Eosinophilic meningitis caused by Angiostrongylus cantonensis--a neglected disease with escalating importance.

The rat lungworm Angiostrongylus cantonensis, a food-borne zoonotic parasite, has been recognized as the primary pathogen associated with human eosinophilic meningitis or eosinophilic meningoencephalitis. This neurotropic nematode has a definitive rodent host and a molluscan intermediate host. The adult worms live in the pulmonary arteries of rats. Human is a non-permissive, accidental host. Transmission to humans is by eating of infected raw or undercooked snails, poorly cleaned contaminated vegetables or other infected paratenic hosts such as freshwater prawns, crabs, frogs or monitor lizards. Thousands of diagnosed cases of eosinophilic meningitis caused by A. cantonensis have been reported worldwide. Angiostrongyliasis is of increasing public health importance as globalization contributes to the geographical spread and more international travelers encounter the disease. The parasite is on the move. It has spread from its traditional endemic areas of Asia and the Pacific Basin to the American continent including the USA, Brazil and Caribbean islands. Recently, the incidence of human infections has increased rapidly. Most reports of the disease are from Thailand and Taiwan with increasing reports from mainland China. The rapid global spread of the parasite and the emerging occurrence of the infection pose challenges in clinical and laboratory diagnosis, and in epidemiology and basic biology. Enhanced understanding of the epidemiology of angiostrongyliasis, increased public awareness about the risks associated with eating raw or undercooked food, and enhanced food safety measures are needed. Therefore, current knowledge on various aspects of the parasite and the disease it causes, as well as recent epidemiological status together with significant progress in laboratory investigation of A. cantonensis infection, are overviewed to promote understanding and awareness of this emerging neglected disease.