354 - The Epidemiology and Clinical Features of Acanthamoeba Disease in the United States, 1956–2018

Background: Acanthamoeba is a free-living ameba found worldwide in soil and water that can cause severe illness. Transmission is thought to be through the skin, eyes, or lungs; Acanthamoeba can cause disseminated infection (Acanthamoeba disease) in addition to the more widely recognized Acanthamoeba keratitis. Infections however are rare, and only case reports or small case series have been published. We review Acanthamoeba disease cases from the Centers for Disease Control and Prevention (CDC) free-living ameba registry to characterize the disease in the United States.

Methods: CDC maintains a free-living ameba (FLA) registry of laboratory-confirmed Acanthamoeba cases (excluding keratitis) sourced from published case reports, CDC case report forms, and CDC laboratory results. SAS© version 9.4 software was used to calculate descriptive statistics and frequencies.

Results: We identified 163 cases of Acanthamoeba disease between 1956 and 2018. Of cases with documented outcome, 85% were fatal (105/124). Most (88%) cases were in patients who were immunocompromised (136/155): 66 people living with HIV (of whom 49 were classified as having AIDS); 33 recipients of organ transplantation; 30 people diagnosed with malignancy. The most common manifestation of disease was encephalitis (49%). Other clinical presentations included cutaneous lesions (20%) and rhinosinusitis (6%); 40 cases involved multiple organ systems. Median patient age was 42 years (range 0–83 years). Males accounted for 71% (114/160) of cases. California (29) and Texas (14) had the most case reports; 30 other states reported cases. The source of exposure was unknown in most cases (75%); soil and water were documented in 14 and 17 cases, respectively.

Conclusion: Acanthamoeba disease in the United States is primarily characterized by encephalitis and cutaneous lesions that affect predominately immunocompromised individuals. Acanthamoeba as a cause of encephalitis in immunocompromised patients should be considered by clinicians, which may lead to earlier diagnosis and treatment.