Author(s): Rebecca Chancey, Anne Straily

Infectious Agent

Angiostrongylus cantonensis, rat lungworm, a nematode parasite, causes angiostrongyliasis.

Transmission

Various species of rats are the definitive hosts of rat lungworm. Parasites from rats only infect slugs and snails, which are the intermediate hosts. Infective larvae also have been found in paratenic (transport) hosts (e.g., freshwater crabs, frogs, shrimp), which become infected by consuming infected slugs and snails. Transmission to humans occurs by ingesting infected intermediate or paratenic hosts contaminating raw produce or vegetable juices.

Epidemiology

A. cantonensis is considered the most common infectious cause of eosinophilic meningitis in humans. Most described cases have occurred in Asia and the Pacific Basin (e.g., parts of Australia, mainland China, Taiwan, Thailand, Hawaii, and other Pacific Islands); cases have been reported in many areas of the world, however, including Central and South America, the Caribbean, and parts of the continental United States. A review of the published literature in 2018 identified ≥77 cases of neuroangiostrongyliasis among travelers. All travelers are at risk, but adventure travelers might have more risky eating behaviors, predisposing them to exposure.

Clinical Presentation

Incubation period is typically 1–3 weeks but ranges from 1 day to >6 weeks. Common manifestations include body aches, headache, fatigue, photophobia, stiff neck, abnormal skin sensations (e.g., tingling or painful feelings), nausea, and vomiting. Low-grade fever is possible. Symptoms are usually self-limited but might persist for weeks or months. Severe cases can be associated with blindness, paralysis, or death.

Diagnosis

Diagnosis is typically presumptive, based on clinical and epidemiologic criteria in people with otherwise unexplained eosinophilic meningitis. Request PCR testing of cerebrospinal fluid through the Centers for Disease Control and Prevention’s DPDx laboratory (dpdx@cdc.gov), or the Parasitic Diseases Hotline for Healthcare Providers (404-718-4745; parasites@cdc.gov). Immunodiagnostic tests have been developed in research settings but are not approved or licensed for clinical use in the United States.

Treatment

A. cantonensis larvae die spontaneously, and supportive care usually suffices, including analgesics for pain and corticosteroids to limit inflammation. No anti-helminthic drugs have been effective in treatment. Although albendazole has been combined with corticosteroids in some cases, concern remains that anti-helminthic drugs will exacerbate symptoms due to a systemic response to dying worms. Lumbar puncture is required for etiological diagnosis of eosinophilic meningitis and can be repeated if clinically indicated to reduce intracranial pressure.

Prevention

Travelers can reduce their risk for infection by following safe food and water precautions. In particular, travelers should avoid eating raw or undercooked slugs, snails, and other possible hosts; and avoid eating raw produce (e.g., lettuce) unless it has been thoroughly washed with clean water, which might provide some protection but might not fully eliminate the risk. If a catchment tank is used as a source of water, travelers should ensure that the tank is covered to prevent intrusion by slugs and snails (see Sec. 2, Ch. 9, Water Disinfection) and keep their drink containers covered. In addition, travelers should wear gloves if they handle slugs or snails, and thoroughly wash hands afterwards.

CDC website: Angiostrongylus