Beyond granulomatous amoebic encephalitis: changing epidemiology and an expanding spectrum of non-flagellated amoebic CNS infection in India

Abstract Purpose Granulomatous amoebic encephalitis (GAE) is the conventional label for central nervous system (CNS) infection caused principally by Acanthamoeba spp. and Balamuthia mandrillaris , but contemporary disease encompasses meningitic, focal, vascular, brainstem, and spinal phenotypes that extend beyond the classical description. This narrative review examines the changing epidemiology, clinical spectrum, diagnosis, and management of non-flagellated amoebic CNS infection in India. Methods We narratively synthesised published Indian case reports, case series, molecular studies, surveillance investigations, and relevant environmental and epidemiological evidence on CNS infections caused by Acanthamoeba , Balamuthia , Vermamoeba , and Sappinia . Results Historically, disease in India was recognised mainly through sporadic reports of Acanthamoeba GAE, with occasional confirmed Balamuthia infection. More recent reports from several regions, particularly Karnataka and West Bengal, together with systematic surveillance in Kerala, suggest a substantial expansion in recognised disease. Contemporary Indian experience increasingly includes apparently immunocompetent patients and a broader neurological spectrum, including chronic meningitis mimicking CNS tuberculosis, focal abscess, parkinsonism, myelopathy, and rhombencephalomyelitis; relapse after apparent recovery has also been documented. Water-related exposures and use of nonchlorinated domestic water have emerged as potentially important epidemiological associations. Molecular studies confirm that Acanthamoeba is the dominant contemporary organism, whereas Balamuthia remains rare; reported Vermamoeba infections warrant cautious interpretation, and no Indian Sappinia CNS infection was identified. Treatment remains empirical, multidrug, and poorly standardised. Conclusion The recent Indian experience probably reflects substantial diagnostic discovery superimposed on a possible true increase in environmentally acquired Acanthamoeba CNS infection. Organism-specific surveillance, improved molecular diagnosis, and prospective treatment data are needed to define the true burden, transmission pathways, and optimal management of these infections.