Notes from the Field: Acanthamoeba Keratitis Cases — Iowa, 2002–2017

Weekly / May 17, 2019 / 68(19);448–449

Brittni A. Scruggs, MD, PhD1; Tyler S. Quist, MD1; Jorge L. Salinas, MD2; Mark A. Greiner, MD1,3 (View author affiliations)

Acanthamoeba is a ubiquitous protozoan that feeds on bacteria and yeast. Because of its ability to encyst in extreme environmental conditions, the organism is difficult to kill. Contact lens wearers exposed to any water source are at highest risk for developing Acanthamoeba keratitis (AK), a severe corneal infection that can result in painful blindness. Variable findings when patients seek treatment contribute to the underdiagnosis of AK, and the amoeba’s resistance to killing makes AK a challenging infection to treat for ophthalmologists. The incidence of Acanthamoeba keratitis in the United States is estimated to be one to two new cases per 1 million contact lens wearers annually (1); approximately 16.7% of U.S. adults wear contact lenses (2). Among the estimated 2.42 million Iowa residents aged ≥18 years, including an expected 404,267 adult contact lens wearers (16.7%), 0.4–0.8 new AK cases per year would be expected in Iowa. However, the University of Iowa Hospitals & Clinics (UIHC), the only tertiary care center in Iowa, diagnosed 15 new AK cases in 2015, 14 of which were adults. Because of this apparent excess in occurrent cases, a retrospective investigation was performed to ascertain AK cases evaluated at UIHC during a 16-year period.