Naegleria Fowleri meningoencephalitis or the "brain-eating" amoeba

Naegleria Fowleri is a single celled organism living free in hot springs, and in warm bodies of water and in soil, be they ponds, lakes, rivers, or streams.    In rare instances the organism has been known to invade the brains of victims, where the mortality rate from infection is > 95% or slightly less than one survivor in 20 infected.  In water where the organism lives, if a swimmer inadvertently gets water up into the nasal passages, the organism can attach itself to the olfactory nerve.

Hemorrhages and necrosis caused by N. fowleri encephalitis

  It migrates through the nerve endings through the cribiform plate to the olfactory bulb and from there to the rest of the brain.  The organism feeds and proliferates by consuming nerve and brain tissue as it goes along and leaving a necrotic path of destruction. 

The first symptoms is parosmia, which is an inability to identify odors properly, which leads to a total loss of the sense of smell.  From there is progresses to work on the cerebrum, bringing on frank encephalitis symptoms such as severe headache, nausea, and neck rigidity.  When the infection progresses to the brain stem, which controls breathing, death usually occurs.  

Arrows indicate N. fowleri in brain tissue.

By the time the organism is suspected or identified, it is generally too late.  Heroic measures involving high doses of drugs known to affect amoebic infections may be tried even though kidney function may in the process be destroyed. 

Such infections are fortunately quite rare.  The organism is very sensitive to chlorine as well.  There have been less than 300 confirmed cases of this disease as of 2008.   Two persons died in Louisiana while undergoing nasal irrigation in 2011.  A girl died after swimming in hot spring water in Bath, in the UK.in 1978. Nevertheless warnings are posted in areas where the organism is believed to be present.

The Geographic distribution of the disease, as befits a warm water organism is mostly in the southern states, as shown here. And the organism is not limited to just the US, but is present all over the world, though in warmer waters in the summer it is most likely to strike. 

In general, when swimming, don't do anything that might get water way up into the nose, especially in unchlorinated water.

Additional Information:

 http://www.wtsp.com/news/national/article/347184/81/A-deadly-parasite-moving-north

http://www.webmd.com/brain/brain-eating-amoeba

http://www.nbcnews.com/health/deadly-brain-amoeba-infects-first-us-drinking-water-system-8C11172643

http://www.thedailybeast.com/articles/2013/09/23/this-amoeba-eats-your-brain-naegleria-fowleri-rattles-new-orleans.html

Poliomyelitis

Poliomyelitis

It may not be scary to those of us who lived after the Sabin and Salk vaccines

Jonas Salk

largely eradicated the disease, at least in the developed world in 1955 (Salk's inactivated polio virus) and Sabin's oral polio vaccine which came out in 1957 but what was known as "infantile paralysis" it most certainly cast a shadow as one of those things that can and sometimes did cause morbidity and mortality.

  As a child growing up in a small town I knew myself two other children in my community who had been affected by polio, had effects which, tragically, are irreversible.  One of these was a classmate who was as a consequence had a deformed leg.  He wore a brace and limped.  The other was a girl a couple of years ahead of me in high school, who had lost the use of her legs, confined to a wheelchair and who had been curiously arrested in her growth to the size and appearance of the young child she had been when she had been stricken by the disease.    I also knew someone in college who similarly had been arrested in his growth

The most famous victim of the disease in this country  probably was Franklin D. Roosevelt, who was a hale and hearty man of  39, contracted the disease at Campobello Island in New Brunswick in 1921 and as a result was left with permanent paralysis from the waist down.

Others have retrospectively questioned whether Roosevelt had polio or Guillain-Barre syndrome, a rare complication of influenza that can have somewhat similar effects and is more likely to affect an adult. In spite of the paralysis he went on to become Governor of New York and later President, but then it was a simpler time when people read newspapers and listened to the radio.  One doubts whether in this video-glutted age such a feat would be possible.  There have been numerous other famous and semi-famous victims of polio, most of whom were stricken in childhood. Among these are Marion Davies, Johnny Weissmuller, Donald Sutherland, Alan Alda, Mia Farrow,  Francis Ford Coppola, Ben Bradlee, Arthur C. Clarke, Judy Collins, Joni Mitchell, Dinah Shore, politicians such as Mitch McConnell, Robert McNamara,  sports figures such as Jack Nicklaus,  Wilma Rudolph, visual artists such as Frida Kahlo, Anthony Armstrong-Jones,  Dorthea Lange, and writers such as Sir Walter Scott.

Jazz musician David Sanborn 

Fortunately most people who are infected with the polio virus do not even have any symptoms.  About 90% of persons infected do not even notice anything, and they become thus "naturally" immune.   How do we know this?  Because we can detect antibodies to the virus in persons who have been exposed to the disease.  Others, perhaps 4-8% develop a sore throat, a fever, and cold-like symptoms. 

Violinist Itzhak Perlman

Again such illnesses pass away with hardly anything more than a little rest and recuperation.    In 3% of cases, the virus enters the central nervous system and causes a kind of viral meningitis which can lead to headache, pain in the arms and legs (extremities), nausea and back pain.    Even then most of these do not lead to permanent damage.  It is only in 1 to 5 in a 1000 cases that lead to what is known as paralytic polio.  In such cases the muscles become poorly controlled up to what is known as acute flaccid paralysis.   It can affect the muscles of the legs and arms, and those of breathing. Itzhak Perlman suffered polio as a young person and is  seated when performing because of the after-effects.   These effects can be transitory or permanent. Jazz musician David Sanborn spent a year in an iron lung, but recovered. 

