Human infections caused by free-living amoebae

Introduction. Among free-living amoebae that are widely distributed in nature only four genera/species are known as agents of human infections: Acanthamoeba spp., Naegleriafowleri, Balamuthia mandrillaris and Sappiniapedata. These amoebae are not well adapted to parasitism, and could exist in the human environment without the need for a host. Infections due to these amoebae, despite low morbidity, are characterized by relatively high mortality rate and pose serious clinical problems. Objectve. This review study presents and summarizes current knowledge about infections due to pathogenic and opportunistic free-living amoebae focused on epidemiology, clinical manifestations, diagnosis and treatment based on global literature. State of knowledge. All four genera have been recognized as etiologic factors of fatal central nervous system infections and other serious diseases in humans. N. fowleri causes an acute fulminating meningoencephalitis in children and young adults. Acanthamoeba spp. and B. mandrillaris are opportunistic pathogens causing granulomatous amoebic encephalitis and disseminated or localized infections which could affect the skin, sinuses, lungs, adrenals and/or bones. Acanthamoeba spp. is also the main agent of acute eye infection -Acanthamoeba keratitis, mostly in contact lens wearers. However, there is only one recognized case of encephalitis caused by S. pedata. Conclusions. Amoebic diseases are difficult to diagnose which leads to delayed treatment, and result in a high mortality rate. Considering those issues, there is an urgent need to draw more attention to this type of diseases.