Risk factors related to Streptococcosis disease of tilapia in freshwater aquaculture

Abstract

The risk factors related to the occurrence of Streptococcosis disease in cultured freshwater tilapia in Hai Duong, Bac Giang, An Giang, Vinh Long, and Dong Thap provinces, were determined based on results obtained by proactive monitoring approach, including observing and analysing water quality and disease occurrence in tilapia during the period 2012 to 2019. The results showed that NO₂-N>0.25 mg/l is the most risk related to Streptococcosis disease in tilapia with odds ratio OR=37.4, followed by temperature ≥30^oC (OR=16.5), H₂S>0.02 mg/l (OR=10), NH₃>1 mg/l (OR=8.2), the density of Streptococcus spp. ≥1000 cfu/ml (OR=6.9), and the lowest was pH>8.5 (OR=2.5). Chemical oxygen demand (COD)>10 mg/l, NH₄-N>1 mg/l are positively correlated, but not risk factors related to Streptococcosis in tilapia. Dissolved oxygen (DO), Aeromonas spp., and total aerobic bacteria density in cultured water were not correlated and associated with the appearance of Streptococcosis in tilapia.