Aquatic Animal Diseases Research Articles

Characterization of a Bacillus velezensis with antibacterial activity and inhibitory effect on common aquatic pathogens

The strain CPA1–1 with better antibacterial ability was isolated and screened from healthy Macrobrachium nipponense by spot inoculation for the first time. It was identified as Bacillus velezensis through morphological, physiological and biochemical characteristics in combination with 16S rRNA and gyrB sequence analysis. The characteristics of growth, antimicrobial spectrum, the carrying of antibiotic-related genes and safety analysis of the strain were also studied. The results showed that the optimal growth temperature of strain CPA1–1 was 25–37 °C, and the growth of the strain was slow under 20 °C. The optimum pH value was 5–9, and the strain was severely inhibited when the pH was lower than 3 or higher than 11. The strain CPA1–1 could grow at a salinity of 5–60‰, and the optimal salinity was 5–20‰. CPA1–1 has better antibacterial effects on indicator bacteria, Aeromonas veronii, Plesimonas shigelloides, Aeromonas hydrophila, Vibrio parahaemolyticus, Citrobacter freundii, and the average diameter of the inhibition zones were 31.2 mm, 26.5 mm, 23.3 mm, 21.4 mm and 10.5 mm, respectively. Through PCR amplification, the results showed that B. velezensis CPA1–1 carried genes encoding the biosynthesis of various peptidoglycans, polyketone compounds and antimicrobial proteins, such as srfAA, ituA, fenA, dhbA, bmyA, beaS, and dfnA. Besides, the minimum inhibitory concentration of the fermented liquid of strain CPA1–1 against A. veronii, P. shigelloides, A. hydrophila, V. parahaemolyticus and C. freundii were 104 to 106 CFU/mL. The results of the safety test showed that the strain CPA1–1 had no adverse effects on M. nipponense, Siniperca chuatsi, Eriocheir sinensis and Procambarus clarkii. The strain CPA1–1 screened in this study has the good antibacterial ability. Therefore, it has the potential application prospects to prevent and control a variety of aquatic animal diseases.

Complete genome sequence analysis of the Vibrio owensii strain SH-14 isolated from shrimp with acute hepatopancreatic necrosis disease.

Vibrios are a group of very important bacterial pathogens in marine aquaculture industry and cause serious aquatic animal diseases, such as shrimp acute hepatopancreatic necrosis disease (AHPND). A new AHPND pathogen, the Vibrio owensii strain SH-14, was isolated from diseased shrimp in Shanghai, China. In this study, to better understand the pathogenesis of AHPND at the genomic level, the genome of the strain SH-14 was completely sequenced and analyzed. The SH-14 consists of two circular chromosomes of 3,689,702bp and 2,430,445bp, and of two plasmids named as pVHvo (69,148bp) and pVHvo-R (78,918bp), respectively. The pVHvo encodes the bi-toxic genes of pirAB, responsible for shrimp AHPND. The whole genomes contain a total of 5703 predicted open reading frames (ORFs), 129 tRNA genes and 37 rRNA genes. The average nucleotide identities (ANIs) between the SH-14 and the other V. owensii strains are all greater than 95%, confirming a new V. owensii strain of the SH-14. The taxonomic affiliation of the SH-14 is also supported by whole-genome alignment and nucleotide identity dotplot analyses. These results pave the way for further study of spread and epidemic of shrimp AHPND.

An oral delivery system for controlling white spot syndrome virus infection in shrimp using transgenic microalgae

