Angiostrongylus cantonensis , rat lungworm, a nematode parasite.
Various species of rats are the definitive hosts of the parasite, known as the rat lungworm. Parasites from rats only infect snails and slugs, which are the intermediate hosts. Infective larvae have also been found in paratenic (transport) hosts, such as freshwater shrimp, crabs, and frogs, which become infected by consuming infected snails and slugs. Transmission to humans occurs by ingesting infected intermediate or paratenic hosts or by consuming contaminated raw produce or vegetable juices.
Most described cases have occurred in Asia and the Pacific Basin (such as in parts of Thailand, Taiwan, mainland China, Australia, the Hawaiian Islands, and other Pacific Islands); however, cases have been reported in many areas of the world, including the Caribbean.
Incubation period is typically 1–3 weeks but ranges from 1 day to >6 weeks. A. cantonensis is considered the most common infectious cause of eosinophilic meningitis in humans. Common manifestations include headache, photophobia, stiff neck, abnormal skin sensations (such as tingling or painful feelings), nausea, vomiting, fatigue, and body aches. A low-grade fever may occur. Symptoms are usually self-limited but may persist for weeks or months. Severe cases can be associated with paralysis, blindness, or death.
Typically presumptive, on the basis of clinical and epidemiologic criteria in people with otherwise unexplained eosinophilic meningitis. PCR testing of cerebrospinal fluid is available at CDC (www.cdc.gov/dpdx; 404-718-4745; firstname.lastname@example.org). Immunodiagnostic tests have been developed (for example, in research settings) but are not approved or licensed for clinical use in the United States.
The larvae die spontaneously and supportive care usually suffices, including analgesics for pain and corticosteroids to limit inflammation. No antihelminthic drugs have been proven to be effective in treatment.
Food and water precautions, particularly:
- Avoid eating raw or undercooked snails, slugs, and other possible hosts.
- Eat raw produce, such as lettuce, only if it has been thoroughly washed or treated with bleach. Such measures might provide some protection but may not eliminate the risk.
- If a catchment tank is used as a source of water, ensure that it is covered to prevent intrusion by slugs and snails. Also keep drink containers covered.
- Wear gloves (and wash hands) if snails or slugs are handled.
CDC website: www.cdc.gov/parasites/angiostrongylus
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Anne Straily, Barbara L. Herwaldt