Chapter Fourteen - Acanthamoeba

Abstract

This chapter discusses Acanthamoeba spp., basic microbiology, history, life cycle and taxonomy, clinical features, pathogenicity, virulence and causation, treatment, methods of detection, survival in water and the environment, a critical review of the epidemiology 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, Acanthamoeba polyphaga and Acanthamoeba rhysodes. The types of Acanthamoeba mainly associated with human disease are A. culbertsoni, which causes a rare but fatal granulomatous amoebic encephalitis (GAE), and A. polyphaga and A. castellanii, which are more usually associated with ocular infection and 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. Having a history of trauma to the cornea is a risk factor for Acanthamoeba keratitis, but the leading risk factor is contact lens wear, increased by poor hygiene practices such as washing and/or storing contact lenses in non-sterile solutions or tap water and inadequate disinfection of lenses.