White spot disease (WSD) is a longstanding and serious viral disease of various shrimp species that has caused high mortality rates for many decades. Currently, there is no practical method to control this disease. Therefore, we have explored the development of a novel vaccine-based method to control this disease using transgenic algae. During infection by white spot syndrome virus (WSSV), the interaction between viral envelope proteins and cell surface protein receptors on target cells is the key step of viral entry and replication. Hence, transgenic lines of the green microalga Chlamydomonas reinhardtii harbouring a WSSV VP28 viral envelope protein were created as an oral delivery system for vaccinating shrimp. Two separate transplastomic lines containing wild-type and codon optimized gene sequences for VP28 were evaluated for recombinant protein levels. Only the codon optimized line gave rise to detectable VP28 in western blot analysis, which demonstrated that optimization for chloroplast codon bias improved the efficiency of expression and that the gene design produced a favourable RNA secondary structure with suitable free energy for translation. In addition, bile salt and acid tolerance tests demonstrated that this transgenic Chlamydomonas can tolerate mildly acidic (pH 5.0) conditions and 0.30% bile salts. These features indicated that algal cells are suitable for delivering viral antigens through a shrimp's digestive system. In WSSV infection experiments, the highest survival rate (87%) was recorded in shrimps fed with the codon optimized VP28 line mixed into their feed, indicating that this line could be employed in the control of WSSV spread in shrimp populations. This algal strategy offers a new, efficient, fast and less labour-intensive method for the control of other diseases in aquatic animals through oral delivery.

Public–private partnership: responsibility for managing aquatic animal diseases

Public–private partnership: responsibility for managing aquatic animal diseases

An Update on the Genus Aeromonas: Taxonomy, Epidemiology, and Pathogenicity

The genus Aeromonas belongs to the Aeromonadaceae family and comprises a group of Gram-negative bacteria widely distributed in aquatic environments, with some species able to cause disease in humans, fish, and other aquatic animals. However, bacteria of this genus are isolated from many other habitats, environments, and food products. The taxonomy of this genus is complex when phenotypic identification methods are used because such methods might not correctly identify all the species. On the other hand, molecular methods have proven very reliable, such as using the sequences of concatenated housekeeping genes like gyrB and rpoD or comparing the genomes with the type strains using a genomic index, such as the average nucleotide identity (ANI) or in silico DNA–DNA hybridization (isDDH). So far, 36 species have been described in the genus Aeromonas of which at least 19 are considered emerging pathogens to humans, causing a broad spectrum of infections. Having said that, when classifying 1852 strains that have been reported in various recent clinical cases, 95.4% were identified as only four species: Aeromonas caviae (37.26%), Aeromonas dhakensis (23.49%), Aeromonas veronii (21.54%), and Aeromonas hydrophila (13.07%). Since aeromonads were first associated with human disease, gastroenteritis, bacteremia, and wound infections have dominated. The literature shows that the pathogenic potential of Aeromonas is considered multifactorial and the presence of several virulence factors allows these bacteria to adhere, invade, and destroy the host cells, overcoming the immune host response. Based on current information about the ecology, epidemiology, and pathogenicity of the genus Aeromonas, we should assume that the infections these bacteria produce will remain a great health problem in the future. The ubiquitous distribution of these bacteria and the increasing elderly population, to whom these bacteria are an opportunistic pathogen, will facilitate this problem. In addition, using data from outbreak studies, it has been recognized that in cases of diarrhea, the infective dose of Aeromonas is relatively low. These poorly known bacteria should therefore be considered similarly as enteropathogens like Salmonella and Campylobacter.

Tình hình sử dụng thảo dược trong nuôi tôm vùng Đồng bằng sông Cửu Long

Herbal plants are used to improve health, prevent and treat aquatic animal diseases, especially in marine shrimp farms in the Mekong Delta. However, detailed information on the use of herbal plants in shrimp farming in the Mekong delta is limited. This kind of information is important in the assessment of the characteristics, needs and potential use of herbal plants for the marine shrimp industry. The current study reports on a survey conducted in 2018 into the current use of herbal plants in shrimp farming. Ninety shrimp farmers in Ca Mau and Soc Trang provinces participated in the survey. Results showed: (i) herbal plants were used in both intensive shrimp farming in earthen ponds and super-intensive shrimp farming in plastic-lined ponds. The percentages of farmers using herbal plants in Ca Mau and Soc Trang were 58% and 51%, respectively; (ii) 18 herbal plant species were used in the shrimp farming process. (iii) the enhancement of shrimp immune system was the reason for application of herbal plants by most of shrimp farmers, followed by antibacterial activity of herbal plants; (iv) in Ca Mau, the group of farmers using herbs reported differences in the size of the harvested shrimp, costs and profits compared to those in the herb-nonuse group. It can be concluded that the use of herbal plants in marine shrimp farming in the Mekong Delta has demonstrated positive effects and has the potential to become widespread in a near future.

