Primary amoebic meningoencephalitis

Primary amebic meningoencephalitis: a review of Naegleria fowleri and analysis of successfully treated cases

Primary amebic meningoencephalitis (PAM) is a necrotizing and hemorrhagic inflammation of the brain and meninges caused by Naegleria fowleri, a free-living thermophilic ameba of freshwater systems. PAM remains a neglected disease that disproportionately affects children in tropical and subtropical climates, with an estimated mortality rate of 95-98%. Due to anthropogenic climate change, the average temperature in the USA has increased by 0.72 to 1.06 °C in the last century, promoting the poleward spread of N. fowleri. PAM is often misdiagnosed as bacterial meningitis or viral encephalitis, which shortens the window for potentially life-saving treatment. Diagnosis relies on the patient's history of freshwater exposure and the physician's high index of suspicion, supported by cerebrospinal fluid studies. While no experimental trials have been conducted to assess the relative efficacy of treatment regimens, anti-amebic therapy with adjunctive neuroprotection is standard treatment in the USA. We performed a literature review and identified five patients from North America between 1962 and 2022 who survived PAM with various degrees of sequelae.

Case Report: Recognition of Devastating Primary Amoebic Meningoencephalitis (PAM) Caused by Naegleria fowleri: Another Case in South China Detected via Metagenomics Next-Generation Sequencing Combined With Microscopy and a Review

Introduction

Primary amoebic meningoencephalitis (PAM) caused by Naegleria fowleri is seldom reported in mainland China.

Methods

One case from South China was presented, and the clinical features of the PAM, especially the early CT features, were compared to those in the literatures from PubMed/Web of Science/China National Knowledge internet (CNKI).

Case Presentation and Results

A 47-year-old man with a high fever came to the fever clinic. Twelve hours later, the man lost consciousness and exhibited generalized tonic-clonic seizures and needed ventilator-controlled ventilation. Then, he was admitted to the neurology intensive care unit (NICU). The opening pressure of his cerebrospinal fluid (CSF) was over 500 mm H2O with highly increased leukocyte/protein levels and very low glucose levels. Three days after admission, high copy numbers of Naegleria fowleri amoebae were detected by metagenomics next-generation sequencing (mNGS) and cysts were visible with wet mount microscopy. Four days after admission, the patient experienced brain death. However, the relatives of the patient did not want to give up, and he received amphotericin B (AmB). During hospitalization, he suffered from severe damage to the liver and kidneys and electrolyte disorders that required continuous renal replacement therapy (CRRT).

Review

All 20 included PAM patients suffered from fever. Seventeen of them had headache and neck stiffness. Ten of them showed generalized brain edema. To date, 7 cases of PAM have been reported in China. Only one patient survived. Most of the patients showed generalized brain edema. Only the surviving patient showed focal edema. He died three months later.

Conclusion

Rapidly progressive meningoencephalitis in which the CSF results are similar to those suffered from a bacterial infection should be considered a possible case of PAM. It can be rapidly detected with microscopy in CSF wet mounts but needs further molecular investigation for confirmation, and mNGS should be a new method used for rapid and precise identification. Moreover, CRRT may prolong the survival time of PAM patients with multiple organ failure.

Understanding the true burden of "Naegleria fowleri" (Vahlkampfiidae) in patients from Northern states of India: Source tracking and significance

The present study is an attempt to investigate the presence of Naegleria fowleri in Indian population. A total of 307 patients were enrolled and water samples were collected from both residential and surrounding areas of patients found positive for N. fowleri. The different species of Naegleria from both clinical and water samples were identified taxonomically. Recommended microbiological conventional techniques were used to identify different Naegleria stages and other free-living amoebae from the samples. PCR assays, using both genus and species specific primers were also optimized. None of the samples were positive by conventional microbiological examinations. However, PCR assays detected only three samples positive for N. fowleri. A total of 10 water bodies (ponds), that were used by Naegleria positive patients were examined. The pH and temperature of the water samples collected from water bodies ranged between 5.6-7.2 and 25-32 °C respectively. Among all the 10 water samples tested, four samples were positive for genus Naegleria by PCR assay, of which only two samples, showed positive amplification for N. fowleri. The sequence analysis of N. fowleri strain belonged to genotype II.

Fatal primary amoebic meningoencephalitis in a Norwegian tourist returning from Thailand

INTRODUCTION

Primary amoebic meningoencephalitis (PAM) is a rare disease caused by the free-living amoeba Naegleria fowleri. Infection occurs by insufflation of water containing amoebae into the nasal cavity, and is usually associated with bathing in freshwater. Nasal irrigation is a more rarely reported route of infection.

CASE PRESENTATION

A fatal case of PAM in a previously healthy Norwegian woman, acquired during a holiday trip to Thailand, is described. Clinical findings were consistent with rapidly progressing meningoencephalitis. The cause of infection was discovered by chance, owing to the unexpected detection of N. fowleri DNA by a PCR assay targeting fungi. A conclusive diagnosis was established based on sequencing of N. fowleri DNA from brain biopsies, supported by histopathological findings. Nasal irrigation using contaminated tap water is suspected as the source of infection.

CONCLUSION

The clinical presentation of PAM is very similar to severe bacterial meningitis. This case is a reminder that when standard investigations fail to identify a cause of infection in severe meningoencephalitis, it is of crucial importance to continue a broad search for a conclusive diagnosis. PAM should be considered as a diagnosis in patients with symptoms of severe meningoencephalitis returning from endemic areas.