
FAQs Data Reporting Investigation Resources
Disease Condition
Primary
Amebic Meningoencephalitis and Other Amebic Meningitis/Encephalitis
Organism
Primary
Amebic Meningoencephalitis (PAM) is caused by an ameba called Naegleria fowleri. 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.
Other central nervous system (CNS) infections may be caused by other amebae
such as Sappinia species (including S. diploidea and S. pedata).
Transmission
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:
- Naegleria fowleri infects people when water
containing the ameba enters the body through the nose. This typically occurs
when people go swimming or diving in warm freshwater places, like lakes and
rivers. In very rare instances, Naegleria
infections may also occur when contaminated water from other sources (such as
inadequately chlorinated swimming pool water or contaminated tap water) enters
the nose, such as when people submerge their heads or cleanse their noses
during religious practices, and when people irrigate their sinuses (nose) using
contaminated tap water. The Naegleria
fowleri ameba then travels up the nose to the brain where it destroys the
brain tissue. Naegleria fowleri has
not been shown to spread via water vapor or aerosol droplets (such as shower
mist or vapor from a humidifier), and you cannot be infected with Naegleria fowleri by drinking
contaminated water.
While infections with Naegleria
fowleri are rare, they occur mainly during the summer months of July,
August, and September. Infections are more likely to occur in southern-tier
states. Infections usually occur when it is hot for prolonged periods of time,
which results in higher water temperatures and lower water levels.
- Balamuthia is thought to enter 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.
- Acanthamoeba can enter the skin through a
cut or wound, or through the nostrils. Once inside the body, the amebae travel
through the bloodstream to other parts of the body, especially the lungs,
brain, and spinal cord.
- Sappinia 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.
Symptoms
The
symptoms of amebic meningitis/encephalitis vary depending on the infecting
ameba:
- Primary
Amebic Meningoencephalitis (PAM)/Naegleria
fowleri: In its early stages, symptoms of PAM may be similar to symptoms of
bacterial meningitis. Initial symptoms of PAM start about 5 days (range 1 to 7
days) after infection. The initial symptoms may include headache, fever,
nausea, or vomiting. Later symptoms can include stiff neck, confusion, lack of
attention to people and surroundings, loss of balance, seizures, and hallucinations.
After the start of symptoms, the disease progresses rapidly and usually causes
death within about 5 days (range: 1 to 12 days).
- Granulomatous
Amebic Encephalitis (GAE)/Balamuthia
mandrillaris: The infection can begin with a skin wound on the face, chest,
torso, arms, or legs. If the infection involves the brain, the disease it
causes is called GAE.
- Diagnosis of Balamuthia GAE can be difficult, but
some early symptoms might include:
- Headaches
- Stiff neck or head and neck pain
with neck movement
- Sensitivity to light
- Nausea
- Vomiting
- Lethargy (tiredness)
- Low-grade fever
- Other signs of Balamuthia GAE might include:
- Behavioral changes
- Seizures
- Weight loss
- Partial paralysis
- Difficulty speaking in full sentences
- Difficulty walking
The disease might appear mild at first but can become more severe over
weeks to several months. Often the disease is fatal, with a death rate of more
than 95%. Early diagnosis and treatment may increase the chances for survival.
- Granulomatous
Amebic Encephalitis (GAE)/Acanthamoeba
species: This is a serious, most often deadly, infection of the brain and
spinal cord. Once infected, a person may suffer with headaches, stiff neck,
nausea and vomiting, tiredness, confusion, lack of attention to people and
surroundings, loss of balance and bodily control, seizures, and hallucinations.
Symptoms progress over several weeks and death usually occurs.
- Amebic
encephalitis/Sappinia species: There
is only one known case of Sappinia
encephalitis in a human. Symptoms of Sappinia
infection may include:
- Headache
- Sensitivity to light
- Nausea or upset stomach
- Vomiting
- Blurry vision
- Loss of consciousness
A scan of the one known infected patient’s brain also revealed a
2-centimeter tumor-like mass on the back left section of his brain.
Some groups
have a higher risk of infection or disease:
- Primary
Amebic Meningoencephalitis: PAM disproportionately affects males and children.
The reason for this distribution pattern is unclear but may reflect the types
of water activities (such as diving or watersports) that might be more common
among young boys. The extremely low occurrence of PAM makes epidemiologic study
difficult.
- Granulomatous
Amebic Encephalitis: Balamuthia
infection can occur in anyone. GAE or disseminated infection caused by Acanthamoeba occurs more frequently in
people with compromised immune systems or those who are chronically ill.
- Amebic
encephalitis caused by Sappinia
species: 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.
Prevention
Primary
Amebic Meningoencephalitis:
Although
infections are severe, the risk of Naegleria
fowleri infection is very low. There have been 30 reported infections in
the U.S. during the 10 years from 2000-2009, despite millions of recreational
water exposures each year. By comparison, during the ten years from 1996 to
2005, there were over 36,000 drowning deaths in the U.S. It is likely that a
low risk of Naegleria fowleri
infection will always exist with recreational use of warm freshwater lakes,
rivers, and hot springs. The low number of infections makes it difficult to
know why some people have been infected compared to the millions of other
people using the same or similar waters across the U.S. The only way to prevent
Naegleria fowleri infection is to
refrain from water-related activities. If you do plan to take part in
water-related activities, here are some measures that might reduce risk:
- Avoid
water-related activities in bodies of warm freshwater during periods of high
water temperature and low water levels.
- Hold the
nose shut or use nose clips when taking part in water-related activities in
bodies of warm freshwater such as lakes, rivers, or hot springs.
- Avoid
digging in or stirring up the sediment while taking part in water-related
activities in shallow, warm, freshwater areas.
- Use only
sterile, distilled, or lukewarm previously boiled water for nasal irrigation or
sinus flushes (e.g., Neti Pot usage, ritual nasal ablution, etc.).
Granulomatous
Amebic Encephalitis:
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 1972-2015, 11 other amebic meningitis/encephalitis
cases were reported to DSHS, eight caused by Balamuthia mandrillaris, two caused by Acanthamoeba species, and one 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.