School of Veterinary Medicine

Osamu Kurata

  (倉田 修)

Profile Information

Affiliation
Professor, Faculty of Veterinary Science, School of Veterinary Medicine, Nippon Veterinary and Life Science University
Degree
(BLANK)

J-GLOBAL ID
200901072207237875
researchmap Member ID
1000192391

Papers

 22
  • Goshi Kato, Hayato Nakajima, Kyuma Suzuki, Yuhei Kanzawa, Chihaya Nakayasu, Kosei Taguchi, Osamu Kurata, Motohiko Sano
    Frontiers in immunology, 14 1101491-1101491, 2023  Peer-reviewed
    INTRODUCTION: Temporal elevation of water temperature positively affects immune activity and disease resistance in poikilothermic teleost fish. The ayu, Plecoglossus altivelis, an important fish species for Japanese freshwater fisheries, is usually produced under higher water temperatures than the natural conditions to facilitate rapid growth. However, it has been reported that rearing fish at higher water temperatures inhibits the development of the thymus, suggesting that resistance to infectious diseases is reduced in ayu reared at higher water temperatures. Here, we show that decreased resistance to bacterial cold-water disease and excessive inflammatory responses occurred in ayu reared at 22°C compared with those reared at lower temperatures. METHODS: Ayu larvae were reared at 12°C, 15°C and 22°C for 77 days and fed 3% of their body weight. Thymus index and condition factor was calculated after the fish rearing. Then, ayu reared at the different temperatures were challenged with Flavobacterium psychrophilum and the fish were sampled for histopathology and gene expression analyses. Further, the fish were vaccinated with formalin-killed F. psychrophilum and continuously reared at the three different water temperatures. Serum antibody titer was determined by ELISA and cumulative mortality in each group was recorded after the bacterial challenge. RESULTS: Ayu reared at 22°C showed a significantly lower thymus index and higher condition factor than those reared at lower temperatures. Infiltrated leukocytes and many melanin pigments were frequently observed in the adipose tissues and spleens of ayu reared at 22°C, respectively, but not in those reared at 12°C. The gene expression levels of inflammatory cytokines such as IL-1β, IL-8 and TNFα in the spleen were significantly higher in the 22°C group than in the 12°C group. The cumulative survival rate after challenge with Flavobacterium psychrophilum was 51.7%, 40.0% and 13.3% in the 12°C, 15°C and 22°C groups, respectively. The relative percent survival values of vaccinated fish reared at 15°C and 22°C groups were lower than those reared at 12°C. Moreover, the specific antibody titer of the vaccinated fish was the lowest in the 22°C group and the highest in the 12°C group. DISCUSSION: These results suggest that rearing the fish under high water temperature causes excessive inflammatory responses similar to metabolic inflammation in human obesity, resulting in a decrease of disease resistance. In addition, thymic involution induced by higher water temperature probably leads the poor response to vaccination. The present study provides insights into the physiological and immunological changes of fish under global warming.
  • Kurata Osamu, Haneji Miyabi, Kawashima Takuya, Yagisawa Masaru, Saito Satoru, Mori Tatsuya
    Fish Pathology, 57(3) 95-102, Sep 15, 2022  Peer-reviewedLead authorCorresponding author
    The efficacy of Oxilink-SP, a food-additive-based disinfectant used in the environmental control of livestock pathogens, to prevent Saprolegnia infection of salmonid eggs was evaluated. ​In the laboratory, Oxilink-SP showed fungicidal activity against 5 species of Saprolegnia after immersion of rainbow trout Oncorhynchus mykiss eggs with Saprolegnia mycelia in a 10,000-fold dilution of Oxilink-SP for 30 min. ​In salmonid fish hatcheries, following immersion in a 5,000-fold dilution of Oxilink-SP for 30 min per day, hyphal growth on eggs of rainbow trout and white-spotted char Salvelinus leucomaenis was inhibited. ​This was not the case in masu salmon Oncorhynchus masou which may have been affected by water-borne molds of taxa other than Saprolegnia. ​Although rainbow trout eggs were slightly affected by treatment with Oxilink-SP in eyed-egg developmental stages and hatching, white-spotted char and masu salmon eggs were not affected. ​Furthermore, this treatment did not affect the incidence of fry deformity in all tested salmonid fish eggs. ​These results indicated that the disinfectant can prevent the spread of Saprolegnia species on salmonid eggs in hatcheries. ​We intend to use Oxilink-SP to safely manage fish eggs.
  • Osamu Kurata, Suyu Miyashita, Shinpei Wada
    Fish Pathology, 56(4) 216-219, Dec 15, 2021  Peer-reviewedLead authorCorresponding author
  • Osamu Kurata, Suyu Miyashita, Shusei Toda, Shinpei Wada, Takamitsu Sakai
    Fish Pathology, 55(4) 151-161, Jan 15, 2021  Peer-reviewedLead authorCorresponding author
  • Yozo Takada, Kosei Taguchi, Kyuma Suzuki, Akihiko Ashizawa, Koichi Kaji, Shun Watanabe, Shinpei Wada, Osamu Kurata
    Fish Pathology, 55(2) 31-37, Jun, 2020  Peer-reviewedCorresponding author
    The temperature of water used to rear juvenile stages of ayu affects the development of the thymus. However, subsequent differences in the thymus in adults after rearing juveniles at different temperatures are unclear. We analyzed thymus development of ayu grown at a constant water temperature of 15 degrees C from juveniles reared at different water temperatures. Juvenile ayu weighed at 0.6 g and 1.4 g were reared at different temperatures (10 degrees C, 12 degrees C, 15 degrees C, 18 degrees C and 22 degrees C) for 64 days and 54 days, respectively, and then held at 15 degrees C for analysis of the thymus development. Thymus volume was measured by computed tomography and thymus development of experimental fish was evaluated as the ratio of thymus volume to body length. The thymus volume ratios of juveniles immediately after rearing at lower water temperatures (10 degrees C, 12 degrees C) were higher than in those reared at the higher temperatures (18 degrees C, 22 degrees C). These levels of thymus volume ratio were preserved in grown ayu continuously reared at 15 degrees C. After the summer solstice, the thymus began to atrophy and no longer exhibited differences among the experimental groups. Thus the thymus formed at the juvenile stage retains its morphological properties until the summer solstice.

