Primary Amebic Meningoencephalitis Related to Groundwater in Costa Rica: Diagnostic Confirmation of Three Cases and Environmental Investigation

Lissette Retana Moreira,Elizabeth Abrahams Sandí,Silvia Elena Molina Castro,Leidy Zamora Rojas,Muriel Grijalba Murillo

doi:10.3390/pathogens9080629

Lissette Retana Moreira, Elizabeth Abrahams Sandí + Show 3 more

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https://doi.org/10.3390/pathogens9080629

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Abstract

During the first trimester of 2020, the Ministry of Health of Costa Rica reported the first three cases of primary amebic meningoencephalitis (PAM). In two cases, laboratory personnel of the hospitals preliminarily identified amoeboid forms in cerebrospinal fluid (CSF) samples. For the molecular confirmation of species, CSF samples were sent to our laboratory. We carried out microscopic analyses and exflagellation assays. Besides, samples were cultured in 2% casein hydrolysate medium and in non-nutrient agar plates supplemented with Escherichia coli. Finally, PCR and sequencing were employed for the molecular diagnosis and species identification. In all cases, the presence of Naegleria fowleri was confirmed. An environmental investigation to identify the possible infection sources was also performed. Water samples from hot springs and groundwater from an artisan well were collected and after filtration and culture in non-nutrient agar plates supplemented with E. coli, thermotolerance and exflagellation assays were carried out. For the positive samples, PCR and sequencing were performed, confirming the presence of N. fowleri in several water samples. The report of these cases and the possible association with hot springs has had a significant impact on the population and health authorities of Costa Rica.

Highlights

Primary amebic meningoencephalitis (PAM) is an acute disease of rapid progression of the central nervous system caused by the thermophilic free-living amoeba Naegleria fowleri
Epidemiologic studies of PAM indicate an estimate of 300–440 cases worldwide [3,6], with more than one third of the cases diagnosed in the United States [7]
This number may not exactly reflect the real number as some researchers propose an underestimation of the disease of up to 50% in this country, even when using well-established diagnostic methodologies and researchers with huge knowledge in different aspects related to PAM

Summary

Introduction

Primary amebic meningoencephalitis (PAM) is an acute disease of rapid progression of the central nervous system caused by the thermophilic free-living amoeba Naegleria fowleri. The infection usually occurs when water with the amoebae enters the nose and gains access to the brain, migrating along the olfatory nerves through the cribriform plate [1]. The incubation period varies from 2 to 15 days and death typically occurs 3–7 days after the onset of symptoms [2]. Infections with N. fowleri are fatal in more than 95% of cases and until 2016, more than 300 cases of PAM were reported worldwide [3]. Most PAM cases are associated with exposure to warm, untreated freshwater while participating in recreational water activities such as swimming and diving [1].

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