Ventricular hypoplasia in farmed rainbow trout

Objective: Malformations in skeletal and soft tissues have been known to occur in feral and farmed fish for a very long time. Various factors have been known to be the causative agent including biological, nutritional, hereditary, chemical, physical and environmental factors. These include swimbladder anomaly, polycystic liver, situs in versus of the heart, hypoplasia/aplasia of septum transversum and several other conditions that are hitherto undescribed, e.g., reduced number of pyloric caecae, situs inversus of the liver and cranial and spinal disorders.parr and presmolts with clinical signs of severe cardiac failure were reported by fish farmers and fish health veterinarians in several smolts. Method & Materials: A total of 200 fish from 4 smolt farms in different regions in Tabriz were collected. Healthy and diseased individuals were sampled individually, based on clinical appearance from Farm A and Sampling No. 1 from Farm B. Healthy fish for reference were sampled from 2 unaffected farms (Farms C and D) and used as controls, while a random sampling after crowding of the fish was done in Sampling No. 2 in Farm B. All sampled fish were killed with an overdose of Benzocaine and examined immediately. In 72 fish (38 diseased and 34 healthy controls), the liver and digestive tract were examined. Results & Conclusion: Clinical findings: Affected fish were typically darker than normal fish and exhibited moderate to severe distension of the abdomen with bilateral exophthalmia. These fish were less active than normal fish, stayed on the bottom of the tanks and had reduced stamina when chased with the fish net. In Farms A and B, the weight of fish with ventricular hypoplasia was significantly lower than that of the healthy individuals, and they also had a higher condition factor. Gross pathology: Characteristic external findings included dark coloration, exophthalmia and a swollen abdomen. In addition, there was water logging of the scale pockets in some fish, reflected in raised scales, a matt surface and water squirting from the surface when the skin was pressed. Five fish (4.76%) with no septum transversum and 5 fish (4.76%) with hypoplastic ventricle were found in the second sample from Farm B. Histopathology: Histology of affected hearts revealed that the shape of a cross section of the ventricle changed from the normal triangular shape, to a more rounded appearance. Hearts of salmonids may undergo morphological changes during the life cycle of the fish and may also show considerable variation depending on gender and habitat.

کلیدواژه ها:

Rainbow trout ، Ventricular hypoplasia ، Cardiac malformation