The global captured fishery is at an all-time low, however, the rising world population and the increase in demand for seafood have led to the rapid growth of the aquaculture industry, including net-pen based salmon production. The aquaculture and fishing industries are challenged by changing ecosystems due to climate change as well as from an increase in the emergence, severity, and prevalence of infectious diseases in the aquatic ecosystem. The potential consequences of farming fish in the vicinity of native wild sympatric fish species is an ongoing debate and has led to the closure of some farm sites in Canada and can have ramifications for other farming regions and species in the absence of a social license. Climate change and infectious diseases are altering the population dynamics of many commercially and culturally important fisheries such as Atlantic and Pacific salmon, lobsters, etc. Many aquatic food animal diseases are associated with pronounced shifts in microbial community structures or genetic and functional changes in reservoir non-virulent progenitor variants. The long-term goal of my research program is to understand the effects of changing ecosystem, and the interaction of farmed and wild fish, by utilizing big data along with appropriate quantitative and epidemiologic tools, on infectious diseases of aquatic food animal species and ultimately to enhance the aquatic epidemiology research program for sustainable aquaculture and fishery. The short-term goal is to conduct prospective and retrospective on-farm (field) or in-silico studies to elucidate the interactions between host, pathogen(s), and environment to understand the occurrence, transmission, and risk factors associated with emerging or likely to emerging infectious diseases in salmon aquaculture and lobster fishery in Canada. Some of the key questions my current research is trying to answer are: what are the spatio-temporal trends in emergence and reemergence of infectious diseases of aquatic food animals, how abundant are non-virulent strains of infectious agents, and how likely are they to convert to virulent strains and result in clinical outbreaks? To what extent do the environmental and other factors interact with these microbial and genetic shifts and result in clinical disease? Are there factors that can be managed to reduce the impact of such diseases? My research uses molecular epidemiology (including microbiome analyses) to evaluate genetic differences between variants and strains of the infectious agents, and profile differences in microbial communities between healthy and clinical fish, applies epidemiological methods to identify the component causes/risk factors (specific agents, genotypes, variants, and strains) involved in the clinical manifestation of these diseases to help understand the complex causal pathway/s of the disease, investigates the association of environmental (water temperature, salinity, dissolved oxygen, and plankton), host (immune system, stress markers), and management factors with outbreaks of the diseases and employs simulation models to evaluate the effectiveness of different control and mitigation measures on the potential spread of infectious diseases between aquaculture sites. I will discuss and present some of my recent studies using these methods that will highlight the importance of epidemiologic research in addressing infectious disease and productivity issues in farmed and wild salmon, lobster, and shrimp.

[Veterinarians focus on Aquaculture]

At veterinary colleges in Japan, students take only one credit in fish pathology. It is a minor field in which only a few questions are asked in the national veterinary examinations. However, in the past five years, many veterinarians have focused on aquaculture. The reason for this is “the Strategy for the Growth Industry of Aquaculture in Japan” published by the MAFF in 2020. This strategy is a comprehensive strategy developed based on data on domestic and international needs for Japanese aquaculture products, covering everything from production to marketing and export. This means that Japan will make a full-fledged effort to promote the aquaculture industry in the future.

[Fishery Production]

According to statistics from the Food and Agriculture Organization of the United Nations (FAO), the global wild caught fisheries production has remained flat from around 1990 to the present. However, the ratio of aquaculture production (the ratio of aquaculture production to the total of wild caught fisheries production and aquaculture production), which was around 10% around 1970, has increased rapidly since 1990 and now exceeds 50%. This means that the global fisheries are shifting to aquaculture. On the other hand, Japan’s wild caught fisheries production peaked around 1990 and declined sharply, and is now about 1/3 of its peak level. Aquaculture production increased from around 1970, but has remained flat to date.

Looking at aquaculture production by country and species, Norway’s aquaculture production is dominated by marine fisheries, while China’s aquaculture production is dominated by inland water fisheries On the other hand, Japan’s aquaculture production is weak in fish, with algae and shellfish accounting for about 3/4 of the total.

[Fish species and Regional characteristics]

The species of fish farmed in Japan are extremely diverse. The major animal species in the livestock industry are cattle, pigs, and pigeons, but fish are classified into more than 10 orders. We need to learn several dozen species of fish, even just the major species that cause fish diseases. This classification is mainly anatomical and is not always consistent with classification by specificity and immunity to pathogens and reaction and persistence to pharmaceuticals. This inconsistency often leads to confusion when considering target fish species for fishery pharmaceuticals.

In the marine aquaculture, sea bass species are primarily farmed in the warm-water areas from the Kii-peninsula to Shikoku and Kyushu. In some cases, salmonids are farmed at sea in the cold-water areas of the Tohoku region. In inland water aquaculture, ayu-fish are farmed in inland areas, and eels are raised in the Tokai and Kyushu regions.

