A survey to detect viral pathogens in wild-caught ornamental fish from ornamental fish wholesale facilities in the Peruvian Amazon

Peruvian ornamental fish industry is based on the trade of wild-caught Amazonian species, which are exported to several countries. Throughout the ornamental fish value chain, fish are exposed to different stressors, which enhance their susceptibility to pathogens. Major emerging viral diseases in ornamental fish may result in trade restrictions. Therefore, it is important for authorities to monitor the health status of ornamental fish populations. The aim of this study was to detect the presence of the genera Megalocytivirus and Ranavirus in five ornamental fish species from the Peruvian Amazon. A total of 600 wild-caught ornamental fish of five species were collected from ornamental fish wholesale facilities in the city of Iquitos, Peru, between June and September 2022. The samples included the species Hyphessobrycon erythrostigma , Corydoras splendens , Carnegiella strigata , Pterophylum scalare and Ancistrus temminckii and were analyzed by quantitative PCR (qPCR) and histopathology. The qPCR results did not detect Megalocytivirus and Ranavirus. In addition, histopathology revealed the presence of monogenoids and Piscinoodinium sp. in the gills and metacercarial cysts in the liver. Furthermore, histopathological examination revealed an unusual finding of Ichthyophthirius sp. in the esophagus of A. temminckii . The results showed that Megalocytivirus and Ranavirus were not detected during the sampling periods in at least five wild-caught ornamental fish species from the Peruvian Amazon and there are no histopathological lesions related to Megalocytivirus-infected fish. Finally, we advise that additional monitoring is necessary to detect the occurrence of the World Organization for Animal Health (WOAH) listed diseases in ornamental fish and develop strategies that ensure surveillance plans to consider the wide variety of Amazonian fish species in the ornamental fish trade, as well as the presence of disease-susceptible ornamental fish species.