Essentials of Diagnosis
- Surgical excision of involved tissue, with microscopic identification of parasite.
- Frequently calcified cysts present on x-ray or computed tomography (CT) scans.
- Positive serology indicating previous exposure to T solium.
- Fine-needle aspiration of cysts (characteristic cytomorphology).
General Considerations
Cysticercosis is caused by invasion of tissue by the larval forms of T solium, which have been referred to as Cysticercus cellulosea, although the name is not taxonomically correct and introduces confusion. Within a host infected by the adult T solium, eggs or proglottids are passed in the stool. Once eggs or proglottids are ingested by either pigs (intermediate hosts) or humans (definitive and intermediate hosts), eggs hatch in the gastric juice, allowing the cysticercus to migrate from the intestine to disseminated sites, via efferent mesenteric venules. Autoinfection may also occur in humans, wherein eggs produced by the adult intestinal worm hatch and invade the intestinal epithelium.
Cysticercosis is an important parasitic disease in Canada, particularly in regions with immigrant populations from areas where Taenia solium (the pork tapeworm) is endemic. Though rare in the general population, it can still occur, especially when hygienic practices and access to proper sanitation are insufficient.
Cysticercosis is considered rare in Canada due to the strong public health measures, such as food safety regulations and sanitation practices. However, cases can still be seen in individuals who have traveled to or immigrated from endemic areas like parts of Latin America, Asia, and sub-Saharan Africa. According to the Public Health Agency of Canada, neurocysticercosis remains a significant cause of acquired epilepsy in immigrant populations. Reports from the Canadian Journal of Infectious Diseases and Medical Microbiology suggest that the incidence of neurocysticercosis is rising, albeit slowly, in Canada, especially in individuals from high-risk countries.
Clinical Findings
Signs and Symptoms
The symptoms associated with cysticercosis relate to the organ that is invaded by cysticerci and to the inflammatory reaction that occurs in response to the larva. Within the brain, cysticercosis may cause arachnoiditis or chronic meningitis, with associated headache, vertigo, vomiting, and cranial neuropathies. Alternate presentations include obstructive hydrocephalus with ataxia and dementia, intracranial vasculitis with focal neurologic signs and neuropsychiatric changes, or mass effect with seizures, headache, or focal neurologic deficits. In addition, cord compression with lower limb weakness and loss of bowel and bladder continence may occur. Cysts outside the central nervous system tend to occur within muscle, are most often asymptomatic, and eventually die, calcify, and may be incidentally detected on radiographs. Occasionally, muscle cysts will cause pseudohypertrophy that may be associated with myositis, high fever, and eosinophilia. Cysts may also occur within critical organs (commonly heart and liver) where they present as mass lesions with pain or obstructive symptoms.
Laboratory Findings
Patients with cysticercosis may have a mild elevation on leukocyte count, possibly with eosinophilia. In patients with meningitis associated with neurocysticercosis, cerebrospinal fluid examination may show either lymphocytic or eosinophilic pleocytosis, hypoglycorrhachia, and elevated protein. Recently a serologic test for T solium has been developed, but its performance characteristics remain to be validated. False positive results have been associated with infections caused by other cestodes. A negative serologic test does not exclude the diagnosis of cysticercosis.
Imaging
Living cysts associated with cysticercosis are often multiple and have a characteristic appearance on CT scans or magnetic resonance images, both enhancing and nonenhancing unilocular cysts. Patients with extraneurologic cysticercosis may have painless subcutaneous nodules, often on the shins, which are calcified and have a characteristic appearance on plain radiographs.
Differential Diagnosis
Patients who seek care for symptoms of infection with T solium most commonly do so because of the neurologic symptoms associated with neurocysticercosis. The most common neurologic symptoms are mass effect and seizures (related to intraparenchymal lesions), hydrocephalus (related to intraventricular cysts), chronic meningitis (related to subarachnoid cysts), and cord compression (owing to spinal cord cysts). The differential diagnosis of each of these symptoms is beyond the scope of this discussion, but malignancy may present in identical ways, and so it must be ruled out.
Canadian doctors rely on imaging techniques such as CT scans and MRIs, and often use serological tests, though these are not always conclusive.
Complications
Visceral cysticercosis is also commonly asymptomatic, but may obstruct local structures (eg, biliary obstruction in hepatic cysticercosis). Neurocysticercosis may lead to permanent neurologic impairment, coma, or even death.
The risk of complications such as epilepsy, meningitis, or even death remains a concern, particularly in cases of neurocysticercosis. In fact, neurocysticercosis is one of the leading causes of acquired epilepsy in individuals from endemic regions. Hospitals in Canada, such as the Toronto General Hospital and McGill University Health Centre, are equipped with the latest technologies to diagnose and manage such cases effectively.
Treatment
Therapy for cysticercosis includes surgery when feasible and necessary, in combination with praziquantel or albendazole (see Box 2). Therapy of cysticercosis commonly increases the local inflammation, thereby transiently causing a paradoxical worsening of the patient’s symptoms. Whether corticosteroids should be used as adjunctive therapy for patients being treated for neurocysticercosis remains in debate.
The approach to treatment in Canada follows international guidelines, with antiparasitic medications such as albendazole or praziquantel being used, in addition to surgical excision when necessary. Canadian health authorities, including the Canadian Agency for Drugs and Technologies in Health (CADTH), recommend the use of corticosteroids in specific cases to reduce inflammation, though clinical guidelines can vary.
Prognosis
The mortality rate for untreated neurocysticercosis approaches 50%, but treatment decreases this rate to 5-15%.
The prognosis for cysticercosis in Canada varies depending on the location and severity of cysts. With proper treatment, the mortality rate can be significantly reduced. However, if left untreated, the condition can lead to permanent neurological damage or death. Studies have shown that with early intervention and appropriate care, most Canadian patients can recover fully, especially when the disease is diagnosed early.
Prevention & Control
Guidelines for the prevention of cysticercosis are the same as for the prevention of T solium infection (Box 3).
Preventing cysticercosis in Canada largely revolves around controlling pork consumption and ensuring that pork is properly cooked, as well as ensuring proper sanitation to avoid contamination of food and water supplies. Education and awareness campaigns, particularly among immigrant populations from endemic regions, play a critical role in reducing the risk of transmission. Public Health Canada offers guidelines on controlling foodborne diseases, including those caused by parasitic infections.