Aeromonas spp. challenge model development and immune response characterization in largemouth bass (Micropterus nigricans)

Abstract

Largemouth bass, Micropterus nigricans, is a popular sportfish in the United States and commonly sought after recreationally in freshwater systems. The culture of LMB supports and maintains large economic and traditional stocking practices in the United States. Recently, the use of intensive aquaculture has led LMB to become a major food fish in areas outside of the United States. Global production of LMB peaked at 0.458 million tons in 2017, predominantly in China. As the need for LMB increases, the production and handling of these organisms must increase. The influx of LMB density in intensive aquaculture systems generates various bacterial and viral diseases, leading to economic losses and production inefficiencies. One specific bacterial pathogen responsible for disease outbreaks is Aeromonas spp., which are abundant and commonly found in freshwater ecosystems and aquaculture systems. Aeromonas spp. are responsible for motile aeromonad septicemia (MAS), which is identified by skin lesions, exophthalmia, and abdominal swelling. To effectively assess the impacts of MAS on largemouth bass, a standardized immersion-based challenge model was developed for Aeromonas spp. and was then applied to a long-term study of growth performance and disease susceptibility. Challenge results from these studies show the viability of an immersion-based challenge model, and the relationship between disease susceptibility and age/size of the largemouth bass. These disease and growth assessments will allow for better rearing and disease management practices for commercial largemouth bass production, as well as the future production of therapeutants and new disease management strategies.