Variation in cases per month of acanthamoeba, a waterborne pathogen

Introduction Since we began using the confocal microscope to identify and diagnose Acanthamoeba keratitis, we have detected an increased incidence of this pathogen and have now identified 138 cases since 1993 at our institution. The flood of the Iowa River in the summer of 1993 appears to be associated temporally with this increase in Acanthamoeba case presentation. Methods We evaluated the number of cases and their onset of symptoms per month for cases of Acanthamoeba keratitis diagnosed at our institution for the last four years. Results We have detected an association between the number of cases presented per month and the time of year such that summer and fall months appear to have a much higher incidence for the beginning of onset of symptoms compared with winter months. Summer and fall months (June through January) average 4. 2 cases per month whereas the months of late winter and spring (February through May) average 1. 62 cases per month. This difference was significant. Conclusions We hypothesize this difference in onset of symptoms is due to a change in the number of Acanthamoeba organism present in the water supply or activities associated with. This data supports our hypothesis that this is frequently a waterborne contaminant and that this parasite load is affected by changes in ambient temperature.