Complete genome analysis of Vibrio mimicus strain SCCF01, a highly virulent isolate from the freshwater catfish

ABSTRACT Vibrio mimicus is a foodborne pathogen, which is widely distributed in the aquatic environment. Moreover, it is often involved in aquatic animal diseases. In recent years, V. mimicus is an emerging pathogen in some species of Siluriformes. The strain SCCF01 was isolated from yellow catfish (Pelteobagrus fulvidraco). In this study, we aimed to perform genomic analysis of V. mimicus strain SCCF01 to identify genetic features and evolutionary relationships. Information on gene function and classification was obtained by functional annotation, and circular graph of strain SCCF01 genome, which was created by Circos v0.64. Information on virulence genes (adhesion, flagellum system, exotoxin, and secretory system, etc.) was obtained by virulence genes annotation. Genome element prediction showed that most of the mobile elements were distributed in chromosome I. Therefore, chromosome I of SCCF01 genome has more plasticity than chromosome II and might be larger in size. Genomic linear relationship between the strain of V. mimicus and strain SCCF01 was analyzed by linear pairwise comparison but was unable to determine the relationship. Gene family analysis predicted that the evolutionary direction of strain SCCF01 was: clinical strain → environmental strain → SCCF01 strain. Phylogenetic analysis showed that the strain SCCF01 was more closely related to environmental strains. According to gene family analysis and phylogenetic analysis, we speculated that strain SCCF01 has probably diverged from environmental strains.

Novel peptide nucleic acid-based real-time PCR assay for detection and genotyping of Megalocytivirus

Megalocytivirus, the causative agent for Red Sea Bream Iridoviral Disease (RSIVD), is classified into three genotypes based on its phylogeny: Red Sea Bream Iridovirus (RSIV), Infectious Spleen and Kidney Necrosis Virus (ISKNV), and Turbot Reddish Body Iridovirus (TRBIV). To overcome drawbacks such as limitation of genotypic variant type discrimination and unexpected PCR reaction from an SYBR green-based genotyping method by high-resolution melting analysis, peptide nucleic acid (PNA)-based real-time PCR assay for detecting and genotyping Megalocytivirus was developed. Compared with DNA hybridization, PNA has more suitable hybridization traits that allowed the difference in melting temperature (Tm) even by a single nucleotide mismatch. Based on the consensus sequences of the viral major capsid protein gene, four PNA probes labeled with respective fluorescence at their 3′ ends were designed as reporter molecules. PNA-based real-time PCR assay allowed quantification of Megalocytivirus copies using a synthetic DNA as standard (detection limit of 103 copies) and discrimination of the genotypes based on Tm in a single-tube reaction. Furthermore, the results of this new method were consistent with those of sequencing analysis of Megalocytivirus-infected field and artificial samples, proving its accuracy and efficiency. The novel PNA-based real-time PCR assay could contribute to the detection as well as discrimination of the genotypes of Megalocytivirus in a single simple assay, and could be used as a highly robust diagnostic tool in the field of aquatic animal diseases.

