16 - Acanthamoeba spp.

Abstract

This chapter discusses Acanthamoeba spp., basic microbiology, origin and taxonomy, metabolism and physiology, clinical features, pathogenicity and virulence, treatment, survival in the environment, methods of detection, epidemiology of waterborne outbreaks, and finally, risk assessment. Several species of the free-living amoebae Acanthamoeba are commonly found in soil and water. They have been implicated in human infections and disease, including Acanthamoeba culbertsoni, Acanthamoeba polyphaga, Acanthamoeba castellanii, Acanthamoeba astronyxis, Acanthamoeba hatchetti, Acanthamoeba griffini, Acanthamoeba lugdenensis and Acanthamoeba rhysodes. The types of Acanthamoeba mainly associated with human disease are A. culbertsoni, which causes the rare but fatal granulomatous amoebic encephalitis (GAE), and A. polyphaga and A. castellanii, which are more usually associated with keratitis.There appears to be no risk to healthy individuals from the ingestion of Acanthamoeba. However, it is recommended that immunocompromised persons boil drinking water before consumption. The transmission of keratitis caused by Acanthamoeba is largely driven by risky behaviour in contact lens wearers. Recognized risk factors for keratitis are poor hygiene practices such as washing and/or storing contact lenses in non-sterile solutions or tap water and inadequate disinfection of lenses.