Parasitic fauna and histopathology of farmed freshwater ornamental fish in Brazil

Abstract

Ornamental fish farming represents a consolidated market over the world. However, confinement is a factor that favors the occurrence of diseases. This study aimed to report the parasitic fauna of ornamental fish from three facilities, as well as to observe the histological pathogenesis caused by the parasites. Between May 2015 and February 2016, a total of 781 ornamental fishes were used for parasitological and histopathological analysis. Water quality was measured in fishponds from each facility. Ciliate protozoans Ichthyophthirius multifiliis; Trichodina sp.; the monogeneans Dactylogyrus extensus, D. minutus and Diaphorocleidus kabatai; metacercariae of the digeneans; the cestode Bothriocephalus acheilognathi; the nematode Rhabdochona sp.; and the branchiuran Argulus japonicus were found in the examined fish. The greatest prevalence and mean intensity was observed in the gills of Gymnocorymbus ternetzi parasitized by D. kabatai, followed by the protozoan parasite I. multifiliis on the body surface of Xiphophorus maculatus. Histopathological analysis showed epithelial interlamellar hyperplasia of the secondary lamellae, partial fusion of the secondary lamellae, telangiectasia, justalamellar edema and eosinophilic inflammatory infiltrate. The intestine of cestode parasitized fish showed necrosis in the submucosa, intestinal obstruction and lymphoeosinophilic inflammatory infiltrate. It is important to know the parasitic fauna of farmed fish and the pathogenesis caused by the parasites in order to ensure fish production and the health of the hosts. Statement of relevanceOrnamental fish production as a consolidate activity around the world faces problems of parasite infection leading to fish mortality and economic losses. To ensure farming production, it is important to monitor the status of fish health. Parasitic fauna and histopathological analysis are used as important tools for the diagnosis of tissue lesions.