Assessment of economic loss due to fish diseases in Assam, India and implications of farming practices

Extensive surveys were conducted in 60 fish farms in Cachar and Nagaon districts of Assam, India to assess economic loss due to aquatic animal diseases and the contribution of fish farming practices therein. Epizootic Ulcerative Syndrome (EUS), also known as mycotic granulomatosis or red spot disease, was the most common disease that affected most fish species during winter months. Other disease conditions reported were dropsy, fin/tail rot and Argulus infestation. Overall disease prevalence was less in Cachar district compared to that in Nagaon district. Estimated loss of fish production (as percentage of total production) and total economic loss (in INR) were estimated to be 10.8% & 67,500.0 per farm (30,770.0 per ha) in Cachar and 5% & 55,300.0 per farm (14,900.0 per ha) in Nagaon district.The average farm area, water area and the number of ponds (per farmer) were less in Cachar compared to that in Nagaon district. Average fish production was also lower (1870 kg ha-1) in Cachar compared to Nagaon (2470 kg ha-1). The majority of fish farms in Cachar (60%) operated as a nursery (N) and grow-out (G) systems whereas those in Nagaon operated as nurseryfingerling-growout (N-F-G) system (63.33%). An overwhelming majority of farmers (93.33%) in Cachar practiced polyculture, but 30% of farmers practiced integrated farming in Nagaon district. N-F-G farming system and integrated culture practice adopted by the majority of Nagaon farmers led to higher fish productivity and lesser economic loss. Poor pre-stocking management of fish ponds was found to be the main contributory factor for higher disease prevalence in Nagaon compared to that in Cachar district. However, the farmers in Nagaon district were more aware of disease control measures that resulted in moderate economic loss. Key words Aquaculture practices, Fish diseases, Economic loss, Assam

Effect of extracts of luffa cylindrica, xanthosoma sagittifolium and momordica charantia on saprolegnia spp. Mycelial growth

Among the major infectious diseases in fish, those caused by zoosporic organisms are important, especially saprolegniasis. These diseases can affect few animals or even the entire population of the production environment. The use of alternative treatments for infectious diseases in aquatic animals has proven to be effective. It prevents the mortality of part of the crop, as well as the contamination of water by chemical components. Within this scenario, the use of plants stands out, mainly unconventional food plants (UFPs). The objective of this work was to evaluate the effect of the aqueous extracts of Luffa cylindrica, Xanthosoma sagittifolium and Momordica charantia on the mycelial growth of Saprolegnia spp. The extracts obtained from the maceration of dry and ground leaves were incorporated into the potato agar dextrose (PDA), at concentrations of 0, 5, 15, 25 and 50%. Later, filter paper disks containing the mycelium of Saprolegnia spp. were applied on the agar and incubated at 25°C. Evaluations were performed every 24 hours, for 10 days. In the study, all concentrations of M. charantia extract had an inhibitory action on the mycelial growth in the order of 75% of Saprolegnia spp. and can be considered a promising alternative for controlling this pathogen.

Visual and rapid detection of Plesiomonas shigelloides using loop-mediated isothermal amplification method.

Plesiomonas shigelloides is a common pathogen of aquatic animals and can pose a certain hazard to aquaculture. Here, we aimed to develop a loop-mediated isothermal amplification (LAMP) method for the visual detection of P. shigelloides to aid the diagnosis of infections caused by this pathogen in aquatic animals. We used LAMP to amplify P. shigelloides DNA and combined it with calcein or nucleic acid dipstick assay (NADA) to visualize the amplified products. The optimal LAMP amplification temperature was 64°C, and the reaction lasted for 50min. The limit of detection of recombinant plasmids containing the target gene using the LAMP method was 2·0×102 copies per μl, which is ten times higher than that using conventional polymerase chain reaction (PCR). LAMP products could be visualized without agarose gel electrophoresis. We tested 85 fish specimens using the established LAMP method and conventional PCR. The detection rate was 42·4% using the LAMP method and 34·1% using conventional PCR. Based on our results, the LAMP method combined with calcein or NADA is a rapid, specific, sensitive and accurate method for visual detection of fish-derived P. shigelloides and can be used for the laboratory diagnosis of infections caused by it. SIGNIFICANCE AND IMPACT OF THE STUDY: The combination of loop-mediated isothermal amplification (LAMP) and calcein and nucleic acid dipstick assay (NADA) provided a rapid, specific and sensitive method for detecting Plesiomonas shigelloides, which is an important pathogen that causes diseases in aquatic animals worldwide. In the present study, the LAMP method showed a higher detection rate than conventional PCR for P. shigelloides using templates from 85 fish specimens. Thus, the LAMP method could be a reliable and convenient tool for diagnosing diseases in aquatic animals in the laboratory.