The Iron Lung ward of  Rancho Los Amigos Hospital (1953)

A small fraction of these patients end up in bulky respirators, iron lungs, for the duration of their natural lives. 




The virus we now know is an RNA virus which has been endemic among humans for the whole of human history, but it has been only in the last sixty or seventy years that some understanding has been gained of how it spreads and how it causes disease.


The virus propagates itself by infecting the cells of the mucosal lining of the gastrointestinal tract.  Like all viruses this involves hijacking the cellular machinery and multiplying inside cells, then spreading to other cells nearby.  The virus has a preference for motor neurons, which control the muscles and result in an inflammatory response that causes much tissue damage which may or may not be remediable.  If it spreads to the central nervous system it can infect the spinal cord affecting the muscles controlling the legs, or, far enough up the spinal cord, the nerves that control breathing, which can be rapidly fatal.  

It is an old story, the wrong bug in the wrong place can lead to disaster. 

The Central Nervous System is protected from intrusion by certain hydrophilic drugs, bacteria, and antibodies.   The blood brain barrier protects the brain from certain undesirable things such as infectious agents, but it isn't perfect.  If a virus gains access through neurons or a bacterium like Hemophilus influenzae gets into the cerebro-spinal fluid it can cause serious and largely irreparable damage to the brain and the nervous system.  Also, while the blood brain barrier prevents invasion by certain agents it also complicates delivery of certain chemotherapeutic drugs such as antibiotics.  While the brain and nervous system can recover somewhat from certain kinds of injuries, it is far less capable of healing than other tissues.  

The Salk and Sabin vaccines developed in the 1950s were a godsend to a largely defenseless public.  The polio virus is highly communicable and is often transmitted through the fecal-oral route.  That is to say, all it takes is contact with contaminated water or the exudate from someone else's infection to contract the disease.  Once the virus makes contact with the oral or intestinal mucosal cells, it may or may not go farther.  The human body can be viewed as a donut, basically. 

The top of the donut is the mouth, the bottom of the donut, the anus, and the outside of the donut the skin. The hole in the donut is the digestive tract. The polio virus attacks the inside of the donut.  

 The Immune system is charged with preventing attack from outside the body, which is not only the defensive perimeter known as our skin, but also the one known as our digestive tract, which presents an even greater problem since the body constantly has to decide whether something is food, waste, or some  living thing it is okay with or a living thing it definitely doesn't want.  Furthermore it has to determine what is part of the body and what doesn't belong there.  Confusion leads to all sorts of problems:  destruction of body structures or the gaining of admission to the inner sanctum by viruses and bacteria that are definitely up to no good.   Other bacteria are beneficial and keep the bad ones out, however as mentioned above, even innocuous bacteria, when in the wrong place, can wreak havoc.  

Vaccines only work, of course, before the virus has infected the body.  The concept is simple enough.  Expose the immune system to the organism in a such a way that it "remembers" it if it sees it a second time, but not in such a way as to cause the disease in the first place.  Suffering a disease and recovering from it is the hard way to gain immunity, but is often a very effective way of to ensure that the organism never gets another chance.  Once one has had polio, you aren't going to get it a second time, but this may be scant comfort if you have lost the use of your legs. 

The Salk vaccine was an "inactivated" (killed)  virus, which was shown to be effective.    The only problem was that the immune system tends not to take seriously non-living material unless it is presented along with something that will excite it in the right way.   And sometimes if you present material to the immune system in the wrong way you won't get a response at all, and will get a suppression of any immune response, which could be even worse.  To be effective the Salk vaccine had to be given more than once over a period of time.

The Sabin vaccine which came along a few years later was a "live" but weakened version of the polio virus.

  This is the one I remember taking back in the early 1960s.  Because the virus is actually alive and causes an infection, it is much better at getting the attention of the immune system.  The idea is, you get a mild case of the disease, without symptoms and you are immune for life to any more virulent form of the virus.  So one day I went at an appointed time to an elementary school where they were giving out sugar cubes with a dollop of virus containing material on the inside.   Not only were you rendered immune, but you could also pass the weakened virus to all your friends, acquaintances even if they happen to be Jehovah's witnesses or Mennonites and have a religious objection to vaccination. 

http://blogs.cdc.gov/publichealthmatters/2012/04/vaccines-test-your-knowledge-2/

 

This is referred to as "herd immunity", which is to say, children, being naturally rather unsanitary beings, tend to pass along to all the other kids any particular germs they happen to have acquired.  Unfortunately such vaccines are not as safe as giving the killed Salk virus and in rare instances the vaccine itself can cause paralytic disease.  For this reason in the US and the UK the live oral polio vaccine is no longer used, since the relative risk of a bad response to the live vaccine outweighs the health benefits as polio has been eradicated from the US and Europe.  

If you are, perversely, in search of the wild polio virus you would have to go to either Pakistan, Afghanistan, or Nigeria. In Nigeria for religious reasons, vaccination has not been allowed.