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Naegleriasis: causes, symptoms, diagnosis, treatment
Last reviewed: 05.07.2025
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[ Epidemiology of negleriosis
Naegleria most often infects young people and children, mainly when swimming in open water, pools and hot tubs. Apparently, this is due to the presence of flagellate stages of development in Naegleria, which are found in water, which facilitates human contact with the amoebas.
Naegleria cysts can also penetrate the nasal cavity when inhaling aerosols containing them. Naegleria are quite widespread, but are more common in areas with tropical and subtropical climates. Up to 1985, the literature provided information on 128 cases of CNS naegleriasis in the world, of which 50 were registered in the USA.
What causes Naegleriasis?
Naegleria is a free-living amoeba, in the life cycle of which there are 3 morphological forms: amoeboid trophozoite, flagellate stage and cyst. The size of trophozoites is 15-40 μm. Vigorous pulsation of the contractile vacuole distinguishes it from the host cells. The nucleus (5 μm) has an endosome. Pseudopodia are transparent and wide. Like all amoebae, the cytoplasm is divided into ecto- and endoplasm, but Naegleria have a lamellar Golgi complex, pronounced endoplasmic reticulum and a contractile vacuole. Cysts are round, with a smooth double wall, 10-20 μm in size.
Biology of negleriosis
N. fowleri is a free-living amoeba that lives in freshwater bodies (wastewater, swimming pools, thermal springs, etc.). When the temperature rises to 35 °C, Naegleria begin to actively reproduce, and their numbers increase significantly. Some amoebas, with sharp fluctuations in temperature and changes in the pH of the environment, form two flagella and actively swim in the water column for 24 hours, then again turn into an amoeboid form.
When unfavourable conditions occur, amoebas easily encyst. Unlike acanthamoebas, Naegleria cysts are less resistant to drying out.
Pathogenesis of Naegleriasis
Human infection with amoebas apparently occurs when they enter the oral and nasal cavities with contaminated water. From the nasopharynx, through the olfactory epithelium, the amoebas penetrate into the richly vascularized subarachnoid space, from where they spread to all parts of the brain. In the brain tissue, they localize around blood vessels and rapidly multiply. As a result, hemorrhages and necrosis occur in both the gray and white matter of the brain. Primary amoebic meningoencephalitis develops.
Symptoms of Naegleriasis
Incubation period of Naegleriasislasts 2-3 days, less often 7-15 days. The onset of the disease is sudden. At first, there are often disturbances in taste or smell. Symptoms of naegleriasis appear: headaches, high fever, nausea, vomiting, convulsions. Rigidity of the occipital muscles is noted. Ulcers often form on the mucous membrane of the pharynx. Neurological symptoms of naegleriasis are revealed due to meningitis and encephalitis. Pulmonary edema develops. Coma soon sets in. In most cases, within a week after the appearance of the first symptoms, patients die due to pulmonary edema and respiratory arrest. N. fowlen, like acanthamoeba, can cause lesions of the skin, lungs and eyes.
Complications of Naegleriasis
The most serious complication of naegleriasis is the development of meningoencephalitis as a result of the dissemination of pathogens from the primary lesion on the skin or eye into the central nervous system.
Diagnosis of negleriosis
Clinical diagnosis of Naegleriasis is complicated by the similarity of symptoms of primary amoebic brain damage with meningitis and meningoencephalitis of bacterial or viral etiology. Anamnesis data are taken into account (bathing in silty warm water bodies, contact with sewage, etc.). The final diagnosis of primary amoebic meningoencephalitis is established microscopically upon detection of N. fowlen in the cerebrospinal fluid sediment or in brain biopsy specimens. They differ from surrounding cells by their mobility. The culture method is also used. Naegleria are aerobic organisms; like Acanthamoeba, they can grow on simple agar on which the bacteria have been previously inoculated. When water is added to the Naegleria culture, flagellates are formed, which serves as their distinguishing feature from Acanthamoeba. Differential diagnosis of Naegleriasis with CNS damage is carried out with encephalitis and meningitis of other etiologies.
What do need to examine?
What tests are needed?
Treatment of negleriosis
Treatment for Naegleriasis has not been developed. Amphotericin B is used at a dose of 0.25-1.5 mg/kg/day intravenously by drip, subarachnoidally or directly into the cerebral ventricles. Sometimes it is administered in combination with miconazole and (or) rifampin. Intravenous injections of sulfadiazine (0.5 g/day), chloramphenicol (2-4 million IU/day) are used. Anticonvulsants, glucocorticoids, etc. are used as symptomatic agents. After Naegleriasis meningitis, only patients who received amphotericin B survived.
Naegleriasis has an unfavorable prognosis when the central nervous system is affected.
How to prevent Naegleria?
Prevention of Naegleriasis consists of following the rules of personal hygiene. Particular attention is paid to preventing infection when swimming in pools and open water bodies where the water temperature is 35 °C or more.