The causative agent of hemorrhagic disease in giant devil catfish (Bagarius yarrelli) in cage culture at Tuyen Quang province and proposing preventive and treatment measures

Abstract

Giant devil catfish (Bagarius yarrelli) is one of the five precious fish species which bring high economic values and are popularly cultured in cage in the northern mountainous provinces as well. Tuyen Quang province has the advantages of water sources for aquaculture breed availability, technology, and farming techniques, but has limited information of pathogens in giant devil catfish. Therefore, this study aims to determine common pathogens in giant devil catfish during cage culture in this province. Bacterial culture, isolation, identification, and infection experiment were applied for this study. The results showed that Aeromonas hydrophila was the causative agent of hemorrhagic disease in giant devil catfish with such clinical signs as red spots, ulcers, hemorrhage in skin and liver, empty stomach, and abdomen containing fluids. A. hydrophila had high virulence, causing mortality upto 100% in 3 days at the dose of 10⁴ -10⁶ cfu/ml. At the concentration of 103 cfu/ml, A. hydrophila can cause the death of experimental fish with signs of abdominal ulcer, liver and kidney hemorrhage. The mortality increases gradually over time from 47.6% at day 2 to 90.5% at day 4 and reached 100% at day 5 post challenge.