With the rapid growth of the aquaculture production since the 1980s, there has been a concomitant increase in disease outbreaks. The injudicious and/or incorrect use of antimicrobial agents against diseases of farmed aquatic species poses a considerable threat to the development and growth of a successful and sustainable aquaculture industry. An increase in antimicrobial resistance (AMR) is an important consequence, resulting to the difficulty in treating common bacterial diseases in populations of aquatic organisms, combined with the presence of antibiotic residues in food fish and their products, leading to import refusals and negative impacts on international trade. To reduce the frequency of AMR, good aquaculture and effective biosecurity practices should include the prudent and responsible use of antibiotics and also consider the use of alternatives to antibiotics, in addition to disease prevention management. This article reviews the literature discussing the scope of the problem pertaining to antibiotic use, the emergence of AMR in aquaculture and to consider and discuss viable alternatives (e.g., vaccination, bacteriophages, quorum quenching, probiotics and prebiotics, chicken egg yolk antibody and medicinal plant derivative). We also discuss lessons learnt, from specific case studies such as the vaccination of farmed salmon in Norway and the use of ‘specific pathogen‐free’ seed—as primary and essential part of a biosecurity strategy.

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.

The present study aimed to investigate the quality of newly hatched broiler chicks delivered to Hong Kong (imported or local), and to develop tailored recommendations to improve their management. During 2019–2021, 70 batches (34 imported from mainland China and 36 local) of one/three day old chicks on 11 broiler farms were studied. From each batch, 23 or 24 chicks (1647 in total) were assessed for abnormalities in appearance, navel, crop filling, dehydration, body weight, and length uniformity. Chicks were sacrificed, and yolk sac residues in three day old chicks were measured. Maternally derived antibody levels against Newcastle disease virus (NDV), infectious bursal disease virus (IBDV), and avian reovirus (ARV) were measured in all chicks using an enzyme-linked immunosorbent assay (ELISA). The proportion of abnormal navel in most batches is high (median: 59%), ranging between 0 and 100%. The average length of chicks within batches ranges between 16.3 and 20.7 cm, and their average weights are 31–38.5 g upon delivery to the farms. On average, imported batches have a higher body weight and length than their local counterparts. The average yolk-free weight varies between 45 and 55 g, which is significantly lower in local batches (33–43 g). The mean antibody titers against NDV and ARV are higher in imported batches than in the local ones. In contrast, the mean antibody titer against IBDV is significantly lower in the imported batches. Concerning the overall lower quality of local chicks compared to the imported batches, establishing a well-managed broiler breeder farm and a hatchery in Hong Kong is highly recommended to enhance the health and productivity of the local broiler chicken industry.

Copper-based fungicides have a long history of usage in agriculture and aquaculture. With the rapid development of metal-based nanoparticles, copper-based nanoparticles have attracted attention as a potential material for prevention and control ofSaprolegnia parasitica. The present study investigated the effectiveness of copper/carbon core/shell nanoparticles (CCCSNs) and a commercial CCCSNs filter product (COPPERWARE^®) againstS. parasiticain a recirculating system. Results showed that the growth of agar plugs with mycelium was significantly suppressed after exposure to both CCCSNs powder and COPPERWARE^®filters. Even the lowest concentration of CCCSNs used in our study (i.e., 100 mg/mL) exhibited significant inhibitory effects onS. parasitica. The smallest quantity of the filter product COPPERWARE^®(3.75 × 3.7 × 1.2 cm, 2.58 g) used in our aquarium study also demonstrated significant inhibition compared with the control group. However, we observed leaching of copper into the water especially when larger quantities of COPPERWARE^®were used. Water turbidity issues were also observed in tanks with the filter material. Besides these issues, which should be further investigated if the product is to be used on aquatic species sensitive to copper, CCCSNs has promising potential for water disinfection.

Laser-induced graphene (LIG) has gained popularity for electrochemical water disinfection due to its efficient antimicrobial activity when activated with low voltages. However, the antimicrobial mechanism of LIG electrodes is not yet fully understood. This study demonstrated an array of mechanisms working synergistically to inactivate bacteria during electrochemical treatment using LIG electrodes, including the generation of oxidants, changes in pH-specifically high alkalinity associated with the cathode, and electro-adsorption on the electrodes. All these mechanisms may contribute to the disinfection process when bacteria are close to the surface of the electrodes where inactivation was independent of the reactive chlorine species (RCS); however, RCS was likely responsible for the predominant cause of antibacterial effects in the bulk solution (i.e., ≥100 mL in our study). Furthermore, the concentration and diffusion kinetics of RCS in solution was voltage-dependent. At 6 V, RCS achieved a high concentration in water, while at 3 V, RCS was highly localized on the LIG surface but not measurable in water. Despite this, the LIG electrodes activated by 3 V achieved a 5.5-log reduction in Escherichia coli (E.coli) after 120-min electrolysis without detectable chlorine, chlorate, or perchlorate in the water, suggesting a promising system for efficient, energy-saving, and safe electro-disinfection.

Despite ongoing efforts to improve aquaculture biosecurity in Ghana, farm-level compliance remains poorly understood. This study assessed biosecurity implementation levels by analyzing five years of routine biosecurity audit data from 235 fish farms across 12 regions. A structured questionnaire was used to collect data on farmer demographics, farm-level characteristics, and implementation of 14 biosecurity measures. Biosecurity scores were calculated for each farm and categorized as good (70-100, Grade A), moderate (40-69, Grade B), or poor (0-39, Grade C). Descriptive analyses and Kruskal-Wallis tests were used to explore associations in biosecurity compliance and farm-related factors. Findings revealed significant compliance challenges, with less than 5% of farms achieving a Grade A status. While most farms demonstrated relatively high compliance in feed storage (84.3%) and record-keeping (77.9%), implementation remained low for disinfection points (11.5%), Biosecurity Management Plans (6.4%), influent (3.8%) and effluent (13.2%) water treatment, and signages (11.5%). Biosecurity scores were significantly associated with geographical zone (p<0.001), production scale (p<0.001), operation type (p<0.001), culture facility (p<0.001), and species farmed (p=0.016). Grade C farms were predominantly small-scale, grow-out operations culturing African catfish in concrete or tarpaulin tanks, particularly in the Northern Belt, where 97% of farms had Grade C status. This study highlights a critical need for targeted interventions, extension services, and farmer education to improve compliance while also serving as a baseline to guide biosecurity adoption in Ghana.