Nodular gill disease in Northeastern Italy: An investigation on the prevalence of the disease and the risks of introduction in rainbow trout farms

Abstract

Nodular Gill Disease (NGD) is an emerging pathogenic condition that causes gill damage and mainly affects farmed freshwater fish, rainbow trout (Oncorhynchus mykiss) in particular, and this inevitably generates noticeable economic losses for the industry. The present study aimed to assess the prevalence of NGD in the Autonomous Province of Trento, a highly productive area located in Northeastern Italy, traditionally suited to rainbow trout production, and to identify possible risk factors for the introduction of this disease in trout farms. The necessary data were obtained through a questionnaire and the collection of fish samples. According to the data analysis, 42% of the investigated farms tested positive for NGD. The two possible risk factors identified for its introduction in farms are the presence of other diseases in the same farm (OR = 17.5; 95% CI = 2.7; 111.5) and having farms located 5 km upstream (OR = 24.8; 95% CI = 2.9; 211.1). These results highlight (i) a possible impairment of the immune system caused by other diseases as a predisposing factor to the manifestation of the pathology and (ii) the role of water in spreading pathogens.

Identification of new amoebae strains in rainbow trout (Oncorhynchus mykiss, Walbaum) farms affected by nodular gill disease (NGD) in Northeastern Italy

“…Given the high prevalence of rainbow trout farming systems in the Northeastern region of Italy and the high prevalence reported in the last decade of amoebic elements associated with hyperplastic gill disease (Cocco et al, 2023), this area was selected as a starting point for a rigorous evaluation of the disease.…”

“…Gills have a stereotypical response to many noxious stimuli, and determining the initial stimulating injury can be challenging. Moreover, many factors other than pathogens contribute to establishing a disease (Cocco et al, 2023), including water temperature, population density, environmental contaminant, stress and fish development stage (Adams & Nowak, 2001;Zilberg & Munday, 2000).…”