Angiostrongyliasis Cantonensis

Essentials of Diagnosis

• Eosinophilic meningoencephalitis

• Transient cranial neuropathies

General Considerations

• Nematodes of rats of the genus Angiostrongylus cause two distinct syndromes in humans

  • Angiostrongylus cantonensis, the rat lungworm, causes eosinophilic meningoencephalitis

  • Angiostrongylus costaricensis causes gastrointestinal inflammation

• In both diseases, human infection follows ingestion of larvae within slugs or snails (and also crabs, prawns, or centipedes for A cantonensis) or on material contaminated by these organisms

• Since the parasites are not in their natural hosts, they cannot complete their life cycles, but they can cause disease after migrating to the brain or gastrointestinal tract

• In A cantonensis infection, disease is caused primarily by worm larvae migrating through the CNS and an inflammatory response to dying worms

• A cantonensis can migrate from the brain to the pulmonary arteries

Demographics

• A cantonensis is seen primarily in southeast Asia and some Pacific islands; 82 cases have been reported in Hawaii between 2007 and 2017

Symptoms and Signs

• After an incubation period of 1 day to 2 weeks, presenting symptoms and signs include

  • Headache

  • Stiff neck

  • Nausea, vomiting

  • Cranial nerve abnormalities

  • Paresthesias

Differential Diagnosis

• Tuberculous, coccidioidal, or aseptic meningitis

• Neurocysticercosis

• Neurosyphilis

• Lymphoma

• Paragonimiasis

• Echinococcosis

• Gnathostomiasis

• Diagnosis strongly suggested by finding eosinophilic CSF pleocytosis (over 10% eosinophils) in patients with a history of travel to endemic area

• Peripheral eosinophilia may not be present

• Definitive diagnosis is made by recovery of A cantonensis larvae from the CSF and the eyes, although this is uncommon

• No specific treatment is available

• Antihelminthic therapy may be harmful for A cantonensis infection, since responses to dying worms may worsen with therapy

• If antihelminthic treatment is to be used, albendazole is probably the best choice, and therapy should be early in the disease course (within 3 weeks of exposure)

• Corticosteroids have commonly been used, and these are probably appropriate if antihelminthics are provided

Complications

• Parasite deaths may exacerbate CNS inflammatory lesions

Prognosis

• Most cases resolve spontaneously after 2–8 weeks

• However, serious sequelae and death have been reported

Prevention

• Controlling rat population

• Cooking snails, prawns, fish, and crabs for 3–5 min or by freezing them (–15°C for 24 h)

• Examining vegetables for mollusks before eating

• Washing contaminated vegetables to eliminate larvae contained in mollusk mucus is not always successful

When to Admit

• All patients