Naegleria fowleri

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Naegleria fowleri (pronounced //)(also known as the brain eating amoeba) is a free living amoeba typically found in warm fresh water, from 25–35 degrees Celsius (77–95 degrees Fahrenheit) in an amoeboid or temporary flagellate stage. It belongs to a group called the Percolozoa or Heterolobosea. N. fowleri can invade and attack the human nervous system; although this occurs rarely, such an infection will nearly always result in the death of the victim.

Infection

In humans, N. fowleri can invade the central nervous system via the nose, more specifically the olfactory mucosa and nasal tissues. The penetration initially results in significant necrosis of and hemorrhaging in the olfactory bulbs. From there, amoebae climb along nerve fibers through the floor of the cranium via the cribriform plate and into the brain. It then becomes pathogenic, causing primary amoebic meningoencephalitis (PAM or PAME). PAM is a syndrome affecting the central nervous system, characterized by changes in olfactory perception (taste and smell), followed by vomiting, nausea, fever, headache, and the rapid onset of coma and death in two weeks.PAM usually occurs in healthy children or young adults with no prior history of immune compromise who have recently been exposed to bodies of fresh water. Amphotericin B is currently the most effective known pharmacologic treatment for N. fowleri, but the prognosis remains bleak for those that contract PAM, as only eight patients have survived (3% survival rate) in a clinical setting. Amphotericin B devastates N. fowleri organisms in laboratory settings; it, in combination with systemic rifampicin, is the preferred choice in N. fowleri treatment. A more aggressive antibody serum-based treatment is being pursued, and may eventually prove more effective than modern broad-spectrum antibiotic targeting. Timely diagnosis remains a very significant impediment to the successful treatment of infection, as most cases have only been appreciated post-mortem. It killed 23 people in the US from 1995 to 2004, and has killed six in the year of 2007 (3 in Florida, 2 in Texas, and 1 in Arizona).

Detection

N. fowleri can be grown in several kinds of liquid axenic media or on non-nutrient agar plates coated with bacteria. Detection in water is performed by centrifuging a water sample with Escherichia coli added, and then applying the pellet to a non-nutrient agar plate. After several days the plate is microscopically inspected and Naegleria cysts are identified by their morphology. Final confirmation of the species' identity can be performed by various molecular or biochemical methods.

Incidents and outbreaks

  • Between years 1962–1965, 16 young persons died of acute meningoencephalitides in Ústí nad Labem as a consequence of bathing in a indoor swimming pool.
    • According to the Centers for Disease Control and Prevention, the amoeba killed 23 people between 1995 and 2004.
  • In August 2005, two Oklahoma boys, ages 7 and 9 were killed by N. fowleri after swimming in hot stagnant water of the lakes in the Tulsa area.
  • In 2007, six cases have been reported in the U.S. as of September, all fatal: Six Die From Brain-Eating Amoeba in Lakes, an Associated Press article via The Washington Post
  • In July, the amoeba caused the deaths of three boys in lakes around Orlando, Florida. Possible causes of the infections include higher temperature and droughts in that area of Florida.
  • In late summer, the amoeba caused the death of a 12-year-old boy and a 22-year-old young man in Lake LBJ in Texas.[http://www.cnn.com/2007/HEALTH/10/04/amoeba.lake/index.html]
  • In September, a 14-year-old boy was killed by the amoeba after likely having caught it while swimming in Lake Havasu in Arizona. The doctors suspected meningitis before the boy died, but did not know the etiology until the CDC confirmed it as N. fowleri.

    • Pop culture references

  • Naegleria fowleri was featured on the TV show House, in a two-part season 2 episode ("Euphoria" parts 1 and 2). The writers took dramatic license with one of the disease's symptoms. Both characters developed cortical blindness, a condition affecting the occipital lobes where the patient thinks he can see but really cannot. This is not consistent with N. fowleri, whose initial symptoms are "alteration in taste (ageusia) or smell (parosmia)".
  • A "brain-sucking amoeba" that infects swimmers was mentioned in the season 1 episode of The X-files, "Darkness Falls"


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