Tilapia aquaculture is a major source of animal protein, with global production reaching over 6 million tonnes in 2020. The rapid growth of the tilapia sector has led to a number of emerging disease threats and subsequent production losses. Risk analysis can provide a targeted approach for improving biosecurity in the tilapia sector. The aim of this work was to describe the tilapia value chain and review the important infectious agents of tilapia that may affect the different points along the value chain; such points include input and service suppliers, producers (i.e., hatcheries, nurseries and grow‐out farms), and processors, traders and marketers. We then describe how risk analysis can be used to identify critical controls points along the value chain and describe potential risk mitigation measures that may be implemented at those points. The control of diseases of tilapia requires a multi‐faceted approach, with risk‐based control measures chosen based on their feasibility, effectiveness and sustainability. The Progressive Management Pathway for Improving Aquaculture Biosecurity, as a risk‐based, collaborative and progressive management approach combined with the systematic preventive principles of Hazard Analysis Critical Control Point, offers a strategic and practical way of improving biosecurity in the tilapia value chain.

Domestic cat hepadnavirus (DCH) is an emerging virus related to the hepatitis B virus (HBV). The pathogenic potential of DCH in cats remains to be established. The molecular prevalence of DCH varies widely in the regions investigated so far. The aim of this study was to determine the prevalence, load, and risk factors for DCH detection among cats in Hong Kong, and to generate molecular and epidemiological data on the DCH strains circulating in cats in Hong Kong. DCH DNA was detected using DCH-specific qPCR in 57/513 (11.1%) residual diagnostic blood samples from owned cats. The median viral load was 8.85 × 10³ copies/mL of whole blood (range for the 5th to the 95th percentile, 3.33 × 10³ to 2.2 × 10⁵ copies per mL). Two outliers had higher viral loads of 1.88 × 10⁷ copies/mL and 4.90 × 10⁹ copies/mL. DCH was detected in cats from 3 months to 19 years of age. Sex, age, neuter status, breed, or elevated serum alanine aminotransferase were not statistically associated with DCH DNA detection. On phylogenetic analysis based on 12 complete genome sequences, the Hong Kong DCH viruses clustered in Genotype A with viruses from Australia and Asia (clade A1), distinct from viruses from Europe (clade A2). Sequence analysis found that DCH has similar epsilon and direct repeat regions to human HBV, suggesting a conserved method of replication. Based on our findings, the DCH strains circulating in Hong Kong are a continuum of the Asiatic strains.