Sparganum proliferum is a rare parasitic infection that can affect humans. Its larval stage can multiply extensively within human tissues. Unlike other sparganosis forms, this proliferation results in a more aggressive and challenging disease.
Characteristics of Sparganum Proliferum
Sparganum proliferum is the larval stage (plerocercoid) of an unidentified cestode, a type of tapeworm. It differs from other Spirometra species causing typical sparganosis due to its capacity for asexual reproduction within the human body. Unlike single spargana, Sparganum proliferum can branch and multiply, forming a network of worms resembling a “Medusa head” or “Wasabi root.”
The larvae are white, wrinkled, and ribbon-shaped, varying from a few millimeters to several centimeters. Their anterior end can invaginate and may show indications of sucking grooves, though a true scolex is absent. This absence helps differentiate it from other cestode larvae like Taenia solium. While Spirometra is global, human sparganosis cases, including Sparganum proliferum, are primarily reported in East Asia, with some cases in Southeast Asia, South America, and elsewhere.
Pathways of Human Infection
The complete life cycle of Sparganum proliferum remains largely unknown, making its precise human infection pathways speculative. Humans serve as accidental or paratenic hosts in the Spirometra life cycle, which includes Sparganum proliferum. The general Spirometra life cycle involves adult worms in dogs and cats shedding eggs into freshwater. These hatch into coracidia, ingested by copepods (freshwater crustaceans).
Copepods, containing procercoid larvae, are consumed by second intermediate hosts like fish, reptiles, or amphibians, where larvae develop into plerocercoids. Humans can become infected by ingesting water contaminated with infected copepods, or by consuming raw or undercooked meat from second intermediate hosts such as frogs, snakes, or wild boar. Another suspected, less common route involves applying raw poultices from infected animal flesh onto open wounds or mucous membranes, a practice sometimes seen in traditional medicine. Given its rarity, the exact prevalence of each transmission route is unclear. However, ingesting contaminated water or undercooked aquatic animals are considered the most likely methods.
Clinical Manifestations
The clinical presentation of Sparganum proliferum infection varies depending on where the proliferating larvae establish themselves. Early stages may be asymptomatic, but as spargana grow and migrate, they can cause a painful inflammatory reaction in surrounding tissues. Larvae commonly affect subcutaneous tissues and muscles, forming slowly growing, rubbery nodules that may migrate beneath the skin, sometimes called “creeping tumors.” These nodules can itch, swell, and become red, often with painful edema.
Beyond skin and muscles, larvae can invade various organs and tissues, leading to diverse and severe symptoms. If larvae migrate to the eyes, it can result in ocular sparganosis, characterized by eye pain, swelling, excessive tearing, and potential vision loss. Central nervous system involvement, particularly the brain, can lead to serious neurological symptoms like headaches, seizures, limb weakness, numbness, tingling, and other deficits depending on the affected brain region. Spargana can also reside in internal organs, including the urinary tract, lungs, and abdominal viscera, causing organ dysfunction. The uncontrolled proliferation and migration of Sparganum proliferum larvae often lead to a progressive and frequently fatal outcome, especially with extensive dissemination or central nervous system involvement.
Diagnosis and Treatment Approaches
Diagnosing Sparganum proliferum infection presents challenges due to its rarity and non-specific symptoms, which can mimic other conditions. A definitive diagnosis relies on identifying larvae through a tissue biopsy or surgical removal of the suspected lesion. Imaging techniques like MRI and CT scans can help locate lesions and identify characteristic patterns in the brain, suggesting sparganosis. However, confirmation generally requires histopathological examination of excised larvae to distinguish Sparganum proliferum from other parasitic infections or tumors.
There is no consistently effective specific antiparasitic drug treatment for Sparganum proliferum. While anthelmintics like praziquantel have been used for other Spirometra species, their efficacy against Sparganum proliferum is uncertain and generally poor. The primary treatment approach involves surgical excision of accessible larvae. However, due to the parasite’s ability to proliferate and migrate extensively, complete surgical removal is often not curative, especially with widespread tissue invasion or multiple organ involvement. This limited treatment efficacy contributes to the poor prognosis associated with Sparganum proliferum infection.