Studies on Vibrio campbellii as a newly emerging pathogen affecting cultured seabream (Sparus aurata) in Egypt

Abstract

Aquaculture has become a crucial solution for addressing food scarcity worldwide, including Egypt. However, the intensification of aquaculture practices has led to water quality degradation and the emergence of new fish diseases, such as vibriosis. This study aimed to investigate the molecular typing, prevalence, pathogenicity, and environmental risk factors associated with Vibrio campbellii (V. campbellii) in cultured seabream. A total of 160 gilthead seabream, Sparus aurata (40 fish/season), along with 48 water samples (n = 12/season) were collected randomly and seasonally from private fish farms in the Suez Canal area over the course of a year for laboratory examinations. Clinical and postmortem inspections revealed characteristic signs and lesions similar to those observed in well-known vibrios infections. Bacteriological tests revealed the presence of V. campbellii strains in various internal organs. The isolated bacteria were identified morphologically, biochemically, and molecularly by targeting the 16S rRNA conserved gene. Histopathological examination was performed, providing insights into pathogen-induced tissue damage and septicemic disease progression. The prevalence of V. campbellii showed variable patterns across seasons, with higher proportions of cases in the summer. To examine the diagnostic performance of several water quality measures, the Receiver Operating Characteristic (ROC) curve analysis was performed. The results showed various levels of predictive performance for the outcome variable V. campbellii, with ammonia serving as a significant predictor for the variable of interest. The challenge results indicated a 100% survival rate in the controls, whereas the challenged group exhibited a mortality number of 6.00 ± 0.58, resulting in a survival rate of 70.00 ± 2.89%. The current study emphasizes how crucial it is to take into account seasonal parameters to comprehend the prevalence and seriousness of vibriosis in mariculture. The findings add to a better understanding of the impact of water quality on fish disease emergence and can benefit the creation of appropriate management measures to ensure aquaculture populations’ health and well-being.