Rare Naegleria fowleri meningoencephalitis diagnosed via combined molecular biology and metagenomic sequencing techniques: a case report

Abstract

Background: Naegleria fowleri, a pathogenic free-living amoeba, causes primary amoebic meningoencephalitis (PAM), a rare but devastating disease with acute onset, rapid progression, and > 95% mortality. Despite its rarity, the catastrophic outcomes associated with this infection underscore the critical importance of prevention. In this report, we present a rare pediatric fatality caused by PAM in China, highlighting the challenges of diagnosis and treatment.

Case presentation: A 6-year-old child from Lushan County, Henan Province, developed persistent high fever, headache, vomiting, and altered mental status on December 5, 2024. After receiving ineffective local treatment, the child was transferred to the Eastern District of Henan Children's Hospital on December 7 for further evaluation and management. Upon admission, cerebrospinal fluid was collected for laboratory analysis, and antimicrobial therapy, including amphotericin B, fluconazole, and rifampicin, was promptly initiated. Despite these interventions, the patient's condition deteriorated rapidly, and the child succumbed to the infection on December 9.

Conclusions: Clinical and laboratory findings strongly suggest that the child was infected with N. fowleri, resulting in PAM. Epidemiological investigation suggests possible exposure at a public bathhouse. Given the survival characteristics of the N. fowleri and potential habitat expansion due to global warming, this sporadic case underscores PAM's lethal potential. With mortality exceeding 95%, early recognition and prompt intervention are crucial. Clinicians should maintain high suspicion for PAM in patients with compatible symptoms, especially in regions with warm freshwater exposure.

Keywords: Naegleria fowleri; Genetic analysis; Metagenomic sequencing; Primary amoebic meningoencephalitis.

Fig. 1

Neighbor-Joining Tree inferred from partial 18S rRNA sequences (1,843 bp) from mNGS analysis of N. fowleri

Fig. 2

Agarose gel electrophoresis of PCR amplification products from the cerebrospinal fluid sample using species- and genus-specific primers for Naegleria. M, DNA marker; lanes 1–4, PCR products from the patient’s cerebrospinal fluid sample

Fig. 3

Phylogenetic tree of Naegleria species based on ITS gene region sequences, constructed using the NJ method. The numbers at the nodes indicate the percentage bootstrap values from 1000 replicates, with only values greater than 50% shown. GenBank accession numbers are indicated before the species names

Fig. 4

Morphology of amoebic cysts in the patient’s cerebrospinal fluid stained with iodine solution. 400 × , Scale Bar = 20 μm