Amebic Meningitis / Encephalitis
Data FAQs Immunization Investigation Reporting Resources
Amebic CNS infections (amebic meningitis/encephalitis) are caused by microscopic, free-living amebae (single-celled living organisms).
Granulomatous Amebic Encephalitis (GAE) is caused by Balamuthia mandrillaris or by Acanthamoeba species, including A. culbertsoni, A. polyphaga, A. castellanii, A. astronyxis, A. hatchetti, A. rhysodes, A. divionensis, A. lugdunensis, A. lenticulata, and A. haelyi.
Primary Amebic Meningoencephalitis (PAM) is caused by Naegleria fowleri. For more information about PAM, please visit the Primary Amebic Meningoencephalitis webpage.
Other central nervous system (CNS) infections may be caused by other amebae such as Sappinia species (including S. diploidea and S. pedata).
Amebic meningitis/encephalitis infections are not spread from person to person. The amebae that cause amebic meningitis/encephalitis enter the body through different routes, depending on the specific ameba:
- Enters the body when soil containing Balamuthia comes in contact with skin wounds and cuts, or when dust containing Balamuthia is breathed in or gets in the mouth. Once inside the body, the amebae can travel through the blood stream to the brain, where they cause GAE. There are also a few reports of dogs that might have become infected after swimming in ponds. Finally, there have been reports of Balamuthia transmission to organ transplant recipients from infected donors.
- There have been a few reports of Balamuthia transmission to organ transplant recipients from infected donors.
- Enters the skin through a cut or wound, or through the nostrils when breathed in.
- Once inside the body, the amebae travel through the bloodstream to other parts of the body, especially the lungs, brain, and spinal cord.
- May enter the body through the nose or via cuts and bruises on the body.
- In the only known case, the patient had signs of a sinus infection before developing symptoms of amebic encephalitis.
The symptoms of Granulomatous Amebic Encephalitis (GAE) vary depending on the infecting ameba:
Balamuthia mandrillaris infection is very rare and serious, with a death rate of more than 89%. The disease might appear mild at first, but can become more severe over weeks to several months. Early diagnosis and treatment may increase the chances for survival.
Disease begins with a skin wound and can then travel to the brain causing GAE. Diagnosis of Balamuthia GAE can be difficult, but some early symptoms might include:
- Stiff neck or head and neck pain with neck movement
- Sensitivity to light
- Lethargy (tiredness)
- Low-grade fever
Other signs of Balamuthia GAE might include:
- Behavioral changes
- Weight loss
- Partial paralysis
- Difficulty speaking in full sentences
- Difficulty walking
Acanthamoeba species: This is a serious, most often deadly, infection of the brain and spinal cord. Symptoms progress over several weeks and death usually occurs.
- Stiff neck
- Nausea and Vomiting
- Lack of attention
- Loss of balance and bodily control
Sappinia species: There is only one known case of Sappinia encephalitis in a human. A scan of the one known infected patient’s brain revealed a 2-centimeter tumor-like mass on the back left section of the brain. Symptoms of Sappinia infection may include:
- Sensitivity to light
- Nausea or upset stomach
- Blurry vision
- Loss of consciousness
Some groups have a higher risk of infection or disease:
- Balamuthia infection can occur in anyone.
- GAE caused by Acanthamoeba occurs more frequently in people with compromised immune systems or those who are chronically ill.
- Amebic encephalitis caused by Sappinia
can infect anyone. However, individuals with weakened immune systems and people who have contact with animal feces are at a higher risk for infection.
Currently, there are no known ways to prevent infection with Balamuthia or Acanthamoeba. Since persons with weakened immune systems are more susceptible to Acanthamoeba infection, they should follow the advice of their treating physician carefully.
Recent Texas Trends
Other Amebic Meningitis and Encephalitis including Granulomatous Amebic Encephalitis (GAE):
From 1972-2020, 19 other amebic meningitis/encephalitis cases were reported to DSHS, 11 caused by Balamuthia mandrillaris, 5 caused by Acanthamoeba species, and 1 by a Sappinia species. Texas’ 1998 Sappinia pedata encephalitis case is the only known case of amebic encephalitis caused by Sappinia, worldwide. In 2012, Texas confirmed a case of Acanthamoeba healyi, a species not previously reported to cause human amebic encephalitis.
Although GAE infections and other amebic meningitis and encephalitis cases have always been reportable to Texas health departments as exotic diseases, before 2012, PAM was the only amebic infection of the central nervous system that was listed on the Texas Notifiable Conditions list.