Sparganosis

What is sparganosis?

Sparganosis is a zoonosis, ie an infection passed on from animals such as snakes and frogs, and occasionally from eating pig or dog meat. It is caused by infection with the larval form of various species of Spirometra. These include:

• S. mansoni
• S. ranarum
• S. mansonoides
• S. erinacei
• Sparganum proliferum
  

The lifecycle of spargana tapeworm

The spargana tapeworm normally lives in the intestines of animals such as cats and dogs, and has two intermediate hosts.

• The first host is copepods, microscopic crustaceans that reside in freshwater.
• A wide range of amphibians, reptiles, birds, and mammals serve as second intermediate hosts (rarely including humans).
• Cats and dogs develop tapeworms when they eat the tapeworm larvae along with the smaller second intermediate hosts.
• Eggs are shed in the cat or dog faeces, and they hatch in water, when the cycle begins again.

Who gets sparganosis?

Sparganosis can occur in people who have:

• Eaten raw or undercooked seafood, or drunk water containing infected copepods
• Applied frog or snake meat contaminated with the larvae over their eyes (Chinese medicine) or onto an open wound

It occurs in residents of the following countries:

• Thailand
• China
• Japan
• Korea

Sparganosis is occasionally diagnosed in other countries among travellers. Reported cases describe a higher incidence in females compared to males.

What causes sparganosis?

Sparganosis may arise when individuals drink water contaminated with copepods infected with spargana larvae, or when they consume improperly cooked meat. It can also be caused by topical application of tissue derived from infected animals.

Spargana larvae penetrate the intestinal wall and migrate to other tissues.

Adult spirometra tapeworms are rarely seen in human beings.

What are the clinical features of sparganosis?

The clinical features of sparganosis are non-specific and it can be easily missed. Symptoms depend on which tissues the larvae have migrated to.

Cutaneous sparganosis occurs when sparganum larvae invade subcutaneous connective tissue and superficial muscles.

• Patients present with slowly growing, rubbery, subcutaneous nodules or tumours (0.5–5 cm).
• These are usually painless.
• Common sites are chest wall, lower extremities, cheek or scrotum.

Ocular sparganosis depends on the exact location of spargana within the eye. It may present as:

• Eyelid redness
• Swelling
• Subconjunctival or intraorbital mass
• Excessive lacrimation, itch or pain

Larvae in the cerebral hemisphere can cause:

• Fatigue
• Limb weakness
• Confusion
• Headache
• Seizure
• Memory loss
• Cerebral haemorrhage

If spinal canal is involved, sparganosis may cause:

• Recurrent lower back pain
• Bilateral numbness of lower limbs
• Urinary or bowel incontinence

Visceral spargana can invade breast, intestine, lung, heart or abdominal cavity.

Proliferative sparganosis can invade and spread from any organ.

• The larvae undergo continuous branching and budding to produce many progeny plerocoids.
• This has serious clinical effects and may be fatal.

How is sparganosis diagnosed?

Definitive diagnosis of sparganosis is based on the larvae being found in tissue samples.

• Eosinophilia supports the diagnosis.
• Antigen-specific IgG antibodies may be detected.

What is the treatment for sparganosis?

Spargana are removed surgically.

• All parts of the worm (including the scolex) must be removed or disease can reoccur.
• Surgery may be the only way to cure proliferative sparganosis.

If the worm is in lung or pericardium, surgery is not practical.

Other treatment options include:

• Chemotherapy with 40% ethanol procaine or α-chymotrypsin
• High dose of praziquentel for 2 days
• Albendazole or mebendazole for 6 months or longer

What is the outcome for sparganosis?

If not killed by treatment, spargana can live for 20 years in a human host.

Repeated serological tests are needed to prove clearance.