Unusual Findings of Human-Associated Four-Nucleated Species in Captive Wild Animals.

Several species of amoebae in the genus forming four-nucleated mature cysts are pathogenic, but their identification is challenging due to a lack of distinctive morphological traits. Furthermore, host species cannot reliably be used as a criterion for identification. In this study, several isolates of four-nucleated cyst-forming species from animals at the Zoo Aquarium of Madrid are genetically identified. cysts were identified through microscopic analysis of faecal samples; none of the animals exhibited symptoms. DNA was extracted, and a fragment of the SSU-rRNA gene was PCR-amplified and sequenced to identify the species. was identified in mantled guerezas (), lar gibbons (), greater rheas () and giant anteaters (). was detected in mandrills () and chimpanzees (). was detected in mandrills; the analysis of sequences available in GenBank revealed that this species has also been detected in human samples. The identification of the species across diverse host species underscores the need for genetic confirmation to prevent misidentifications. These findings expand the known host range of these species and emphasize the importance of regular monitoring to minimize transmission risks, including potential cross-species transmission to/from humans.