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Angiostrongyliasis

By Richard D. Pearson, MD, Emeritus Professor of Medicine, University of Virginia School of Medicine

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Angiostrongyliasis is infection with larvae of worms of the genus Angiostrongylus; intestinal symptoms or eosinophilic meningitis occurs depending on the infecting species.

Angiostrongylus are parasites of rats (rat lung worms). Excreted larvae are taken up by intermediate hosts (snails and slugs) and paratenic or transport hosts (hosts that are not required for the parasite's development but that can transmit infection to humans). Human infection is acquired by ingestion of raw or undercooked snails or slugs or transport hosts (certain crabs and freshwater shrimp); it is unclear whether larval contamination of vegetables (eg, in slime from snails or slugs that crawl on the food) can cause infection.

A. cantonensis infection occurs predominantly in Southeast Asia and the Pacific Basin, although infection has been reported elsewhere, including the Caribbean, Hawaii, and Louisiana. The larvae migrate from the GI tract to the meninges, where they cause eosinophilic meningitis, with fever, headache, and meningismus. Occasionally, ocular invasion occurs.

A. costaricensis infection occurs in the Americas, predominantly in Latin America and the Caribbean. Adult worms reside in arterioles of the ileocecal area, and eggs can be released into the intestinal tissues, resulting in local inflammation with abdominal pain, vomiting, and fever; this infection can mimic appendicitis. Also, abdominal angiostrongyliasis is often accompanied by eosinophilia, and a painful right lower quadrant mass may develop.

Diagnosis

  • If meningitis signs are present, CSF analysis (for A. cantonensis)

  • Sometimes identification of eggs and larvae during abdominal surgery (for A. costaricensis)

Angiostrongyliasis is suspected based on a history of ingesting potentially contaminated material.

Patients with meningeal findings require lumbar puncture; CSF shows eosinophilia, but A. cantonensis parasites are rarely visible.

Diagnosis of GI infection due to A. costaricensis is difficult because larvae and eggs are not present in stool; however, if surgery is done (eg, for suspected appendicitis), eggs and larvae can be identified in tissues removed during surgery.

Immunoassays are not widely available.

Treatment

  • For meningitis, analgesics, corticosteroids, and removal of CSF

A. cantonensis meningitis is treated with analgesics, corticosteroids, and removal of CSF at frequent intervals to reduce CNS pressure. Anthelmintic therapy may increase the inflammatory response because it results in the release of parasite antigens. Most patients have a self-limited course and recover completely.

There is no specific treatment for A. costaricensis infection; most infections resolve spontaneously. Anthelmintics do not appear to be effective and may lead to additional migration of worms and worsening symptoms.

Prevention

People who live in or travel to areas with A. cantonensis should avoid eating raw or undercooked snails, slugs, freshwater shrimp, land crabs, frogs, and lizards, as well as potentially contaminated vegetables and vegetable juices.

People who live in or travel to areas with A. costaricensis should avoid eating raw or undercooked slugs and potentially contaminated vegetables or juices.

Key Points

  • Humans acquire Angiostrongylus when they consume raw or undercooked snails or slugs or the organisms' transport hosts (land crabs and freshwater shrimp).

  • A. cantonensis larvae migrate from the GI tract to the meninges, where they cause eosinophilic meningitis; A. costaricensis eggs can be released into the intestinal tissues, causing abdominal pain, vomiting, and fever.

  • Treat A. cantonensis meningitis with analgesics, corticosteroids, and, if intracranial pressure is elevated, removal of CSF at frequent intervals.

  • Treating A. costaricensis infection with anthelmintics does not appear to be effective and may lead to additional migration of worms and worsening symptoms; most of these infections resolve spontaneously.

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