Naegleria fowleri-associated primary amoebic meningoencephalitis in India: A systematic review and individual patient data meta-analysis.

Background

Primary amoebic meningoencephalitis (PAM), caused by Naegleria fowleri, is a rare but highly fatal infection of the central nervous system. Data on its epidemiology, diagnosis, and outcomes in India are limited.

Objectives

To systematically review published cases of PAM in India and summarize their epidemiology, clinical characteristics, diagnostic methods, treatment, and outcomes.

Methods

We conducted a systematic search of PubMed, Web of Science, and the Cochrane Library to identify studies reporting human cases of PAM due to N. fowleri in India. Individual patient-level data on demographics, exposure history, clinical features, diagnostic methods, treatment, and outcomes were extracted. Study quality was assessed using the Joanna Briggs Institute critical appraisal tool.

Results

Twenty-three studies reporting 24 patients from 1998 to 2025 were included. Most cases originated from Kerala (n=4), Karnataka (n=3), Uttar Pradesh (n=3), and Delhi (n=3). Freshwater exposure was documented in 15 (62.5%) patients, with environmental confirmation in two cases. Patients ranged in age from 13 days to 85 years, with a male predominance (n=20). Fever (79.2%), headache (58.3%), and seizures (41.6%) were the most common presenting features. Cerebrospinal fluid wet-mount microscopy detected trophozoites in 23 (95.8%) cases, whereas PCR confirmation was reported in only 2 cases. Amphotericin B was administered to 22 (91.6%) patients, while miltefosine was used in one case. Among evaluable patients (n=22), mortality was 63.6%.

Conclusions

PAM remains a rare but devastating infection with high mortality and is probably under-recognized in India. Early clinical suspicion, routine cerebrospinal fluid wet-mount examination, wider availability of molecular diagnostics, and strengthened environmental surveillance are essential for improving timely diagnosis and patient outcomes.