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To understand the biological characteristics of aquatic animals is required for a control of aquatic animal diseases. Aquatic animals including fish, crustacean and shellfish are poikilothermic animals and live in water, and these characteristics are quite different from that of terrestrial animals. Diagnosis and treatment in animals for aquaculture are curried out for whole animals in a facility/farm, but not for individuals except aquarium fish including koi that are much valuable. The purpose of the diagnosis is to identify the cause of death, and targets of the diagnosis are only exogenous diseases.

There are two strategies for infectious disease control in aquatic animals as well as terrestrial animals. One is a strategy to aim at eradication of causative agents in an area and the other is to treat animals by antibiotics or to prevent infections by vaccines without eradication of causative agents in environment. The former is an ideal strategy and OIE (International Organisation for Animal Health) designates 29 infectious diseases for aquatic animals as listed diseases and requires OIE member countries to establish quarantine systems against these diseases to prevent the diseases from spreading in the world due to international movement of animals. In Japan, 24 infectious diseases are designated for aquaculture animals that are susceptible to each disease as ‘pathogens of diseases subject to import quarantine’ which are determined under Fisheries Resources Protection Act. When Ministry of Agriculture, Forestry and Fisheries (MAFF) import a susceptible species to target diseases, the exporting country shall submit a health certificate for the diseases to meet sanitary conditions previously determined between two countries. The 24 infectious diseases are also designated as ‘specific diseases’ determined under Sustainable Aquaculture Production Assurance Act, and owners of farms shall notify the prefectural government if they suspect or identify fish infected by the specific diseases in their farms. The prefectural government that receives the notification can test the fish and direct the owner to stop transferring fish from the contaminated facility and to burn or bury them when the diseases are detected in the test. In the case that Japan Fisheries Research and Education Agency (FRA) diagnoses as the specific diseases, the owner can receive a compensation for disposed fish from the MAFF. Koi herpesvirus (KHV) disease, one of the specific diseases, first occurred in 2003 and spread in the whole country during the following year, but the number of the case has been decreasing recently due to the continuous prevention measures. Since countries that import koi from Japan require a health certificate to prove free from KHV in fish, the MAFF establishes the list for koi farms/facilities appropriate for exporting koi where two-time tests in every year are conducted to demonstrate frees from KHV disease and carp spring viremia (SVC) (compartmentalization).

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動物診療施設で飼い主に対して用いられる敬称，動物の性別，食餌の各表現について適切と認識されているか，またいずれの表現が好まれているか，全国280名の犬猫の飼い主をオンライン抽出して調査した。適切性と選好度はともに良好なものから順に，敬称は「（苗字）さん」「（苗字）さま」「（動物名）のお父さん・お母さん」，動物の性別は「男の子・女の子」「オス・メス」「男性・女性」，食餌は「ご飯」「フード」「エサ」となった。飼い主の属性と愛着尺度が適切性に及ぼす影響を構造方程式モデルで検証したところ，男性は「エサ」を高く，「男の子・女の子」「ご飯」「フード」を低く評価し，愛着尺度のうち依存的愛着得点が高い飼い主は「（動物名）のお父さん・お母さん」「男性・女性」を高く，「（苗字）さん」「オス・メス」を低く評価する傾向が認められた。

We have covered the use and interpretation of regression analysis for risk factor analysis in the last two articles. This article steps back and introduces a very traditional and basic analysis to explain the fundamental difference between confounding and interaction/effect modification. I explain the concept of Mantel-Haenszel (MH) estimator and its analytical method using a mock data. While the readers may not use MH estimator frequently, I hope this article explains the concept of stratification and meaning of variable selections in regression analyses.

Antimicrobial resistance has been attracting attention for a couple of decades as one of One Health issues of concern. UN Political Declaration on AMR in 2016 resulted in establishing new global governance structures on AMR where the environment sector is formally involved as an important pillar. Measures and discussions at technical levels are watched over by high-level global leaders and made open to non-technical civil society. The animal health sector should bear in mind this change of the setting.

The quantity of antimicrobial agents intended for use in animal has been steadily decreasing both at the global level and in the region of Asia and the Pacific. With more than 100 countries declaring that they do not use antimicrobials as growth promoter, the focus of the debate is how to limit the use for prevention and control of infectious diseases. In the field, efforts are needed to see if antimicrobials are imperative in each case. The revised Codex Code of Practice and OIE Codes currently under revision, and newly developed species-specific subdivisions of the OIE List of antimicrobial agents for veterinary importance should support such efforts. Monitoring actual use is needed to ensure responsible and prudent use.