Chapter 5 - 4

04 Environmental Science

Naegleria fowleri Outbreak

In 2007, the number of reported cases of deaths caused by Naegleria fowleri, a rare amoeba that primarily resides in soil, sharply increased in the United States.

The amoeba was found in warm bodies of water such as freshwater lakes and ponds that range from twenty-five to thirty-five degrees Celsius.

N.fowleri was detected not only in freshwater sources, but increasingly so in domestic water supplies, groundwater supplies, and recreational water sources as well.

Investigations by environmental scientists were carried out in order to determine the causes of the outbreaks, which were linked to warm water stagnation, the amoeba’s ability to propagate, and sudden changes in environments.

The amoeba attacks the human central nervous system by entering via the mucous membranes of the nasal passageway.

When it reaches the olfactory bulbs through the nose, it causes hemorrhaging, which is the loss of blood, and necrosis, which is the death of living tissues and cells.

From the olfactory bulbs, it reaches the brain by traveling along nerve fibers.

One of the first symptoms to emerge is a noticeable change in the ability to smell and taste; following that, vomiting and nausea, headaches and fevers, and ultimately, coma and death will ensue.

N.fowleri became an immediate concern as the frequency of reported cases increased in the United States.

Between 1995 and 2004, the US Centers for Disease Control and Prevention determined that twenty-three N. fowleri-caused deaths took place in the United States.

In 2007, a sharp increase was noted: six cases were reported in the United States that year, marking almost a 250 percent increase in reported cases.

Scientists struggled to determine the cause.

Water stagnation was suggested as a cause after researchers determined that N. fowleri could be found even in domestic dwellings.

In an experiment conducted by Francine Marciano-Cabral, samples were collected from homes in an Arizona town where two boys had died due to an infection with N.fowleri.

It was discovered that seventeen of nineteen sites tested positive for the amoeba, particularly in the residual water in the sink pipes.

It has been speculated that the two boys, who had had no history of freshwater swimming but had taken regular baths, died due to the presence N. fowlerl in the water supply of their homes.

The researchers suggest that N.fowleri can proliferate in the stagnant parts of home water supplies, which was probably the case in this incident.

Other research conducted in the southwestern state of Arizona showed that groundwater supplies were contaminated with N.fowleri.

Of the 188 wells sampled, sixteen percent tested positive for the presence of the amoeba.

These were not private wells but rather high-volume public wells run by private water companies and municipal facilities.

The researchers also found that a certain kind of bacteria, called heterotrophic bacteria, was present in the water.

These bacteria served as food for N.fowleri, allowing them to propagate in water supplies that were usually free of such bacteria and, thus, free of N.fowieri.

The researchers concluded that the presence of these bacteria allowed N.fowleri to invade the municipal water supplies.

They also discovered that N.fowleri is very resistant to the purification treatments common in municipal treatment plants, including treatment with chlorine.

Therefore, the treatments widely used to remove harmful organisms from water futile against N.fowleri.

In an experiment by Detterline and Wilhelm, the presence of N. fowleri in government-owned recreational waters was linked with changes in the environment.

Fifty-nine sites were tested for N.fowleri, of which thirty-four tested positive.

These sites include Yosemite Creek of Yosemite National Park and other federal water sources-throughout the United States.

The investigation found that the presence of this amoeba was highly correlated with environmental disturbances, such as unnaturally high, iron content (usually due to limited outlets), disruptions in biodiversity, land clearings, or fluctuations in water temperatures.

The experiment found that the amoeba was especially tolerant of waters above twenty-six degrees Celsius.

Thus, the amoeba’s presence can be connected to the increase in water temperatures across the United States as global warming continues to alter ecosystems.