Primary Amebic Meningoencephalitis (PAM)
Naegleria fowleri- the only species of Naegleria known to infect humans.
Naegleria fowleri (an ameba) is found in warm fresh water such as rivers, lakes and ponds. Exposure occurs when people go swimming or diving in warm freshwater places, like lakes and rivers. The organism has also been found in tap water and can be introduced to the brain when tap water is used for nasal irrigation or sinus flushes. However, people do not become infected from drinking contaminated water.
In very rare instances, Naegleria infections may also occur when contaminated water from other sources (such as inadequately chlorinated swimming pool water or heated and contaminated tap water) enters the nose. This may occur when such water is used for nasal irrigation, sinus flushes, or cleansing rituals.
Human exposure to Naegleria fowleri occurs when water containing amebae enters the nose. Amebae are thought to be introduced to the brain by forced entry of water up the nose during fresh-water recreational activities. Transmission occurs when the free-living form of the ameba, a trophozoite, penetrates the nasal tissue and migrates to the brain via the olfactory nerves causing primary amebic meningoencephalitis.
Infection can occur in young healthy (immune-competent) individuals.
- Initial signs and symptoms may consist of: 1) sudden onset of headache, 2) fever, 3) nausea and vomiting, 4) stiff neck, and 5) presence of meningeal signs. Other focal neurological symptoms might occur at onset or later on as the disease progresses such as, abnormalities in taste or smell, nasal obstruction and nasal discharge.
- As the disease progresses new symptoms might develop: photophobia, mental-state abnormalities, lethargy, dizziness, loss of balance, other visual disturbances, hallucinations, delirium, seizures, and coma. After the onset of symptoms, the disease progresses rapidly and usually results in death within 3 to 7 days.
Prevention & Treatment Prevention
Be educated and make informed decisions:
- 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 infections 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.
- If you use a Neti-Pot or syringe for nasal irrigation or sinus flushes be sure to use only sterile, distilled, or lukewarm previously boiled water.
- Anyone experiencing symptoms shoud be evaluated by a physician.
- Several drugs are effective against Naegleria fowleri in the laboratory. For up to date information on treatment, refer to the CDC website:
Naegleria fowleri: http://www.cdc.gov/parasites/naegleria/treatment.html
If you are a physician and healthcare professional considering amebic meningoencephalitis or encephalitis:
- CONTACT the Emerging and Acute Infectious Disease Branch at the Texas Department of State Health Services at (512) 776-7676
- ASK to speak with the amebic meningitis & encephalitis surveillance coordinator/epidemiologist.
Recent Texas Trends
- There are no known cases of PAM to have occurred in Texas during 2011 and 2012.
- From 1983 - 2012 there were 28 cases of PAM reported to the Texas Department of State Health Services - average incidence rate over the past 30 years is 0.93 cases per year (just under 1 case per year).
- Most cases occurred in young males 9-12 year of age with a history of recent exposure to freshwater lakes, ponds and rivers during the warm summer months.
- No Texas cases have been linked to nasal irrigation or sinus flushes.