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NO44 - 3

International Trade in Aquatic Animals and Aquatic Animal Health: What Lessons Have We Learned So Far in Managing the Risks?

<>Melba G. Bondad-Reantaso*, Audun Lem and Rohana P. Subasinghe<>Department of Fisheries and Aquaculture, Food and Agriculture Organization of the United
Nations (FAO), Viale delle Terme di Caracalla 00153 Rome, Italy

ABSTRACT―Aquatic animals and their products are among the most widely traded commodities where some 40 percent of global production enters the international market. The international trade in aquatic animals and their products are carried out for various reasons. A number of aquatic animal health threats and risks in the international movement of live aquatic animals include the emergence of new pathogens due to the rapid development of aquaculture, limitations in control options for aquatic animal diseases, occurrence of multi-factorial disease syndromes, frequent sub-clinical infections in aquatic animals, undomesticated status of aquatic animals and little information available on biological requirements and health status, etc. In addition to these, because of the volume of live aquatic animals traded internationally, the diversity of species being moved, the many known and potential pathogens that infect aquatic species, the lack and/or weak enforcement of regulations and in other cases, lack of sector regulations itself- it has been a difficult task to find ways that will reduce the risks of spreading transboundary pathogens. This paper looks at the lessons learned and future challenges in managing the risks of disease incursion associated with the international trade of live aquatic animals.

Key words: international trade, aquaculture, aquatic animal health, biosecurity, risk analysis, transboundary aquatic animal diseases (TAADs)

International Epidemiology of Mollusc Diseases: Learning the Lessons from Two Recent Assessments on Susceptible and Vector Species by the European Food Safety Authority

<>Franck C. J. Berthe* and Ana Afonso<>Animal Health and Welfare (AHAW) Panel, European Food Safety Authority (EFSA), Largo N. Palli 5/A, 43100 Parma, Italy

ABSTRACT―Describing diseases in populations is the literal aim of epidemiology. From that point of view, molluscs and mollusc diseases put epidemiologists and other related 登gists・under serious challenges. Two recent assessments conducted by the Animal Health and Welfare (AHAW) Panel of the European Food Safety Authority (EFSA) have highlighted some of these challenges. In an attempt to establish a list of species susceptible to certain diseases, a set of objective criteria pertaining to pathogen replication, viability, host response and pathology, were established. Screening the peer-reviewed literature to document these criteria revealed that studies on diseases of molluscs and techniques applied to case investigation usually provide a great deal of information. However, thorough identification of the pathogen is frequently lacking. In addition, application of the criteria has led to unexpected outcomes of the assessment when species usually regarded as susceptible do not fulfil the criteria. If not susceptibility, the presence of a pathogen in a host leaves very little space for interpretation. From the viewpoint of transfer of pathogens, susceptible species and biological vectors may present equivalent risks. The concept of vector has itself proved to be a subject for controversy and definitions in the international standards for health management have shown to be potentially misleading in assessing the risk of transferring pathogens via transfers of live animals. A second assessment of the AHAW panel to list potential vector species highlighted a range of situations from mechanical carriage to actual infection. Interestingly, some of the conclusions of this risk assessment were later comforted by experimental data. Both the lack of accurate identification of mollusc pathogens and inconsistency in host species categorization result in poor understanding of epidemiology of diseases in molluscs. These issues are illustrated by selected examples.

Key words: mollusc, epidemiology, diagnostic, infection, disease, susceptibility, definition, risk assessment

Duration and Booster Effect of Phylactic Response against White Spot Syndrome Virus Infection in Kuruma Shrimp Orally Administrated with Recombinant Viral Proteins, rVP26 and rVP28

<>Jun Satoh1, Toyohiko Nishizawa2* and Mamoru Yoshimizu2<>1Aquatic Animal Health Division, National Research Institute of Aquaculture,
Fisheries Research Agency, Oita 879-2602, Japan
2Faculty of Fisheries Sciences, Hokkaido University,
Hokkaido 041-8611, Japan
(Received June 16, 2008)

