What are the other Names for this Condition? (Also known as/Synonyms)

• Amebic Encephalitis
• Naegleria Meningoencephalitis
• PAM (Primary Amebic Meningoencephalitis)

What is Primary Amebic Meningoencephalitis? (Definition/Background Information)

• Primary Amebic Meningoencephalitis (PAM) is a rare but serious brain and spinal cord infection caused by the Naegleria fowleri amoeba. It is usually fatal and has a rapid onset of symptoms
• Primary Amebic Meningoencephalitis is more common in young children and is transmitted through contact with contaminated water or soil, typically when water enters the nose
• The risk factors for Primary Amebic Meningoencephalitis include living in or visiting areas where the disease is prevalent, engaging in water-related activities in contaminated water, and having a compromised immune system
• The signs and symptoms of Primary Amebic Meningoencephalitis may vary from one individual to another and may include fever, headache, nausea and vomiting, stiff neck, seizures, and coma
• A diagnosis of Primary Amebic Meningoencephalitis is made through a combination of a physical examination and laboratory testing. A sample of spinal fluid will be taken and tested for the presence of the Naegleria fowleri amoeba
• Treatment is usually limited to supportive care, such as medications to alleviate symptoms and mechanical ventilation to assist with breathing. Antibiotics may be used in some cases, but they are generally ineffective against Primary Amebic Meningoencephalitis
• To prevent this deadly infection, avoiding activities that may result in water entering the nose, such as diving or water skiing in contaminated water is important. It is also essential to use proper water disinfection techniques, such as boiling or using chemicals when using water from non-chlorinated sources
• The prognosis for Primary Amebic Meningoencephalitis is generally unfavorable, and the death rates are very high. Early diagnosis and management of PAM may improve the chances of survival, but the infection can progress quickly and is usually difficult to treat

Who gets Primary Amebic Meningoencephalitis? (Age and Sex Distribution)

• Primary Amebic Meningoencephalitis can affect people of all ages, but it is more common in young children
• Both males and females are affected
• The infection may be seen worldwide, and no racial or ethnic group preference is noted

What are the Risk Factors for Primary Amebic Meningoencephalitis? (Predisposing Factors)

The risk factors for Primary Amebic Meningoencephalitis include:

• Living in or visiting areas where the disease is prevalent
• Engaging in water-related activities that increase the risk of exposure to contaminated water
• Having a weakened immune system

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Primary Amebic Meningoencephalitis? (Etiology)

Primary Amebic Meningoencephalitis is caused by the Naegleria fowleri amoeba.

• It is transmitted through contact with contaminated water or soil, typically when water enters the nose
• It is thought that the Naeglaria organisms enter the brain through the olfactory (smell) complex at the top of the pharynx area. Amebas can move toward their preferred environments by extending their membrane

The waterbodies most likely to harbor the Naeglaria fowleri ameba are usually stagnant, shallow, warm, and with a foul-smelling muck bottom. Water experts would describe this environment as ‘anaerobic’, reflecting its low oxygen content. Cases have also come from geothermal hot springs, untreated hot (geothermal) drinking water, splash pads, swimming pools that are poorly maintained or minimally chlorinated, water heaters, or soil. It is important to note that Naeglaria do not grow in salt water. 

What are the Signs and Symptoms of Primary Amebic Meningoencephalitis?

The signs and symptoms of Primary Amebic Meningoencephalitis can vary but may include:

• Fever
• Headache
• Nausea and vomiting
• Stiff neck
• Seizures
• Coma

The signs and symptoms typically begin within 1 to 7 days after exposure to the amoeba.

How is Primary Amebic Meningoencephalitis Diagnosed?

• Primary Amebic Meningoencephalitis is diagnosed through physical examinations and laboratory testing
• A sample of spinal fluid will be taken and tested for the presence of the Naegleria fowleri amoeba

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Primary Amebic Meningoencephalitis?

Primary Amebic Meningoencephalitis is usually fatal, with a very high death rate.

How is Primary Amebic Meningoencephalitis Treated?

The treatment for Primary Amebic Meningoencephalitis is usually limited to supportive care, such as 

• Medications to alleviate symptoms
• Mechanical ventilation to assist with breathing

Antibiotics may be used in some cases, but they are generally ineffective against the amoeba.

How can Primary Amebic Meningoencephalitis be Prevented?

To prevent Primary Amebic Meningoencephalitis, the following may be considered:

• Avoid activities in contaminated water that may result in water entering the nose, such as diving or water skiing
• Use proper water disinfection techniques, such as boiling or using chemicals, when using water from non-chlorinated sources

What is the Prognosis of Primary Amebic Meningoencephalitis? (Outcomes/Resolutions)

• The prognosis for Primary Amebic Meningoencephalitis is generally poor, with a death rate of over 95%
• Early diagnosis and treatment may improve the chances of survival, but the infection can progress quickly and be challenging to treat

From 1962-2021, 154 cases were reported to the US CDC, of which only four survived.

Additional and Relevant Useful Information for Primary Amebic Meningoencephalitis:

The following DoveMed website link is a useful resource for additional information:

https://www.dovemed.com/common-procedures/radiology-procedures/lumbar-puncture