Meningitis is inflammation (swelling) of the protective lining around the brain and spinal cord. Some parasites cause it, or harm the brain and nervous system in other ways. Parasitic meningitis is less common than viral or bacterial meningitis, can be hard to diagnose, and its treatment focuses on calming the body's reaction to the parasite.
It is called EM, short for eosinophilic meningitis or eosinophilic meningoencephalitis.
Left: a Baylisascaris procyonis egg with a larva developing inside. Right: a larva hatching. Image from CDC's page.
The three main parasites
These parasites normally infect animals, not people. People catch them mainly by eating infected slugs, snails or contaminated food, or by accidentally swallowing raccoon feces.
| Parasite (disease) | Usual source | Where it is found | Prevention |
|---|---|---|---|
| Angiostrongylus cantonensis (neuroangiostrongyliasis) | Raw or undercooked snails or slugs; contaminated produce | Mostly Southeast Asia and the Pacific Islands, Hawaii included; also Africa, the Caribbean and the continental United States | Don't eat raw or undercooked slugs or snails |
| Baylisascaris procyonis (baylisascariasis; neural larva migrans) | Dirt and other surroundings contaminated with raccoon feces | Raccoons across the United States, mainly the Midwest, Northeast, Middle Atlantic and West Coast | Avoid raccoons and their feces |
| Gnathostoma spinigerum (neurognathostomiasis) | Raw or undercooked freshwater fish or eels, frogs, poultry, snakes | Most often Southeast Asia, particularly Thailand, and Japan | Don't eat raw or undercooked fish or poultry, especially in Southeast Asia and Japan |
Risk depends on the parasite but can include age, where you live, and what you eat. People in raccoon areas who handle raccoon feces are at higher risk of B. procyonis, and so are young children, who are more likely to put dirty fingers, soil or objects in their mouths. People generally do not pass parasitic meningitis, or the parasites behind it, to one another.
Symptoms and complications
People with parasitic EM who have symptoms can have the usual signs of meningitis, sometimes with an eye infection as well. With A. cantonensis, tingling or painful sensations in the skin are common.
The complications can be severe:
- loss of coordination and muscle control
- weakness or paralysis
- coma
- permanent disability
- death
Anyone with symptoms of meningitis should see a health care provider right away to learn whether it is meningitis, what is causing it and how to treat it.
Diagnosis and treatment
Alongside standard laboratory tests for meningitis, providers look for signs of a parasite — which are often hard to find. Travel or exposure history, a clinical examination and other tests such as brain scans can help.
- Steroids and similar medicines are often needed to reduce the body's reaction to the parasite.
- Antiparasitic medicines are not needed for every patient.
- Pain medicine can help with headaches.
Sources
Rewritten from the Centers for Disease Control and Prevention page "About Parasitic Meningitis" (public domain), in hubnx's own words.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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