L & R: Trophozoites of N. fowleri in brain tissue, stained with H&E. Center: Ameboflagellate trophozoite of N. fowleri. Credit: DPDx
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While it is exceedingly rare, each summer we hear of one or two fatal cases of PAM (Primary Amoebic Meningoencephalitis) here in the United States caused by an infection usually acquired while swimming in warm lakes and streams.
Tragically, an 8-year old boy from South Carolina has become the latest victim (see Amoeba kills Sumter youth –The State).
Blake Driggers reportedly fell ill a week after swimming in Lake Marion and was rushed to the hospital by his family.
Roughly a week later he died. With no effective treatment, survival with this infection is very rare.
Last year, in Sometimes It’s Zebras I wrote about this usually fatal form of meningitis caused by the Naegleria fowleri parasite.
N. flowleri is an amoeba, which can often be found in the silt at the bottom of warm water lakes and streams. If absorbed through the nostrils - it can make a beeline towards the brain.
Although usually only a danger to swimmers, last year we saw a new wrinkle when 2 people in Louisiana became infected through the introduction of tap water into their sinuses using a neti pot.
Photo Credit – Wikipedia Commons
These incidents caused the Louisiana Health Department to recommend that people `use distilled, sterile or previously boiled water to make up the irrigation solution’ (see Neti Pots & Naegleria Fowleri).
While it made a lot of headlines, this was not the first time that nasal irrigation has been linked to PAM. Several years ago N. fowleri contaminated tap water in Karachi, Pakistan may have caused 13 cases over 18 months.
According to the CDC’s FAQ on Naegleria, we average 2 to 4 infections each year in the United States with this parasite. They list the common sources of the amoeba as:
Where is Naegleria fowleri found?
Naegleria fowleri is found around the world. In the United States, the majority of infections have been caused by Naegleria fowleri from freshwater located in southern-tier states (2). The ameba can be found in:
- Bodies of warm freshwater, such as lakes and rivers
- Geothermal (naturally hot) water, such as hot springs
- Warm water discharge from industrial plants
- Geothermal (naturally hot) drinking water sources
- Soil
- Swimming pools that are poorly maintained, minimally-chlorinated, and/or un-chlorinated
- Water heaters with temperatures less than 47°C (3, 4)
Naegleria fowleri is not found in salt water, like the ocean.
Since millions of people swim in waters where this amoeba naturally occur (or are otherwise exposed) and only a small handful of infections result, the odds of acquiring this infection are extraordinarily low.
But the Florida Department of Health has some common sense safety advice on how to avoid this parasite.
Photo Credit – Florida DOH
For more information on the Naegleria parasite, you can visit the CDC’s Naegleria webpage.
UPDATE:
While I was writing this blog, Ronan Kelly and Alert over at FluTrackers were posting on a recent spate of deaths due to Naegleria – once again in Karachi, Pakistan.
The number of deaths being reported varies depending on the source, but the media is reporting between 3 and 8 fatalities over the past couple of weeks.
You can follow the media reports in this thread.
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