First case of ichthyophonosis in farmed rainbow trout Oncorhynchus mykiss in Serbia.

Ichthyophonosis is a disease caused by the mesomycetozoean parasite Ichthyophonus hoferi that affects a variety of fish species, including rainbow trout Oncorhynchus mykiss Walbaum. This disease is characterized by granulomatous lesions and necrosis in various organs, which can have severe impacts on the health and welfare of the fish. Ichthyophonosis has been found in several parts of the world, including Europe, and is a significant concern in the aquaculture industry and for populations of wild marine fishes. The rainbow trout is a widely cultured salmonid species in many countries, including Serbia. Although the presence of I. hoferi in rainbow trout has been reported in several countries, it has never been documented in Serbia. In this article, we report the first case of ichthyophonosis in rainbow trout in Serbia.

Ichthyophonosis in Peruvian rainbow trout Oncorhynchus mykiss: identification of endemic areas using molecular and histopathological tools.

Ichthyophonus infection was first detected in Peruvian Oncorhynchus mykiss in 1986, but the occurrence of ichthyophonosis disease in the region is unknown. This study investigated the presence and distribution of Ichthyophonus sp. in Peruvian rainbow trout using traditional and DNA sequencing tools. Between 2007 and 2008, 205 rainbow trout from 13 hatcheries in the Mantaro river basin were examined for the presence of Ichthyophonus, and at that time only 3 farms were positive. This early study confirmed the presence of Ichthyophonus sp. in the Tranca Grande lagoon for the first time, at a prevalence of 50%. In 2012, examination of 240 trout from 24 fish farms in 2 Peruvian Departments found 9 infected farms. More recently, in 2018, Ichthyophonus sp. was found in Lake Titicaca, infecting a trout in the Ichu area (in the Department of Puno). Our molecular analysis of the infected trout showed that ichthyophonosis disease in the Peruvian trout was caused by Ichthyophonus sp. Clade C. The finding of this pathogen in Lake Titicaca should be an alert for nearby farms and entities dealing with fish of economic importance in the rivers of Peru.