Piscine lactococcosis is a critical bacterial disease impacting farmed fish, predominantly caused by species within the Lactococcus genus, including Lactococcus garvieae, Lactococcus petauri , and Lactococcus formosensis. Timely and accurate diagnosis is essential for effective outbreak management and mitigation of economic losses in aquaculture. While conventional diagnostic methods provide reliable results, they often necessitate specialized laboratory infrastructure and extended processing times, which limits their practicality in field conditions.
To overcome these limitations, we have developed a novel point-of-care (POC) diagnostic assay leveraging Recombinase Aided Amplification (RAA) technology combined with a lateral flow dipstick (LFD) detection system, enabling rapid and specific identification of piscine lactococcosis causative agents. Three species-specific RAA assays were designed, each targeting distinct genetic markers of L. garvieae, L. petauri , and L. formosensis. These assays exhibited high specificity, with no cross-reactivity detected among target species or other bacterial strains tested. Sensitivity analysis demonstrated a limit of detection between 10 and 20 genome copies, underscoring the assay’s capability to detect low bacterial loads, which is critical for early diagnosis. Preliminary validation using field samples from infected fish yielded promising results, with each assay accurately detecting its corresponding pathogen without cross-detection. Ongoing efforts aim to broaden field validation across diverse geographical locations and aquaculture systems to further confirm assay robustness and reliability. Additionally, assay optimization is underway to enhance usability for non-specialist personnel, including simplified sample preparation and streamlined workflow.
In conclusion, the developed RAA-LFD diagnostic assays represent a rapid, sensitive, and specific POC solution for detecting Lactococcus species responsible for piscine lactococcosis. This advancement has the potential to significantly improve disease management in aquaculture by enabling decentralized testing, reducing dependence on centralized laboratories, and supporting sustainable fish production practices.