CNN News

Zachary Reyna, a 12-year-old Florida boy stricken with a brain-eating parasite, has died. Zachary's family told CNN, believe that the boy who they described as an active seventh grader was infected while knee boarding with friends in a water-filled ditch by his house on August 3. Officials warn of brain-eating amoeba, after he was hospitalized, the boy underwent brain surgery, and doctors diagnosed him with primary amoebic meningoencephalitis.

The first symptoms of primary amoebic meningoencephalitis appear one to seven days after infection, including headache, fever, nausea, vomiting and a stiff neck, according to the Centers for Disease Control and Prevention. "Later symptoms include confusion, lack of attention to people and surroundings, loss of balance, seizures and hallucinations," the agency website says. "After the start of symptoms, the disease progresses rapidly and usually cause death within one to 12 days."

Florida issues warning about rare, brain-eating amoeba

Naegleria fowleri - Brain-Eating Amoeba

Ravi Kumudesh / Sri Lanka Society for Medical Laboratory Science

Naegleria fowleri, popularly known as the "brain-eating amoeba", is a free-living excavates form of protist typically found in warm bodies of fresh water, such as ponds, lakes, rivers, and hot springs. It is also found in soil, near warm-water discharges of industrial plants, and unchlorinated or poorly chlorinated swimming pools in an amoeboid or temporary flagellate stage. 

There is no evidence of this organism living in salt water. It is an amoeba belonging to the groups Percolozoa or Heterolobosea. N. fowleri can invade and attack the human nervous system. Although this occurs rarely, such an infection nearly always results in the death of the victim. The case fatality rate is estimated at 98%.

Signs and Symptoms

Onset symptoms of infection start about five days (range is from one to seven days) after exposure. The initial symptoms include, but are not limited to, changes in taste and smell, headache, fever, nausea, vomiting, and stiff neck. Secondary symptoms include confusion, hallucinations, lack of attention, ataxia, and seizures. After the start of symptoms, the disease progresses rapidly over three to seven days, with death occurring from seven to fourteen days after exposure.

Causes

In humans, N. fowleri can invade the central nervous system via the nose. The penetration initially results in significant necrosis of and hemorrhaging in the olfactory bulbs. From there, the amoeba climbs along nerve fibers through the floor of the cranium via the cribriform plate and into the brain. The organism begins to consume cells of the brain piecemeal by means of a unique sucking apparatus extended from its cell surface. It then becomes pathogenic, causing primary amoebic meningoencephalitis (PAM). PAM is a syndrome affecting the central nervous system. 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 effective against N. fowleri in vitro, but the prognosis remains bleak for those who contract PAM, and survival remains less than 1%. On the basis of the in vitro evidence alone, the CDC currently recommends treatment with amphotericin B for primary amoebic meningoencephalitis, but no evidence supports this treatment affecting outcome. Treatment combining miconazole, sulfadiazine, and tetracycline has shown limited success only when administered early in the course of an infection.

While miltefosine had therapeutic effects during an in vivo study in mice, chlorpromazine showed to be the most effective substance the authors concluded: "Chlorpromazine had the best therapeutic activity against N. fowleri in vitro and in vivo. Therefore, it may be a more useful therapeutic agent for the treatment of PAM than amphotericin B.

Untimely diagnoses remain a very significant impediment to the successful treatment of infection, as most cases have only been discovered post mortem. Infection killed 121 people in the United States from 1937 through 2007.

Life cycle

Biotic phases:

Naegleria fowleri occurs in three forms:

   cyst,

   flagellate,

   trophozoite

Cyst stage

Trophozoites encyst due to unfavorable conditions. Factors that induce cyst formation can include food deprivation, crowding, desiccation, accumulation of waste products, and cold temperatures. N. fowleri has been found to encyst at temperatures below 10 °C/50F.

Trophozoite stage

The trophozoites are characterized by a nucleus and a surrounding halo. They travel by pseudopodia, temporary round processes which fill with granular cytoplasm. The pseudopodia form at different points along the cell, thus allowing the trophozoite to change directions. In their free-living state, trophozoites feed on bacteria. In tissues, they phagocytize red blood cells and white blood cells and destroy tissue.

Flagellate stage

This biflagellate form occurs when trophozites are exposed to a change in ionic concentration, such as placement in distilled water. The transformation of trophozoites to flagellate form occurs within a few minutes.

Diagnosis

N. fowleri can be grown in several kinds of liquid axenic media or on non-nutrient agar plates coated with bacteria. Escherichia coli can be used to overlay the non-nutrient agar plate and a drop of cerebrospinal fluid sediment is added to it. Plates are then incubated at 37°C and checked daily for clearing of the agar in thin tracks, which indicate the trophozoites have fed on the bacteria. Detection in water is performed by centrifuging a water sample with E. coli added, 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.[13] Confirmation of Naegleria presence can be done by a so-called flagellation test, where the organism is exposed to a hypotonic environment . Naegleria, in contrast to other amoebae, differentiates within two hours into the flagellate state. Pathogenicity can be further confirmed by exposure to high temperature (42 °C): Naegleria fowleri is able to grow at this temperature, but the nonpathogenic Naegleria gruberi is not.

Sri Lanka Society for

Medical Laboratory Science

kumudeshr@gmail.com / 0094773077717