Scary Diseases Part I: PAM

Students enrolled in Medicine classes can get very weird after a couple of semesters. They become overly interested in strategic parts of the human anatomy and tend to develop a number of seemingly uncanny habits, such as taking a whole five minutes to wash their hands.

I can relate. When our microbiology lecturer started talking about Naegleria fowleri (right¹), a protist that lives in warm freshwater, I made up my mind to never swim ever again.

Naegleria fowleri basically has the potential to kill you in a mere two weeks without you being able to do anything about it! The microbe, if in its trophozite or flagellated form, has the ability to get in the body through the nose, and from there penetrate its way into the brain. There, it appears they suck out the cytoplasm of brain cells and kill them; indeed quite literally they eat your brain! ²(Below, left.)

This disease is known as Primary Amoebic Meningoencephalitis (PAM) and manifests with symptoms similar to bacterial meningitis - which is usually treatable - such as headache, fever, vomiting and stiff neck. However, other symptoms like confusion, hallucinations and lack of attention to surroundings may soon appear, and are always followed by death.

There is no proper treatment for PAM, so even if the Naegleria fowleri is detected in the cerebrospinal fluid of a patient, nothing much can be done.

But maybe we shouldn't freak out. PAM is actually a very rare disease; statistics show that there were only 121 reported cases between 1937 and 2007 in the United States, about 3/year. So you have to be somewhat unlucky to catch this "bug." Compare those odds to those of drowning, which caused 36,000 deaths between 1996 to 2005 in the United States³.

All of it further strengthens my determination to not swim ever again!

-Khalil A. Cassimally

Images

Right image caption: The ameoba Naegleria fowleri, visualized with a fluorescent antibody stain³.

Left Image caption: Rat brain cell in absence or presence of Naegleria fowleri. A: Unaffected cell, B: N. fowleri in contact with brain cell after six hours of inoculation, C: Affected cell after 18 hours of inoculation, D: Remnants of brain cell 24 hours after inoculation².

Left image source: Marciano-Cabral, F. and John, D.T. (1983) Infection and Immunity 40(3) 1214-1217.

Endnotes

1. CDC Public Health Image Library, courtesy of Dr. Govinda S. Visvesvara.  

2. Marciano-Cabral, F. and John, D.T. "Cytopathogenicity of Naegleria fowleri for Rat Neuroblastoma Cell Cultures: Scanning Electron Microscopy Study" (1983) Infection and Immunity 40(3) 1214-1217.(reprint)

3. CDC fact sheet on "Naegleria Infection", Centers for Disease Control and Prevention. May 02, 2008.

References

Tolan, Robert. "Amebic Meningoencephalitis" emedicine, Medscape. January 21, 2009.

 "Naegleria fowleri and Primary Amebic Meningoencephalitis (PAM)" Davidson College.

 "Primary Amebic Meningoencephalitis --- Arizona, Florida, and Texas, 2007" Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention. May 30, 2008.