To pool or not to pool? Guidelines for pooling samples for use in surveillance testing of infectious diseases in aquatic animals.

Samples from multiple animals may be pooled and tested to reduce costs of surveillance for infectious agents in aquatic animal populations. The primary advantage of pooling is increased population-level coverage when prevalence is low (<10%) and the number of tests is fixed, because of increased likelihood of including target analyte from at least one infected animal in a tested pool. Important questions and a priori design considerations need to be addressed. Unfortunately, pooling recommendations in disease-specific chapters of the 2018 OIE Aquatic Manual are incomplete and, except for amphibian chytrid fungus, are not supported by peer-reviewed research. A systematic review identified only 12 peer-reviewed aquatic diagnostic accuracy and surveillance studies using pooled samples. No clear patterns for pooling methods and characteristics were evident across reviewed studies, although most authors agreed there is a negative effect on detection. Therefore, our purpose was to review pooling procedures used in published aquatic infectious disease research, present evidence-based guidelines, and provide simulated data examples for white spot syndrome virus in shrimp. A decision tree of pooling guidelines was developed for use by peer-reviewed journals and research institutions for the design, statistical analysis and reporting of comparative accuracy studies of individual and pooled tests for surveillance purposes.

Impacts of epizootic ulcerative syndrome on subsistence fisheries and wildlife.

Epizootic ulcerative syndrome (EUS), caused by the water mould (Oomycota) Aphanomyces invadans, has spread throughout the world's major continents over the last 50 years, with the apparent exception of South and Central America. With over 160 susceptible fish species representing 54 families and 16 orders recorded to date, EUS is of international concern and infection with A. invadans is a World Organisation for Animal Health (OIE) listed disease. This paper examines what little has been reported on the impacts of EUS on subsistence fisheries and wildlife, or what can be deduced about those impacts, and concludes that there is a need for systematic data collection on the size and socio-economic importance of subsistence fisheries. Such fisheries are often relied upon by the poorest communities, thus food and nutrition security impacts can be significant. Similarly, impacts on wildlife are poorly documented, emphasising the lack of, and the need for, research on and modelling of the ecosystem-level impacts of EUS and other aquatic animal diseases. The history of EUS and several other aquatic animal diseases also brings into question the effectiveness of current measures for controlling the international spread of aquatic animal diseases and calls for a re-think on how best to meet this ongoing challenge.

Sharing responsibility between public and private sectors for the management of aquatic emergency animal diseases.

Aquatic animal disease outbreaks affect both the public (represented by the government) and the private sector (represented by the aquaculture and fisheries industry). However, all too often, the responsibilities and costs of responding to an outbreak may not be shared. Without a mechanism for public and private sectors to work together, the outcomes of an emergency response may not be ideal, or of common benefit to all potentially affected parties. In Australia, a mechanism is being developed for public and private sectors to share the responsibilities and costs of responding to aquatic animal disease outbreaks, through an industry- government aquatic emergency animal disease response agreement. The agreement provides an approach for both public and private sectors to share the responsibilities and costs of responding to a disease outbreak and to coordinate disease prevention activities to reduce their shared risk. The key elements of the agreement include provisions to incentivise faster notification of disease outbreaks, facilitate a faster response, share decision-making and costs (including compensation for affected businesses), clarify the responsibilities of all parties and, most importantly, strengthen risk mitigation activities. This paper describes how the draft agreement has been developed among 18 industry and government parties, how key elements of the agreement may contribute to improved aquatic animal health outcomes, and the principles which could be applied by other OIE Member Countries.

Measuring the impacts of aquatic animal diseases: the role of economic analysis.

