Back in September 2007, I discussed the case of a 14-year old boy who contracted a "brain-eating amoeba" while swimming in Lake Havasu, Arizona. He died shortly thereafter, before medics could properly diagnose it as an infestation of naegleria fowleri. However, one could at least avoid it by not swimming in warm, stagnant water.
Unfortunately, naegleria fowleri has a land-based cousin, balamuthia mandrillaris, which is not so easily avoided, and a Murrieta, California fire captain has contracted it. He currently is on life-support in a critical care unit in San Diego. Captain Matt Moore, a 17-year veteran of the Murrieta Fire Department who is married with three teenage children, fell ill in November, he has been in and out of four hospitals, all the while growing sicker from a mysterious illness that doctors initially could not identify. Now they know that the illness is caused by a rare and usually fatal parasitic meningoencephalitis caused by a brain-eating amoeba found in soil. Full story published February 21st, 2008 in the Riverside (CA) Press-Enteprise.
About 150 cases of this disease -- all but a handful fatal - have been reported worldwide since scientists discovered in the early 1990s that the amoeba balamuthia mandrillaris can infect humans. Scientists had considered the amoeba harmless to mammals until it was found in 1986 in a mandrill -- an animal similar to a baboon -- that had died at the San Diego Wild Animal Park.
Dr. Fred Schuster, a researcher with the state Department of Public Health in Richmond, said there likely are many more undiagnosed human cases of balamuthia mandrillaris infection. Doctors often do not recognize the symptoms. And when a doctor is familiar with the disease, the amoeba is difficult to detect. In Matt Moore's case, it took a brain biopsy to pinpoint the parasite. Frequently, the infection is not discovered until the person has died, if then.
It appears that the amoeba infects humans by entering through a wound or by being inhaled after it has become airborne. Among those infected, Schuster said, "the common denominator is some contact with soil." In one case, researchers discovered the amoeba in soil in a flowerpot in an infected child's home. Others reported falling ill after gardening and digging in a compost pile. One man appears to have contracted the infection through a wound from a rosebush thorn.
But it is difficult to explain, Schuster said, the fact that "millions of people are in contact with soil, and very, very few develop this infection." Researchers suspect that many people are exposed, but infection develops, by and large, in those with some immune deficiency. Perhaps, Schuster said, that deficiency might be very subtle, almost undetectable.
A disproportionate number of the infections have been found in Latinos, but it is unknown whether genetics, environment or some other factors are to blame. Infections also appear more common in warmer climates such as Southern California. [Ed. Note: The disparity may be attributable to the fact that Latinos, probably because of their predominant occupations, probably come in contact with soil more frequently than other races in Southern California. It could even be resultant of the upsurge in immigration.]
It stands to reason, Schuster said, that firefighters might have a higher chance of exposure being around so many airborne particles on the job. "But it's just a wild guess," he said.
Unlike naegleria fowleri, a parasitic amoeba known to infect humans that is found in lakes and other warm fresh water, balamuthia mandrillaris may be nearly impossible to avoid, Schuster said. People can avoid swimming in naegleria fowleri-friendly water, he said, but it is hard to steer clear of dirt and windblown dust.
As a public health threat, Schuster said, "it's nothing to get panicked about because your chances of acquiring this disease are infinitesimal." But because of the high mortality rate among those unlucky enough to contract the disease, not to mention the fact that it often infects children, "it is a little frightening," he said.
In the critical-care unit at the UC San Diego Medical Center in Hillcrest, Moore is receiving an experimental "cocktail" of drugs that were given to some of the survivors of balamuthia mandrillaris infections, his wife said. But Moore already had taken a sudden turn for the worse before he was diagnosed.
Moore is in a coma. In his hospital bed this week, having lost about 40 pounds and being attached to a respirator and a riot of lines and monitors, he is almost unrecognizable as the smiling firefighter, posing with his buddies at the station, in a photograph taped to the wall along with hand-drawn get-well wishes and a Valentine from his wife. The last time he reportedly spoke was on January 18th.
Apparently, so little is known about this parasite that there is no separate entry for it in the Index of CDC Fact Sheets, which has an entry for naegleria. The Wikipedia entry on balamuthia mandrillaris tells us that there may be an external symptom which can alert docs to its existence before it gets too far into the brain. The external symptom is a skin lesion that may be slow to heal or to respond to dermatological treatment, and it may form far enough in advance that, if successfully diagnosed, could result in treatment before the amoeba actually reaches the brain. Other symptoms could include focal paralysis, seizures, and brainstem symptoms such as facial paralysis, difficulty swallowing, and double vision. I did find this CDC paper on balamuthia mandrillas which discusses its emergence among the Latino population.