Environmental-Nitrite-Enhanced Cyprinid Herpesvirus 2 Infection in Crucian Carp

Area of Science:

• Aquatic toxicology
• Fish immunology
• Virology

Background:

• Water quality deterioration increases disease risk in aquatic organisms.
• The specific mechanisms linking environmental stressors to viral infections are not fully understood.
• Cyprinid herpesvirus 2 (CyHV-2) poses a threat to fish health.

Purpose of the Study:

• To investigate the impact of varying nitrite stress levels on CyHV-2 infection dynamics in crucian carp (Carassius auratus gibelio).
• To elucidate the physiological and immunological responses of fish to combined nitrite stress and viral infection.

Main Methods:

• Experimental setup included a control group and CyHV-2 infected groups exposed to 0, 5, and 10 mg/L nitrite.
• Assessed survival rates, viral loads, oxidative stress markers (MDA, GPx, SOD, CAT), hepatic cytokine expression (TNF-α, IL-1β, IFN-γ, IL-10), and kidney immune gene expression (tlr5, nf-κb, iκκβ, il-1β, il-8, ifn-γ).

Main Results:

• Nitrite exposure reduced survival and viral loads in a dose-dependent manner.
• Nitrite stress induced oxidative damage, altering antioxidant enzyme activities.
• Impaired hepatic cytokine regulation and prolonged kidney NF-κB signaling were observed, with specific gene expression changes.
• Combined stress and infection exacerbated oxidative damage and maladaptive immune responses.

Conclusions:

• Nitrite stress significantly impacts CyHV-2 infection in crucian carp.
• The study reveals complex interactions between environmental stress, oxidative damage, and immune system dysregulation.
• Findings highlight the detrimental effects of poor water quality on fish health and disease susceptibility.