Human sparganosis is a parasitic infection caused by the plerocercoid larvae (spargana) of Spirometra tapeworm. Infections are acquired by ingesting the raw or undercooked meat of snakes or frogs, drinking contaminated water with Spirometra larvae, or applying raw poultices to open wounds or mucous membranes. In the life cycle of Spirometra, humans are accidental hosts; dogs, cats, and other mammals are definitive hosts; freshwater crustaceans are the first intermediate hosts; and amphibians and reptiles are the second intermediate hosts.
The disease is most commonly found in East and Southeast Asia as a result of consuming infected raw snake, frog, or pig. In North America, sparganosis is endemic in animals, but human cases are rare. The most common cause for these cases is drinking contaminated water. The most prevalent species in Southeast Asia is Spirometra mansoni, while Spirometra mansonoides is predominant in the Western hemisphere.
Sparganosis is a rare infection. There are no obvious sex differences, and individuals of any age may be affected. Cerebral sparganosis most often occurs in adults. Most patients are from rural areas, and there does not seem to be a higher risk of infection among immunocompromised patients.
Symptoms of sparganosis depend upon the location where the sparganum invades. Once ingested, the parasite migrates, often asymptomatically, from the digestive system through the capillaries to diverse locations of the human body. The larvae most commonly affect subcutaneous tissues and muscles, eyes, the central nervous system, the genitourinary system, and visceral organs.
In the subcutaneous tissue, sparganosis forms a slowly growing nodule that can migrate, hence a "creeping tumor." Prolonged presence of the parasite provokes an infiltration of eosinophils, epithelioid cells, and lymphocytes. Erythema and edema develop around the parasite, causing discomfort, itchiness, and pain. If the spargana invade the eye, there can be inflammation and edema around the eye, leading to pain and vision changes. Invasion of the brain can lead to headaches, confusion, and seizures. In case of infection with Spirometra proliferum, the spargana may break up and invade many organs, which may lead to tissue damage, paralysis, blindness, and death.
The incubation period depends on the route of infection, but is usually 6-11 days. The life span of spargana is usually less than a year, but may be up to 20 years.
ICD10CM: B70.1 – Sparganosis
SNOMEDCT: 31659000 – Infection caused by Spirometra larvae
Differential Diagnosis & Pitfalls
A history of consuming raw or undercooked snake and frog may increase the priority of sparganosis. Biopsy is usually necessary to differentiate sparganosis from other possible diseases.