Naegleria fowleri-associated primary amoebic meningoencephalitis in India: A systematic review and individual patient-level analysis of reported cases

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.