Parasitic Meningitis

Various parasites can cause meningitis or can affect the brain or nervous system in other ways. Overall, parasitic meningitis is much less common than viral and bacterial meningitis.

Some parasites can cause a rare form of meningitis called eosinophilic meningitis, eosinophilic meningoencephalitis, or EM, with increased levels of eosinophils (a type of white blood cell) in the fluid around the brain and spinal cord (the cerebrospinal fluid; CSF). EM also can be caused by other types of infections (not just by parasites) and can have noninfectious causes, such as medications.

The three main parasites that cause EM in some infected people are:

• Angiostrongylus cantonensis (neurologic angiostrongyliasis)
• Baylisascaris procyonis (baylisascariasis; neural larva migrans)
• Gnathostoma spinigerum (neurognathostomiasis)

How These Parasites Spread

These parasites normally infect animals not people, and they are not spread from one person to another. People get infected by ingesting something that has the infectious form or stage of the parasite. Please visit CDC’s websites for additional details about how these parasites are spread, besides the examples listed here:

• People can get infected with A. cantonensis in various ways, such as by ingesting raw or undercooked snails or slugs or by eating contaminated produce.
• People get infected with B. procyonis by accidentally ingesting infectious parasite eggs in raccoon feces or in something (such as dirt) contaminated with raccoon feces.
• People can get infected with G. spinigerum in various ways, such as by eating raw or undercooked freshwater fish or eels, frogs, poultry, or snakes.

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People at Risk

Some people may have increased risk for infection because of where they live or travel:

• People in many parts of the world have gotten infected with A. cantonensis—especially, but not only, in parts of Asia and the Pacific Islands, including in Hawaii.
• B. procyonis is found in raccoons in parts of the United States, especially in the mid-Atlantic, northeastern, and midwestern regions, as well as parts of California. People in these areas, particularly young children, who put dirt or animal waste in their mouth or who spend time around raccoons are at increased risk for Baylisascaris infection.
• The neurologic form of G. spinigerum infection is most common in Southeast Asia, particularly in Thailand.

Signs and Symptoms

If you think that you or your child might have meningitis, see a healthcare provider right away, for the appropriate testing and clinical management.

As with meningitis caused by other infections, people who develop symptomatic EM from these parasites can have headache, stiff neck, nausea, vomiting, photophobia (sensitivity to light), and/or altered mental status (confusion). Other symptoms/signs can be noted. For example, people with EM caused by A. cantonensis often have tingling or painful feelings in their skin and may have a low-grade fever.

All three of these parasites sometimes infect the eye(s). All three parasites, but most commonly Baylisascaris, can cause severe illness, such as with loss of coordination and muscle control, weakness/paralysis, coma, permanent disability, or death.

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Diagnosis

If meningitis is suspected, samples of blood and CSF (cerebrospinal fluid) are collected and sent for laboratory testing, to look for evidence of infection with these parasites and to rule out other causes. It often is hard to find these parasites in the CSF or in other parts of the body. But the person’s travel/exposure history may provide helpful clues, along with the findings of clinical examinations, laboratory testing, and scans (such as brain scans).

Treatment

The most common types of treatment for EM caused by these parasites are for the symptoms—such as pain medication for headache or medications to reduce the body’s reaction to the parasite—rather than for the infection itself. However, treatment for the infection might help some people.

Prevention

Please visit CDC’s websites listed in the Related Links section below to learn how to prevent infection with these and other parasites.

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