Molecular identification, phylogenetic analysis and histopathological study of pathogenic free-living amoebae isolated from discus fish (Symphysodon aequifasciatus) in Iran: 2020-2022.

Free-living amoebae (FLA) are capable of inhabiting diverse reservoirs independently, without relying on a host organism, hence their designation as "free-living". The majority of amoebae that infect freshwater or marine fish are amphizoic, or free-living forms that may colonize fish under particular circumstances. Symphysodon aequifasciatus, commonly referred to as the discus, is widely recognized as a popular ornamental fish species. The primary objective of the present study was to determine the presence of pathogenic free-living amoebae (FLA) in samples of discus fish. Fish exhibiting clinical signs, sourced from various fish farms, were transferred to the ornamental fish clinic. The skin, gills, and intestinal mucosa of the fish were collected and subjected to culturing on plates containing a 1% non-nutrient agar medium. The detection of FLA was conducted through morphological, histopathological and molecular methods. The construction of the phylogenetic tree for Acanthamoeba genotypes was achieved using the maximum likelihood approach. The molecular sequence analysis revealed that all cultures that tested positive for FLA were T4 genotype of Acanthamoeba and Acanthamoeba sp. The examination of gill samples using histopathological methods demonstrated the presence of lamellar epithelial hyperplasia, significant fusion of secondary lamellae, and infiltration of inflammatory cells. A multitude of cysts, varying in shape from circular to elliptical, were observed within the gills. The occurrence of interlamellar vesicles and amoeboid organisms could be observed within the epithelial tissue of the gills. In the current study, presence of the Acanthamoeba T4 genotype on the skin and gills of discus fish exhibiting signs of illness in freshwater ornamental fish farms was identified. This observation suggests the potential of a transmission of amoebic infection from ornamental fish to humans, thereby highlighting the need for further investigation into this infection among ornamental fish maintained as pets, as well as individuals who interact with them and their environment.

First Report of Joyeuxiella spp. Infection in Eurasian Lynx and Its Histopathology Study from Iran: A Case Report.

According to the last information of IUCN Red List, Eurasian lynx has been endangered since 2010. The population of this animal is heavily affected by infectious parasites. Two adult Eurasian lynx (one male and one female) were illegally hunted and found dead in Parvar National Park, Semnan Province, Iran. After the autopsy, the tissue and parasite samples were collected from gastrointestinal tract and transferred to 70% alcohol. Samples were recovered and identified as Joyeuxiella spp. Sonsino, 1889. Tissue samples were taken from the place of sticking of parasites on the intestinal wall, for histopathological examination, and were transferred to 10% buffered formalin. Following routine processes and H&E staining, the slides were examined microscopically. Main histopathological observations were epithelial hyperplasia and destruction, inflammatory cell infiltration in mucosa and submucosa of jejunum. To the best of the author's knowledge, this is the first report and histopathological study of Joyeuxiella spp. in the world in Eurasian lynx.