Aquaculture is an important industry both economically and socially. The majority of this industry is focused on the production of aquatic animals, which may be substantially adversely affected by disease. Economic analyses may be used to inform decision-makers on the aquatic animal disease control choices that are economically optimal. Examples of such analyses are presented in this paper, ranging from basic cost estimates of disease impact to complex, spatial- temporal, bio-economic models. Regardless of the complexity of the analysis, there is a consistent need to collect and analyse good quality data measuring both the production and health of aquatic animals. This would require a variety of individuals and groups, including farmers, scientists and the government, to collaboratively contribute to this end. Given the necessary data, more sophisticated models may be better used to inform decision-making from the farm to the national level. Finally, economic analyses should not be limited to simple aggregated cost and benefit results but rather should include the social and gender impacts of financial decisions, as well as the potential externalities both within and among the various impacted sectors in order to optimise investment at both the farm and national levels.

The aquatic animal pandemic crisis.

The growth of aquaculture over the past 50 years has been accompanied by the emergence of aquatic animal diseases, many of which have spread to become pandemic in countries or continents. An analysis of 400 emerging disease events in aquatic animals that were logged by the Centre for Environment, Fisheries and Aquaculture Science between 2002 and 2017 revealed that more than half were caused by viruses. However, in molluscs, most events were parasitic. Categorising these events indicated that the key processes underpinning emergence were the movement of live animals and host switching. Profiles of key pathogens further illustrate the importance of wild aquatic animals as the source of new infections in farmed animals. It is also clear that the spread of new diseases through the largescale movement of aquatic animals for farming, for food and for the ornamental trade has allowed many to achieve pandemic status. Many viral pathogens of fish (e.g. infectious salmon anaemia, viral haemorrhagic septicaemia) and shrimp (e.g. white spot syndrome virus) affect a large proportion of the global production of key susceptible species. Wild aquatic animal populations have also been severely affected by pandemic diseases, best exemplified by Batrachochytrium dendrobatidis, a fungal infection of amphibians, whose emergence and spread were driven by the movement of animals for the ornamental trade. Batrachochytrium dendrobatidis is now widespread in the tropics and subtropics and has caused local extinctions of susceptible amphibian hosts. Given the rising demand for seafood, aquacultural production will continue to grow and diseases will continue to emerge. Some will inevitably achieve pandemic status, having significant impacts on production and trade, unless there are considerable changes in global monitoring and the response to aquatic animal diseases.

Vulnerabilities in aquatic animal production.

The role of aquatic animals in global food and nutrition security is increasingly recognised. The global demand for fish is increasing, leading to a need to significantly increase its supply. Securing future fish supplies through sustainable production is a challenge as major resources such as fresh water and land are becoming limited worldwide. Aquaculture and capture fisheries face various threats from both human-mediated and natural environmental change, including climate change. Aquaculture systems and practices are vulnerable to such changes. Moreover, aquatic animal diseases are currently considered one of the most important constraints to sustainable global fish production. The need to increase global production, combined with climate change, may increase losses due to diseases. This paper examines key vulnerabilities, their impacts and management to achieve increased and sustainable global fish production. The authors focus on the need to apply international standards, and to develop biosecurity and capacity in aquatic animal health to improve global fish health. Research needed to underpin the development of improved detection and control of fish diseases is also discussed.

A new approach to the management of emerging diseases of aquatic animals.

