Primary amebic meningoencephalitis (PAM) and guidelines

Primary amebic meningoencephalitis (PAM) is a rare and usually deadly disease caused by infection with the ameba (Naegleria fowleri). The pathogenic potential in a human host was first described in 1965; the first reported case of PAM in Texas occurred in 1972, according to the Texas Department of State Health Services.

Lake LBJ

In August 2007, a 12-year-old boy became ill with PAM after spending two previous weeks at a summer camp on Lake LBJ. He was admitted to a hospital on Aug. 10 and, after being diagnosed with PAM, died Aug. 15. A second case involved a 22-year-old Lubbock man who contracted PAM after a trip to Lake LBJ on the weekend of Aug. 24. He reportedly sustained a ruptured eardrum while wake boarding. He was admitted to a Lubbock hospital on Aug. 31 and died Sept. 4. Both cases were confirmed by the Department of State Health Services.

Naegleria fowleri

According to information provided by the Department of State Health Services, the ameba that causes the infection lives in soil and in freshwater ponds, lakes, rivers, poorly or nonchlorinated pools, discharge or holding basins, and hot springs throughout the world. Naegleria thrives in warm, stagnant bodies of fresh water when temperatures are above 80 degrees. Consequently, cases of the disease usually occur from June through September. When water temperatures are below 80 degrees, the ameba exists in a cyst form that is not capable of causing infection. Naegleria fowleri is unique in that it exists in two different forms – pseudopod and flagellated. Transformation of ameba into flagellates is a distinctive feature of Naegleria.

Although the ameba is commonly found in the environment, cases of PAM are very rare. In the last 30 years, only a few hundred cases have been reported worldwide. Twenty-four infections were documented in the United States between 1989 and 2000. Prior to 2007, there were 34 cases of PAM in Texas since 1972, all fatal. The last reported case in Texas was in 2005 from Lake Somerville. One previous PAM case involving the Highland Lakes has been reported in the past. In 1980, a 23-year-old female died after water skiing on Lake Austin.

According to Florida health officials, 46 percent of the lakes tested in Florida have the pathogenic amebae, and it is believed that an all-inclusive study would reveal that most state lakes harbor the organism. From 1962 to 2000, 18 cases had been documented in Florida, most originating from the central region of the state. There have been three reported cases in Florida this year.

Symptoms:

Onset symptoms of infection start 1 to 14 days after exposure. The initial symptoms include, but are not limited to changes in taste and smell, also 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 3 to 7 days, with death occurring from 7 to 14 days.
Clinical Manifestation:

Acanthamoeba species and Balamuthia mandrillaris usually act as opportunistic pathogens in immunocompromised or debilitated individuals in whom they cause pneumonitis or dermal ulcerations. From these lesions the amebas may spread to the brain to cause an insidious, slowly progressive, and usually fatal encephalitis called granulomatous amebic encephalitis. In healthy individuals, Acanthamoeba spp can cause an ulcerating keratitis, which is often associated with the use of improperly sterilized contact lenses.
Immunoassays and antibodies:

Naegleria fowleri, a free-living amoeba widely distributed in soil and water, is the causative agent of primary amoebic meningoencephalitis, a human fatal disease.The N.fowleri species has been isolated from swimming pools, freshwater lakes, thermal springs, freshwater habitats, polluted waters.Therefore, on a public health point of view, it is important to identify aeras containing N.fowleri.Specific methods are required, due to the large homology existing between N.fowleri and other non pathogenic forms of Naegleria.