ABSTRACT―White spot syndrome virus (WSSV: a synonym of penaeid rod-shaped DNA virus, PRDV) is the causative agent of white spot disease (WSD: penaeid acute viremia, PAV), one of the most serious diseases affecting decapod crustaceans around the world. Recently, 賭uasi-immune response・was found in kuruma shrimp Penaeus japonicus, wherein individuals that naturally survived from WSD showed protection against a rechallenge with WSSV. The phylaxis against WSSV was also inducible by oral vaccination with recombinant WSSV proteins, rVP26 and rVP28. In the present study, kuruma shrimp orally vaccinated with rVPs were sequentially challenged with WSSV to evaluate onset and duration of phylactic response and booster effect. The phylactic response of shrimp against WSSV-challenge peaked at day 45 after the vaccination with rVP26 (RPS: 100%) and at day 55 with rVP28 (RPS: 93%), and decreased within 10-20 days. The phylaxis against WSSV-challenge was boosted by the secondary vaccination with homologous rVPs, but not by those with heterologous rVPs. The peaks of phylactic responses appeared at day 22 after the secondary vaccination more rapidly than those after the primary vaccination. These results demonstrated that the duration of phylaxis induced by oral vaccination with rVPs was relatively short, but could be extended by booster vaccination with homologous rVPs.

Key words: white spot syndrome virus, WSSV, quasi-immune response, kuruma shrimp, oral vaccination, phylaxis, booster effect, PRDV

Histopathology of Striped Jack Pseudocaranx dentex Experimentally Infected with Ochroconis humicola

<>Chutharat Munchan1, Osamu Kurata1, Shinpei Wada1, Kishio Hatai1*, Noriyoshi Nakaoka2 and Hidemasa Kawakami2<>1Laboratory of Fish Diseases, Nippon Veterinary and Life Science University, Tokyo 180-8602, Japan
2Ehime Prefecture Fish Disease Control Center, Ehime 798-0087, Japan
(Received August 1, 2008)

ABSTRACT―This study compared the histopathology of young striped jack Pseudocaranx dentex experimentally infected with the dematiaceous fungus Ochroconis humicola NJM 0472 with that of spontaneously infected fish. Moribund and freshly dead fish from both groups showed similar histopathology, and appeared to have been killed due to hyphae penetrating the visceral organs. Fish that survived the infection appeared to be able to suppress the fungal growth by well-established inflammatory reaction involving mycotic granulomas and granulation tissues. The results suggested that two types of O. humicola infection occur in young striped jack: an acute type infection, which is characterized by penetrating hyphae that cause direct tissue destruction and a chronic type infection, which is characterized by severe inflammatory reaction that causes functional disorders of the affected organs.

Key words: Ochroconis humicola, Pseudocaranx dentex, histopathology, experimental infection

Efficacy of High Water Temperature Treatment against Pseudodactylogyrus spp. Infection in Japanese Eel

<>Makoto Tanaka*, Takayuki Satoh and Hajime Matsuyama<>Hamanako Branch, Shizuoka Prefectural Research Institute of Fishery, Shizuoka 431-0214, Japan
(Received February 3, 2009)

ABSTRACT―We investigated seasonal changes in the abundance of Pseudodactylogyrus spp. (Pd) in Japanese eel Anguilla japonica in culture ponds. For this purpose, the number of parasite eggs floating in the rearing water was counted as an indicator. In spring, the average number of floating eggs was 40.3 (SD= 53.2) per liter of rearing water, which was maintained at 28-30゚C by heating. In summer, the water temperature increased up to 30゚C or higher without heating. During this period, the number of floating eggs was high at 30゚C and was low at > 32゚C. The number of floating eggs was the highest (maximum number of eggs, 1,678 per liter) in autumn when the temperature ranged from 23゚C to 30゚C. In winter, the number of eggs was again low. On the basis of these results, we reared eels infected with Pd in fresh water at 29゚C, 32゚C and 35゚C for 20 days to control this parasitic disease. Parasites did not decrease in number at 29゚C, but clearly decreased at 32゚C, and almost disappeared at 35゚C within 5 days. When heavily infected eels were maintained at 35゚C for 5 days in a greenhouse pond, mortality due to the infection clearly decreased.