Since 1970, aquaculture has grown at a rate of between 5% and 10% per annum. It has achieved this by expanding into new areas, farming new (often non-native) species and intensifying production. These features of aquaculture, combined with large-scale movements of animals, have driven disease emergence, with negative consequences for both production and biodiversity. Efforts to improve the management of emerging diseases of aquatic animals must include actions to reduce the rate of disease emergence, enhance disease detection and reporting, and improve responses to prevent disease spread. The rate of disease emergence can be reduced by understanding the underpinning mechanisms and developing measures to mitigate them. The three principal mechanisms of disease emergence, namely, host switching, decreased host immunocompetence and increased pathogen virulence, have many drivers. The most important of these drivers are those that expose susceptible hosts to novel pathogens (e.g. the introduction of non-native hosts, translocation of pathogens, and increased interaction between wild and farmed populations), followed by host switching. Exposure to wild populations can be reduced through infrastructure and management measures to reduce escapes or exclude wild animals (e.g. barrier nets, filtration and closed-confinement technology). A high standard of health management ensures immunocompetence and resistance to putative new pathogens and strains, and thus reduces the rate of emergence. Appropriate site selection and husbandry can reduce the likelihood of pathogens developing increased virulence by preventing their continuous cycling in geographically or temporally linked populations. The under-reporting of emerging aquatic animal diseases constrains appropriate investigation and timely response. At the producer level, employing information and communications technology (e.g. smartphone applications and Cloud computing) to collect and manage data, coupled with a farmer-centric approach to surveillance, could improve reporting. In addition, reporting behaviours must be understood and disincentives mitigated. At the international level, improving the reporting of emerging diseases to the World Organisation for Animal Health allows Member Countries to implement appropriate measures to reduce transboundary spread. Reporting would be incentivised if the global response included the provision of support to low-income countries to, in the short term, control a reported emerging disease, and, in the longer term, develop aquatic animal health services. Early detection and reporting of emerging diseases are only of benefit if Competent Authorities' responses prevent disease spread. Effective responses to emerging diseases are challenging because basic information and tools are often lacking. Consequently, responses are likely to be sub-optimal unless contingency plans have been developed and tested, and decision-making arrangements have been well established.

Trade of aquatic animals and aquatic animal products: the use of OIE international standards for devising sanitary measures.

The World Organisation for Animal Health (OIE) develops international standards for the prevention, detection and control of aquatic animal diseases as well as the safe international trade of amphibians, crustaceans, fish, molluscs and their products. The Competent Authorities of importing and exporting countries should implement the OIE international standards by adopting the required legislation as this provides the basis for setting sanitary measures that ensure safe international trade, while avoiding unjustified sanitary barriers to trade. Based on an analysis of legislation notified by countries to the World Trade Organization (WTO) in the context of the Agreement on the Application of Sanitary and Phytosanitary Measures (SPS Agreement), the authors explore how and to what extent Member Countries use the OIE international standards when developing sanitary measures. The study develops an analytical framework for collecting and presenting countries' legislation to determine if a direct link can be demonstrated between national legislation and OIE international standards. Results show that OIE international standards are implemented through different categories of legislation which range from more general (those providing a general sanitary framework) to more specific (those setting requirements for the import of aquatic animals and aquatic animal products). However, the study illustrates the difficulty of identifying direct links between countries' legislation and OIE international standards. Nonetheless, this study is the first step in the design of an approach to better understand how OIE international standards are used by Member Countries to devise sanitary measures in the context of international trade. It further notes that increased transparency of national sanitary legislation can facilitate efforts to improve knowledge on the implementation of OIE international standards.

Building a sustainable aquaculture industry in South Africa: the role of biosecurity.

Progress towards the South African Government's social upliftment targets on food security, equity, job creation and economic development can be made by diversification of fish production in the country's aquaculture sector. The risks associated with the diseases and parasitic infections that affect aquaculture production in South Africa are poorly understood. Substantial investment is currently being made to provide evidence of freedom from OIE-listed diseases to support an aquaculture industry that is largely reliant on access to foreign markets for high-value aquacultural products. The projected rapid expansion of the aquaculture sector in South Africa accentuates the associated need to prevent the spread of aquatic animal diseases. The primary constraint is that the current regulatory framework governing aquacultural activities is not centralised due to the diversity of aquaculture activities spanning marine, brackish and freshwater environments. An aquaculture development bill was drafted in 2018 to promote aquacultural development. The effective implementation of the provisions of the bill requires resources to ensure that suitable standards for aquatic animal health management are achieved in accordance with international standards and government policies and objectives.