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Eosinophilic meningitis

Peter F Weller, MD, MACP
Section Editor
Edward T Ryan, MD, DTMH
Deputy Editor
Elinor L Baron, MD, DTMH


Eosinophilic meningitis is defined as the presence of more than 10 eosinophils/mm3 in the cerebrospinal fluid (CSF) and/or eosinophils accounting for more than 10 percent of CSF leukocytes [1]. Reliable detection of eosinophils in the CSF requires examination of centrifuged cell preparations stained with Wright's, Giemsa, or other appropriate stains. Eosinophils are found in the CSF in a limited number of diseases, including certain parasitic diseases and coccidioidal meningitis (table 1) [2-4]. The etiologies of eosinophilic meningitis will be reviewed here, with emphasis on the parasitic causes of this condition.

Some of the infectious agents that cause eosinophilic meningitis are parasites that are endemic outside of North America and Europe but have a global distribution due to travel. In addition, cases of eosinophilic meningitis due to these parasites may occur among travelers to both well-known and less known endemic regions [5-11].


There are three important parasitic infections associated with eosinophilic meningitis: Angiostrongylus cantonensis, Baylisascaris procyonis, and Gnathostoma spinigerum. These are parasites for which humans are incidental hosts. Localization to nervous tissue is a typical manifestation of A. cantonensis and B. procyonis infection for both natural and incidental hosts. G. spinigerum can cause meningeal or extrameningeal infection. In general, human infection due to these organisms is self-limited because larvae do not replicate or mature to adult worms. Eosinophilic meningitis occurs as a result of larval migration within the nervous system; peripheral eosinophilia is also observed.

Angiostrongylus cantonensis — A. cantonensis is the most common parasitic cause of eosinophilic meningitis. A. cantonensis larvae are neurotropic [12].

Epidemiology — Eosinophilic meningitis due to A. cantonensis occurs principally in Southeast Asia, particularly Thailand and Malaysia but also Southern Vietnam, as well as throughout the Pacific basin, including Indonesia, the Philippines, Taiwan, China, Japan, Papua New Guinea, Hawaii, and several smaller Pacific islands. Due in part to ship-borne dissemination of infected rats, the parasite has also been found outside of this broad area in regions of Africa, Australia, Cuba, Puerto Rico, and Jamaica and has spread from New Orleans into other areas of Louisiana [13-20].

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Literature review current through: Nov 2017. | This topic last updated: Sep 29, 2017.
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