential exposure or symptoms suggestive of neurocysticercosis (NCC).

• Individuals with neurological symptoms: seizures, chronic headaches, or signs of increased intracranial pressure may indicate neurocysticercosis, warranting IgG testing.
• Residents or travelers in endemic regions: those who have lived in or traveled to areas with high rates of T. solium transmission—such as Latin America, sub-Saharan Africa, and Asia—are at higher risk.
• Patients with suspected parasitic infections: if clinical findings or neuroimaging reveal cystic brain lesions, Cysticercus IgG testing can support a diagnosis of NCC.
• People with dietary or sanitation-related risk factors: individuals with a history of consuming undercooked pork or exposure to poor sanitation may have unknowingly ingested T. solium eggs, leading to cysticercosis.

Test Procedure and Interpretation

The following section outlines testing procedures and results interpretation for Cysticercus IgG:

Test Procedure and Preparation Requirements

Cysticercus IgG testing requires a blood sample, typically collected via venipuncture. The patient generally does not have specific preparation requirements, although it’s always important to confirm this with the ordering provider.

Normal Reference Ranges

Normal reference ranges for Cysticercus IgG may vary slightly depending on the laboratory performing the test. However, a negative result generally indicates no detectable immune response to Cysticercus at the time of testing. 

Positive results, especially in the context of clinical symptoms, suggest past or ongoing infection.

What Do High Levels of Cysticercus IgG Mean?

Elevated Cysticercus IgG levels indicate an immune response to T. solium larvae and are commonly associated with neurocysticercosis.

• Active or chronic infection: high IgG levels suggest the presence of viable or degenerating cysts, which may cause inflammation and neurological symptoms.
• Immune system response: IgG antibodies reflect prior or ongoing exposure to T. solium cysticerci. However, IgG antibody persistence can make it difficult to distinguish past from active infection.
• Potential need for treatment: patients with high IgG levels and clinical symptoms may require additional testing to confirm active infection, and subsequent antiparasitic therapy (albendazole or praziquantel) and adjunctive corticosteroids to control inflammation. 

What Do Low Levels of Cysticercus IgG Mean?

A low or negative Cysticercus IgG result does not always rule out neurocysticercosis, as antibody responses can vary. Low levels may be associated with the absence of cysticercosis, or they may indicate:

• Early-stage infection or low parasite burden: individuals with early or mild infections may not yet have mounted a detectable IgG response.
• Possible past infection with resolved immune response: some patients with prior exposure to T. solium may show reduced IgG levels over time, particularly if the infection has resolved.
• False negatives in immunocompromised individuals: patients with weakened immune systems (e.g., cancer or autoimmune patients, those with HIV, immunosuppressive therapy) may fail to generate a detectable IgG response despite active infection.

Need for additional diagnostic confirmation: if neurocysticercosis is still suspected, neuroimaging (MRI/CT) and cerebrospinal fluid (CSF) analysis should be performed to confirm the diagnosis.