Pathogenic free-living amoebic encephalitis in Japan

Area of Science:

• Neurology
• Infectious Diseases
• Microbiology

Background:

• Over 600 cases of pathogenic free-living amoeba encephalitis reported globally.
• Japan has reported 24 cases between 1976 and 2018, primarily Balamuthia mandrillaris.
• Diagnosis is challenging due to non-specific symptoms and reliance on autopsy.

Purpose of the Study:

• To highlight the diagnostic challenges of free-living amoebic encephalitis.
• To emphasize the need for including amoebic encephalitis in differential diagnoses.

Main Methods:

• Review of reported cases of amoebic encephalitis in Japan.
• Analysis of etiological agents and diagnostic timing.
• Consideration of environmental isolation of Balamuthia mandrillaris.

Main Results:

• Balamuthia mandrillaris was the most common cause in Japan (18/24 cases).
• Only 3 of 8 pre-mortem diagnosed cases were successfully treated.
• Most cases were diagnosed post-mortem, indicating diagnostic difficulties.

Conclusions:

• Encephalitis caused by pathogenic free-living amoebas presents diagnostic challenges.
• Balamuthia mandrillaris is a significant cause in Japan, with environmental isolates found.
• Consideration of amoebic encephalitis in the differential diagnosis of encephalitis is recommended.