Acanthamoeba keratitis: The Persistence of Cases Following a Multistate Outbreak

Abstract

Purpose: To describe the trend of Acanthamoeba keratitis case reports following an outbreak and the recall of a multipurpose contact lens disinfection solution. Acanthamoeba keratitis is a serious eye infection caused by the free-living amoeba Acanthamoeba that primarily affects contact lens users.

Methods: A convenience sample of 13 ophthalmology centers and laboratories in the USA, provided annual numbers of Acanthamoeba keratitis cases diagnosed between 1999–2009 and monthly numbers of cases diagnosed between 2007–2009. Data on ophthalmic preparations of anti-Acanthamoeba therapies were collected from a national compounding pharmacy.

Results: Data from sentinel site ophthalmology centers and laboratories revealed that the yearly number of cases gradually increased from 22 in 1999 to 43 in 2003, with a marked increase beginning in 2004 (93 cases) that continued through 2007 (170 cases; p < 0.0001). The outbreak identified from these sentinel sites resulted in the recall of a contact lens disinfecting solution. There was a statistically significant (p ≤ 0.0001) decrease in monthly cases reported from 28 cases in June 2007 (following the recall) to seven cases in June 2008, followed by an increase (p = 0.0004) in reported cases thereafter; cases have remained higher than pre-outbreak levels. A similar trend was seen in prescriptions for Acanthamoeba keratitis chemotherapy. Cases were significantly more likely to be reported during summer than during other seasons.

Conclusion: The persistently elevated number of reported cases supports the need to understand the risk factors and environmental exposures associated with Acanthamoeba keratitis. Further prevention efforts are needed to reduce the number of cases occurring among contact lens wearers.

KEYWORDS::

• Acanthamoeba keratitis
• Surveillance
• Epidemiology
• Contacts lens
• Outbreak

ACKNOWLEDGEMENTS

Kirk R. Wilhelmus, MD, Alice Matoba, MD, Department of Ophthalmology and Cullen Eye Institute, Baylor College of Medicine; Miriana Pehar, Hospital Epidemiology and Infection Control, Johns Hopkins Hospital; Emily Luckman, MPH, Maryland Department of Health and Mental Hygiene; Francis S. Mah, Paul P. Thompson at the Charles T. Campbell Laboratory, University of Pittsburgh Medical Center; Marlene L. Durand, Massachusetts Eye and Ear Infirmary for providing data on AK cases and Govinda Visvesvara, Centers for Disease Control and Prevention for expert consultation on Acanthamoeba.

Declaration of interst: No authors are employed by corporations financially impacted by the results reported in this manuscript. Some authors are employed by the US Government and some authors receive funding from FDA and NEI. Some authors report consulting fees for Bausch and Lomb, BioTissue, Foresight, VisionCare, Inspire, Kimberly Clark, Alcon, Santen, Crofessionals; lecture fees for Alcon; and royalties from Roche Diagnostics. Detailed information is available on request.