Histopathological lesions of gill, liver and kidney of rainbow trout (Oncorhynchus mykiss) in some farms in Dohezar region of Mazandaran Province

Document Type : Original Article

Authors

1 Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran.

2 Iranian Fisheries Sciences Research Institute, Agricultural Research, Education and Extension Organization, Tehran, Iran.

3 Inland Waters Aquatics Resources Research Center, Iranian Fisheries Sciences Research Institute, Agricultural Research, Education and Extension Organization, Gorgan, Iran

4 Inland Waters Aquatics Resources Research Center, Iranian Fisheries Sciences Research Institute, Agricultural Research, Education and Extension Organization, Gorgan, Iran.

5 Department of Sciences and Technologies, University of Sannio, Benevento, Italy.

Abstract

Due to the lack of information on the health status of farmed fish and the number of trout farms in the north of the country, the health of rainbow trout was monitored in three farms in Mazandaran province with the help of histological studies. Sampling was performed in three weight groups and 10 fish for each group. The first group of fish weighing below 100 g, the second group of fish weighing 300-700 g, and the third group of fish weighing higher than 1.5 kg. After sampling, the gills, livers, and kidneys were removed and the tissue samples of each fish were fixed in a separate falcon tube containing 10% buffered formalin. Tissue sections were prepared using a standard protocol and examined by light microscopy after staining using eosin-hematoxylin. Lamellar/filament hypertrophy and hyperplasia, curling lamellar, epithelial lifting/edema, aneurysm, branching filament are the most injuries in the sampled gills. Hepatocyte degeneration, Sinusoidal dilation, Haemorage/Congestion, Hepatocyte vacuolization, Pyknotic nuclear, Melanomacrophage aggregation, Hepatocyte hypertrophy and Exudate were reported with different intensities in the liver tissue. The kidney samples showed some lesions as; Bowman’s capsule dilation and Glumerol shrinkage, Haemorage/Congestion, Macrophage aggregation, and Degeneration. According to the results, it is suggested to improve the water quality, type, and amount of food in the studied farms. Additional assessments such as water and food quality and pathogens in the pools to be performed

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