Pathological aspects of an amebiasis outbreak in captive testudines.

Abstract

Amebiasis is a parasitic disease primarily associated with amoeboid protozoa of the genus Entamoeba; however, comparable infections may also be caused by other genera in different hosts. In reptiles, it is mainly attributed to Entamoeba invadens, which can be fatal in several species. This report describes an outbreak of amebiasis in two species of testudines, red-footed tortoises (Chelonoidis carbonarius) and black-bellied sliders (Trachemys dorbigni), from a wildlife screening and rehabilitation centre in Minas Gerais, Brazil. The facility housed around 130 testudines, and between 2022 and 2024, 79 animals died, of which 21 were diagnosed with amebiasis based on post-mortem examination. Clinical signs were non-specific, including anorexia, lethargy, reluctance to move and sudden death. Histological lesions were most frequent in the liver (17/21), duodenum (10/21) and colon (4/21), but were also present in the coelomic wall (4/21), lungs (2/21) and spleen (1/21). Lesions were characterized by necrosis, fibrin deposition and inflammatory infiltrates of lymphocytes and histiocytes, associated with numerous intralesional amoeboid protozoa. For diagnostic confirmation and species-level identification, polymerase chain reaction was performed on frozen tissues from six animals, targeting the amplification of a 109 bp fragment of the E. invadens 18S rRNA gene. Based on the pathological and molecular findings, along with protozoan species identification, a definitive diagnosis was established. Although amebiasis has been reported previously in reptiles, including red-footed tortoises, this is the first description in black-bellied sliders. This study highlights the importance of amebiasis as a cause of morbidity and mortality in captive testudines.