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. 2021 Jul 1;73(1):e19-e27.
doi: 10.1093/cid/ciaa520.

Epidemiology and Clinical Characteristics of Primary Amebic Meningoencephalitis Caused by Naegleria fowleri: A Global Review

Radhika Gharpure  1   2 , John Bliton  1 , Alexandra Goodman  1 , Ibne Karim M Ali  1 , Jonathan Yoder  1 , Jennifer R Cope  1
Affiliations

Epidemiology and Clinical Characteristics of Primary Amebic Meningoencephalitis Caused by Naegleria fowleri: A Global Review

Radhika Gharpure et al. Clin Infect Dis. .

Abstract

Background: Primary amebic meningoencephalitis (PAM) is a rapidly progressive and often fatal condition caused by the free-living ameba Naegleria fowleri. To estimate the global occurrence, characterize the epidemiology, and describe the clinical features of PAM, we report a series of PAM cases published in the international literature and reported to the Centers for Disease Control and Prevention (CDC).

Methods: We performed a literature search of PAM case reports published through 2018. Additionally, we included cases reported through the CDC's Free-Living Ameba surveillance or diagnosed via CDC's Free-Living and Intestinal Amebas Laboratory. Cases were classified as confirmed, probable, or suspect on the basis of confirmatory testing, presentation, exposure, and disease course.

Results: A total of 381 PAM cases were identified. Seven reported survivors were classified as confirmed. The most commonly reported exposure associated with PAM was swimming/diving, and the most common class of water source was lakes/ponds/reservoirs. Patients were predominantly male (75%), with a median age of 14 years. Confirmed and probable cases were similar in their survival, course of illness, and cerebrospinal fluid (CSF) findings.

Conclusions: PAM is a rare but deadly disease with worldwide occurrence. Improved clinician awareness, resulting in earlier diagnosis and treatment, may contribute to increased survival among PAM patients. The case definition of probable used in this study appears to capture cases of PAM, as evidenced by similarities in outcomes, clinical course, and CSF profile to confirmed cases. In the absence of confirmatory testing, clinicians could use this case definition to identify cases of PAM.

Keywords: Naegleria fowleri; free-living ameba; primary amebic meningoencephalitis.

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Conflict of interest statement

Potential conflicts of interest. The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest.

Figures

Figure 1.
Figure 1.
Reported cases of primary amebic meningoencephalitis (n = 381) by country of exposure. No cases were reported from the US states of Alaska and Hawaii nor from countries not pictured in the Western Pacific Region.
Figure 2.
Figure 2.
Reported cases of primary amebic meningoencephalitis (n = 381) by case year and classification. Negative binomial regression was restricted to 1965 (the year of the first published case report [12]) through 2016 (accounting for the median 2-year delay to publication). Cases that occurred in 2017 and 2018 were likely underreported due to this delay in publication.
Figure 3.
Figure 3.
Reported cases of primary amebic meningoencephalitis (n = 283) by case year and timing of diagnosis (antemortem vs postmortem). Negative binomial regression was restricted to 1965 (the year of the first published case report [12]) through 2016 (accounting for the median 2-year delay to publication). Cases that occurred in 2017 and 2018 were likely underreported due to this delay in publication.
See this image and copyright information in PMC

References

    1. Visvesvara GS, Moura H, Schuster FL. Pathogenic and opportunistic free-living amoebae: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea. FEMS Immunol Med Microbiol 2007; 50:1–26. - PubMed
    1. Ma P, Visvesvara GS, Martinez AJ, Theodore FH, Daggett PM, Sawyer TK. Naegleria and Acanthamoeba infections: review. Rev Infect Dis 1990; 12:490–513. - PubMed
    1. John DT. Primary amebic meningoencephalitis and the biology of Naegleria fowleri. Annu Rev Microbiol 1982; 36:101–23. - PubMed
    1. Visvesvara GS. Amebic meningoencephalitides and keratitis: challenges in diagnosis and treatment. Curr Opin Infect Dis 2010; 23:590–4. - PubMed
    1. Visvesvara GS, Peralta MJ, Brandt FH, Wilson M, Aloisio C, Franko E. Production of monoclonal antibodies to Naegleria fowleri, agent of primary amebic meningoencephalitis. J Clin Microbiol 1987; 25:1629–34. - PMC - PubMed