Spirometra (sparganosis)

At a glance

Shape

Whitish, wrinkled, ribbon-like larva without suckers or hooks

Family

Diphyllobothriidae

Type

Pseudophyllidean cestode; humans host the second-stage larva (plerocercoid, sparganum)

Size

Sparganum a few millimetres wide and several centimetres long

Morphology

• The sparganum is flat, white and unsegmented, with a slightly thickened front end.
• It can live for many years in human tissue.
• S. proliferum branches and multiplies, producing many larvae.

Transmission

• Drinking untreated water containing infected copepods (water fleas).
• Eating raw or undercooked frog, snake or other second intermediate or paratenic host flesh.
• Applying raw frog or snake flesh as a poultice to wounds or eyes (a folk practice in parts of Asia).

Reservoir: Dogs, cats and wild carnivores (definitive hosts); Copepods (first intermediate host); Frogs, snakes, fish and other vertebrates (second intermediate or paratenic hosts)

Isolation precautions

What the care team adds to standard precautions.

• Standard

Life cycle

1. The adult lives in the intestine of a dog or cat; eggs leave in the faeces and reach water.
2. A coracidium hatches and is eaten by a copepod, where it becomes a procercoid.
3. A frog, snake or fish eats the copepod; the larva becomes a plerocercoid (sparganum) in its tissues.
4. A dog or cat eats the infected animal and the adult develops in its gut.
5. A person swallowing copepods or raw infected flesh carries the sparganum, which migrates but never matures.

Virulence factors

• The larva migrates through tissues, leaving tracts and inflammatory granulomas with eosinophils.
• In the brain or spinal cord it causes mass lesions that change position over time.
• Proliferative forms invade many tissues and can be fatal.

Diseases it causes

• Subcutaneous sparganosis: slow, sometimes migratory, painless swelling of the skin or muscle
• Ocular sparganosis: periorbital swelling, eyelid oedema, sometimes proptosis
• Cerebral or spinal sparganosis: seizures, headache, weakness and sensory changes

Clinical picture

• A subcutaneous lump that moves over weeks to months, often on the trunk, limbs or breast.
• Eye involvement causes swelling, pain and tearing.
• Brain involvement: seizures, hemiparesis, headache; inner ear involvement causes vertigo or deafness.
• Eosinophilia may be present but is often absent.

Diagnosis

• Recovery of the sparganum from tissue at surgery is diagnostic.
• MRI of the brain: clusters of ring-enhancing lesions, a tunnel-like track, lesions that move between scans.
• Serology (ELISA for Spirometra IgG in serum or CSF) where available.
• PCR on the larva identifies the species.

Treatment

Complete surgical removal of the live larva is the standard; the cestocide praziquantel has been used, especially in cerebral disease, but its benefit is uncertain.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

• Praziquantel

Prevention

• Drink boiled or filtered water in rural areas.
• Do not eat raw or undercooked frog, snake or wild animal meat.
• Avoid applying raw animal flesh to wounds or eyes.

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Connections

← Back to the group: Cestodes (tapeworms)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: CDC - DPDx - Sparganosis (CDC, 2017); Efficacy comparison between long-term high-dose praziquantel and surgical therapy for cerebral sparganosis: A multicenter retrospective cohort study (PLoS Neglected Tropical Diseases (PMC), 2018).

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Representative model, for educational purposes only.