Key words: Pseudodactylogyrus spp., Anguilla japonica, water temperature, control, seasonal change

Modification of KDM-2 with Culture-spent Medium for Isolation of Renibacterium salmoninarum

<>Takanori Matsui, Toyohiko Nishizawa* and Mamoru Yoshimizu<>Faculty of Fisheries Sciences, Hokkaido University, Hokkaido 041-8611, Japan
(Received May 8, 2009)

ABSTRACT―KDM-2 is a medium widely used for isolation of Renibacterium salmoninarum (R.s.), the causative agent of bacterial kidney disease (BKD). KDM-2 still has a problem for colonization of R.s. at low concentration levels. In the present study, we modified KDM by supplementation of the culture-spent medium of R.s. (SMRs) in substitution of FBS. No difference was observed in the growth rate of R.s. at > 103 cells/mL in KDM broth with 1% FBS regardless of SMRs supplementation. Growth rate of R.s. decreased at 101 cells/mL of inoculation into KDM with 1% FBS, but it was recovered by supplementation of > 1% SMRs into the medium. The activity of SMRs supporting bacterial growth was stable to treatment at 60゚C for 30 min and freezing at -20゚C for 7 days. At inoculation of < 300 CFU of R.s., expected colony counts were obtained on the agar plates containing SMRs, while non or less than half of bacteria colonized on the agar plates without SMRs. It was thus considered that the modified KDM by supplementation of SMRs instead of FBS was convenient and inexpensive for isolation of R.s., especially at low concentration levels.

Key words: Renibacterium salmoninarum, bacterial kidney disease, BKD, growth rate, colonization

Halioticida Infection Found in Wild Mantis Shrimp Oratosquilla oratoria in Japan

<>Hiroko Atami, Yasunori Muraosa and Kishio Hatai*<>Laboratory of Fish Diseases, Nippon Veterinary and Life Science University, Tokyo 180-8602, Japan
(Received May 13, 2009)

ABSTRACT―In December 2006, a Halioticida infection was found in wild mantis shrimp Oratosquilla oratoria in Tokyo Bay, Japan. Fungi were found in the gills of mantis shrimp, isolated from lesions using PYGS agar, and identified by morphological observation and molecular analysis. The fungi formed fragments in the hyphae and several discharge tubes developed from each fragment. Zoospores were formed within the fragments and released into the seawater through the tops of discharge tubes. Based on the characteristics of zoospore production mode, the fungi were classified into the genus Halioticida. Fungal isolates NJM 0642 and NJM 0643, isolated from mantis shrimp, were compared by molecular analysis of the D1/D2 region of the large subunit ribosomal RNA gene (LSU rDNA) with other fungi belonging to Peronosporomycetes, isolated from various marine crustaceans and abalones Haliotis spp. As a result, both isolates were identified as Halioticida noduliformans, which has been isolated from abalone. Moreover, experimental infection demonstrated that the fungus was pathogenic to mantis shrimp. This is the first report of fungal disease caused by Peronosporomycetes in mantis shrimp.

Key words: Halioticida noduliformans, fungal infection, Oratosquilla oratoria, mantis shrimp

Reovirus-like Infection of Cultured Summer Flounder Paralichthys dentatus

<>Shinpei Wada1*, Osamu Kurata1, Kishio Hatai1, Edward J. Noga2, Michael J. Dykstra3 and John S. Burke4<>1Laboratory of Fish Diseases, Nippon Veterinary & Life Science University, Tokyo 180-8602, Japan
2Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, USA
3Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, USA
4Coastal Ecology and Restoration, National Oceanic & Atmospheric Administration, National Ocean Service, Center for Coastal Fisheries and Habitat Research, Beaufort, NC 28516, USA
(Received May 29, 2009)

ABSTRACT―Examination via light and electron microscopy of juvenile summer flounder Paralichthys dentatus experiencing a subacute to chronic mortality revealed severe necrotizing hepatitis characterized by necrotic multinucleated giant cells (syncytia). The cytoplasms of syncytia contained paracrystalline arrays of reovirus-like particles, strongly suggesting that the epidemic was caused by the virus. This is the first report of a putative viral infection in summer flounder.

Key words: hepatic syncytia, Paralichthys dentatus, summer flounder, reovirus-like particles