Abstract Within each ecosystem, organisms and populations maintain a complex set of relationships. These interactions can determine the distribution area of a species and play an essential role in its evolution. Parasites are ubiquitous components of nature and have a high influence on various aspects of the biology and ecology of organisms, affecting the populations of their hosts and, therefore, their communities and ecosystems. Free-living amoebae are unicellular organisms that can be found in water, soil or air. Some species are of great importance in human health. In Hydra, there are several reports of Hydramoeba hydroxena infections. In this work we present a double parasitosis: two concatenated infectious periods in the host polyp of Hydra vulgaris and Hydra vulgaris pedunculata for three freshwater bodies in the province of Buenos Aires, Argentina. Hydramoeba sp. and Acanthoamoeba sp. unchain a series of anatomical lesions that in all cases cause the death of the polyps due to total disintegration. This finding becomes important at a sanitary level due to the appearance of Acanthoamoeba sp. in waters associated with human recreational activities; For the Hydra genus, the importance lies at an ecological and evolutionary level, considering the possible impact on its natural populations. ecosystem relationships evolution therefore ecosystems Freeliving Free living water air health infections parasitosis Aires Argentina sp disintegration activities genus

Free-living amoeba (FLA) group includes the potentially pathogenic genera Acanthamoeba, Naegleria, Balamuthia, Sappinia, and Vermamoeba, causative agents of human infections (encephalitis, keratitis, and disseminated diseases). In Brazil, the first report on pathogenic FLA was published in the 70s and showed meningoencephalitis caused by Naegleria spp. FLA studies are emerging, but no literature review is available to investigate this trend in Brazil critically. Thus, the present work aims to integrate and discuss these data. Scopus, PubMed, and Web of Science were searched, retrieving studies from 1974 to 2020. The screening process resulted in 178 papers, which were clustered into core and auxiliary classes and sorted into five categories: wet-bench studies, dry-bench studies, clinical reports, environmental identifications, and literature reviews. The papers dating from the last ten years account for 75% (134/178) of the total publications, indicating the FLA topic has gained Brazilian interest. Moreover, 81% (144/178) address Acanthamoeba-related matter, revealing this genus as the most prevalent in all categories. Brazil’s Southeast, South, and Midwest geographic regions accounted for 96% (171/178) of the publications studied in the present work. To the best of our knowledge, this review is the pioneer in summarising the FLA research history in Brazil.

BACKGROUND Acanthamoeba is the genus of free-living amoebae that is most frequently isolated in nature. To date, 20 Acanthamoeba genotypes have been described. Genotype T4 is responsible for approximately 90% of encephalitis and keratitis cases. Due to the ubiquitous presence of amoebae, isolation from environmental sources is not uncommon; to determine the clinical importance of an isolation, it is necessary to have evidence of the pathogenic potential of amoebae. OBJECTIVE The aim of this study was to physiologically characterise 8 Acanthamoeba T4 isolates obtained from dental units and emergency combination showers and to determine their pathogenic potential by employing different laboratory techniques. METHODS Eight axenic cultures of Acanthamoeba genotype T4 were used in pathogenic potential assays. Osmotolerance, thermotolerance, determination and characterisation of extracellular proteases and evaluation of cytopathic effects in MDCK cells were performed. FINDINGS All of the isolates were osmotolerant, thermotolerant and had serine proteases from 44-122 kDa. Two isolates had cytopathic effects on the MDCK cell monolayer. MAIN CONCLUSION The presence of Acanthamoeba T4 with pathogenic potential in areas such as those tested in this study reaffirms the need for adequate cleaning and maintenance protocols to reduce the possibility of infection with free-living amoebae.