Journal Article

Implications of ammonia stress for the pathogenicity of Shewanella spp. in Oreochromis niloticus: effects on hematological, biochemical, immunological, and histopathological parameters

Abdel-Basset, Nehal A., Ibrahim, Rowida E., Metwally, Mohamed M. M., Reda, Rasha M., El-Murr, Abdelhakeem

2024

Overview

Environmental stressors (such as ammonia) in aquaculture could increase the risk of pathogenicity, posing a more severe threat to farmed fish. The aim of this study was to investigate the effects of ammonia stress on the pathogenicity of Shewanella spp. in Oreochromis niloticus . First, a 96-hour static test was used to determine the median lethal concentration (LC 50 ) of unionized ammonia to Nile tilapia. After 96 h of exposure, the Un-ionized ammonia (UIA) LC 50 was estimated to be 4.26 mg/L. Second, an experiment was conducted to test the effect of unionized ammonia stress on the pathogenicity of Shewanella spp. in O. niloticus for 30 days. A study involved 180 fish divided into six groups, with the first group serving as a control. The second group (AMN1/10) and the third group (AMN1/20) were not challenged and were exposed to 1/10 (0.42 mg/L) and 1/20 (0.21 mg/L) of the 96-hour LC 50 of UIA, respectively. Then 0.2 mL (0.14 × 10 5 ) of Shewanella spp. was intraperitoneally injected into the fourth (SH), fifth (SH + AMN1/10), and sixth (SH + AMN1/20) groups, which were subjected to 0, 1/10 (0.42 mg/L), and 1/20 (0.21 mg/L) of the 96-hour LC 50 of UIA, respectively. The survival rate, hematological indices, immunological parameters, and antioxidant activity of the fish significantly decreased when they were exposed to ammonia and Shewanella infection separately or together. Histopathological changes were also observed in the kidney and liver. Furthermore, both individual and combined exposures significantly altered renal and hepatic function, with notable increases in glucose and cortisol levels, as well as in the expression of proinflammatory cytokine genes ( TNF-α and IL-1ß ). However, the detrimental effects of co-exposure to ammonia stress and Shewanella infection were greater than those of separate exposures. As a result, we may say that increased ammonia concentrations enhance the infection of Shewanella spp. These findings could contribute to a better understanding of Shewanella infection in Nile tilapia.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Advancements in Veterinary Medicine and Aquaculture / Ammonia / Ammonia stress / Animals / antioxidant activity / Aquaculture / Bacteria / Bacterial infections / Cichlids / Cortisol / cytokines / Development and progression / Diseases / Drinking water / Epidemics / farmed fish / Fish Diseases - microbiology / Fish-culture / glucose / Gram-Negative Bacterial Infections - microbiology / Gram-Negative Bacterial Infections - veterinary / Health aspects / Hematology / histopathology / Immune system / Immunity / Infections / kidneys / lethal concentration 50 / Lethal Dose 50 / liver / liver function / Medicine / Medicine & Public Health / Mortality / Nile tilapia / Oreochromis niloticus / Pathogenicity / Pathogens / Physiological aspects / Proteins / Renal function / risk / Risk factors / Shewanella / Shewanella - drug effects / Shewanella - pathogenicity / Stress (Physiology) / Stress, Physiological - drug effects / survival rate / Sustainable development / Tilapia / Transgenics / Tumor necrosis factor-α / Veterinary Medicine/Veterinary Science / Zoology