Misc.

 75
  • Takeshi Komine, Saralee Srivorakul, Mitsumi Yoshida, Yoshiaki Tanaka, Yuma Sugimoto, Mari Inohana, Hanako Fukano, Yoshihiko Hoshino, Osamu Kurata, Shinpei Wada
    Journal of fish diseases, 46(5) 507-516, May, 2023  
    Mycobacterium marinum is a slow-growing, photochromogenic nontuberculous mycobacterium, which can cause mycobacteriosis in various animals, including humans. Several cases of fish mycobacteriosis have been reported to date. Mycobacterium marinum has also been isolated from aquatic environmental sources such as water, sand, biofilms, and plants in the natural environments. Hence, we hypothesized that a wide variety of sources could be involved in the transmission of M. marinum. In this study, we tested this hypothesis by isolating M. marinum from various sources such as fish, invertebrates, seagrass, periphytons, biofilms, sand, and/or water in two aquaria in Japan and conducting a phylogenetic analysis based on single-nucleotide polymorphisms (SNPs) using whole-genome sequences of the isolated strains. The analysis revealed that the strains from animal and environmental sources belonged to the same clusters. This molecular-based study epidemiologically confirmed that various sources, including fish, invertebrates, and environmental sources, could be involved in transmission of M. marinum in a closed-rearing environment. This is the first report where M. marinum was isolated from different sources, and various transmission routes were confirmed in actual cases, which provided essential information to improve the epidemiology of M. marinum.
  • Takeshi Komine, Yuko Matsuoka, Mari Inohana, Osamu Kurata, Shinpei Wada
    Microbiology resource announcements, 12(3) e0113522, Mar 16, 2023  
    Mycobacterium chelonae is a nontuberculous mycobacterium that causes infections in various animals, including humans. In this study, we report the draft genome sequence of M. chelonae subsp. bovis strain NJB1701, which was isolated from a Baikal seal (Pusa sibirica) in captivity in Japan.
  • Takeshi Komine, Hyogo Ihara, Mari Inohana, Jennifer Caroline Kwok, Akane Shimizu, Tsumugi Terasawa, Ayaka Miyazaki, Saralee Srivorakul, