From the basics to emerging diagnostic technologies: What is on the horizon for tilapia disease diagnostics?

Abstract

Tilapia is an affordable protein source farmed in over 140 countries with the majority of production in low‐ and middle‐income countries. Intensification of tilapia farming has exacerbated losses caused by emerging and re‐emerging infectious diseases. Disease diagnostics play a crucial role in biosecurity and health management to mitigate disease loss and improve animal welfare in aquaculture. Three continuous levels of diagnostics (I, II and III) for aquatic species have been proposed by Food and Agriculture Organization of the United Nations (FAO) and the Network of Aquaculture Centers in Asia and the Pacific (NACA) to promote the integration of basic and advanced methods to achieve accurate and meaningful interpretation of diagnostic results. However, the recent proliferation of cutting‐edge molecular methods applied in the diagnosis of diseases of aquacultured animals has shifted the focus of researchers and users away from basic approaches and toward molecular diagnostics, despite the fact that many diseases can be rapidly diagnosed using inexpensive, simple microscopic examination and that most emerging diseases in aquaculture were discovered by histopathology. This review, therefore, revisits and highlights the importance of the three levels of diagnostics for diseases of tilapia, particularly the frequently overlooked basic procedures (e.g., case history records, gross pathology, presumptive diagnostic methods and histopathology). The review also covers current and emerging molecular diagnostic technologies for tilapia pathogens including polymerase chain reaction methods (conventional, quantitative, digital), isothermal amplification methods Loop‐mediated Isothermal Amplification (LAMP), recombinase polymerase amplification (RPA), clustered regularly interspaced short palindromic repeats (CRISPR)‐based detection, lateral flow immunoassays, as well as discussing what is on the horizon for tilapia disease diagnostics (next generation sequencing, artificial intelligence, environmental Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA) and point‐of‐care testing) providing a future vision for transferring these technologies to farmers and stakeholders for a sustainable aquatic food system transformation.

Improving the diagnosis of Streptococcus iniae using a novel probe‐based qPCR assay combined with an enrichment step

“…This study applied the three-level diagnostic approach outlined by FAO/NACA (2001) (Dong et al, 2023). The diagnosis procedures in this study were as follows.…”

“…The diagnosis of a disease involves collaborative knowledge and data for accurate and relevant diagnostic results. Food and Agriculture Organization of the United Nations and Network of Aquaculture Centres in Asia‐Pacific (2001) (FAO/NACA) have recommended three continuous levels of diagnostics (I, II and III) for aquatic animals (Dong et al, 2023; FAO/NACA, 2001). Level I involves gathering information from the field and appropriate sample collection and preservation for further analysis in the laboratory.…”

“…While various molecular techniques are available for detecting S. iniae , a probe‐based quantitative PCR (qPCR) method for this pathogen has not yet been developed. Given the advantages of probe‐based qPCR over dye‐based qPCR in terms of minimal risk of generating false positives or non‐specific amplification, as well as its superior quantification nature compared with other molecular methods (Dong et al, 2023; Holland et al, 1991; Sigma Aldrich, 2008), our primary goal in the present study is to develop a probe‐based qPCR for the detection of S. iniae .…”

“…In addition, an enrichment step was included to enhance the detection sensitivity. During the clinical sample collection and investigation, we also incorporated the three disease diagnosis levels recommended by FAO/NACA (2001) (Dong et al, 2023) in this study.…”

Emerging technologies revolutionising disease diagnosis and monitoring in aquatic animal health

“…36 Research on refining these tools is underway to achieve the standards set by the regulatory bodies. 33,108…”