By Stan Deresinski, MD, FIDSA
Synopsis: The Centers for Disease Control and Prevention investigated the cases of two patients: a child with meningoencephalitis due to Naegleria fowleri and a man with Acanthamoeba granulomatous encephalitis. Both were associated with exposure to water and both were fatal.
Sources: Dulski TM, Montgomery F, Ramos JM, et al. Fatal case of splash pad-associated Naegleria fowleri meningoencephalitis — Pulaski County, Arkansas, September 2023. MMWR Morb Mortal Wkly Rep. 2025;74(10):167-172.
Haston JC, Ali IK, Roy S, et al. Notes from the Field: Fatal Acanthamoeba encephalitis in a patient who regularly used tap water in an electronic nasal irrigation device and a continuous positive airway pressure machine at home — New Mexico, 2023. MMWR Morb Mortal Wkly Rep. 2025;74(10):179-180.
Dulski and colleagues report the case of a previously healthy 16-month-old child admitted to a hospital in Arkansas with a three-day history of fever, vomiting, and altered mental status. Non-contrast computed tomography (CT) identified the presence of ventriculomegaly. The results of cerebrospinal fluid (CSF) examination appeared compatible with bacterial infection with 390 nucleated/μL with 71% neutrophils, protein 610 mg/dL, glucose < 4 mg/dL, but with 5,150 erythrocytes/μL. Empiric antibacterial and antiviral therapy was initiated, but no organism was detected using a commercial multiplex meningitis/encephalitis panel, and cultures were negative. However, two days later, pathology review of a Wright-Giemsa stain of CSF identified the presence of amoebic organisms thought to be consistent with Naegleria fowleri. Attempted therapy directed at this organism was initiated: amphotericin B, azithromycin, fluconazole, miltefosine, and rifampin, as well as dexamethasone. Despite this, the patient died on the following day.
Two to three days before symptom onset, the child had played at a splash pad, described by the Centers for Disease Control and Prevention (CDC) as “an interactive water play venue that sprays or jets water on users and has little or no standing water.” Investigation of the splash pad found that the water was inadequately disinfected. The splash pad was disabled and removed from use.
Haston et al report the case of a 66-year-old man who was admitted to a hospital in New Mexico with weakness and altered mental status with the subsequent development of fever and seizures, as well as respiratory and gastrointestinal complications. Brain lesions were detected on imaging. He died, and postmortem examination identified the presence of granulomatous amebic meningoencephalitis.
The patient had diabetes mellitus, alcohol use disorder, ulcerative colitis, and obstructive sleep apnea. Although he had had no recreational water exposure, he used an electronic nasal irrigation device and a continuous positive airway pressure (CPAP) machine at home, for both of which he used tap water.
Examination of brain tissue at CDC confirmed the presence of Acanthamoeba by immunohistochemical and polymerase chain reaction (PCR) testing. The organism also was cultivated from the nasal irrigation device and from the CPAP drained water receptacle, with PCR confirmation.
Commentary
Amoeba that survive in the environment and do not require a host are considered free-living. Those causing central nervous system (CNS) disease in humans include Acanthamoeba and Balamuthia, which cause granulomatous encephalitis, and Naegleria, which causes acute meningoencephalitis. Another is Sappinia, for which only very rare single case reports are available.
The case of Naegleria infection described earlier demonstrates the typical presentation resembling an acute, rapidly progressive bacterial meningitis. Infection most often occurs after swimming in fresh water, with the organism believed to gain entry through the nose. It also has been associated with nasal irrigation with tap water, including as a part of religious rituals. This is the third case associated with splash pads.
The diagnosis often is missed or delayed, and in this case it was made by pathological examination of CSF two days after presentation. Although multiple medications were administered (a regimen apparently recommended by the CDC), the patient died the following day — a not unusual occurrence since there have been only five (< 3%) survivors of this infection.1 An additional investigational agent, nitroxoline, is available from the CDC.
Acanthamoeba is perhaps best known as a cause of keratitis in contact lens wearers. As in the case discussed here, water is a potential source of infection, with nasal irrigation with tap water being the culprit event. The presentation of granulomatous encephalitis caused by this organism (or to Balamuthia) is, in contrast to Naegleria infection, subacute, with symptoms sometime present for weeks.2 Clinically and radiographically, presentation more closely resembles that of a brain abscess, and diagnosis in life often requires brain biopsy. Excision may be performed; recommended chemotherapy is the same as for Naegleria infection.
My experience with these infections has, fortunately, been limited. Decades ago in Florida, I was asked to consult on a case of Naegleria meningoencephalitis in which the diagnosis had been made by an alert technician at a local hospital. Keeping the slide warm, he identified directional motility along with pseudopod formation. Nonetheless, the patient died. The child had acquired the infection swimming in a lake in Central Florida, a state whose lakes frequently harbor the organism.
At Stanford, we once identified a fatal case of Acanthamoeba encephalitis in a patient with a total artificial heart.3 We reported two acquired immunodeficiency syndrome (AIDS) patients with disseminated Acanthamoeba infection. Both were fatal despite attempted therapeutic intervention.4
Stan Deresinski, MD, FIDSA, is Clinical Professor of Medicine, Stanford University.
References
1. Hall AD, Kumar JE, Golba CE, et al. Primary amebic meningoencephalitis: A review of Naegleria fowleri and analysis of successfully treated cases. Parasitol Res. 2024;123(1):84.
2. Kalra SK, Sharma P, Shyam K, et al. Acanthamoeba and its pathogenic role in granulomatous amebic encephalitis. Exp Parasitol. 2020;208:107788.
3. Tan SK, Gajurel K, Tung C, et al. Fatal acanthamoeba encephalitis in a patient with a total artificial heart (syncardia) device. Open Forum Infect Dis. 2014;1(2):ofu057.
4. Sison JP, Kemper CA, Loveless M, et al. Disseminated acanthamoeba infection in patients with AIDS: Case reports and review. Clin Infect Dis. 1995;20(5):1207-1216.
The Centers for Disease Control and Prevention investigated the cases of two patients: a child with meningoencephalitis due to Naegleria fowleri and a man with Acanthamoeba granulomatous encephalitis. Both were associated with exposure to water and both were fatal.
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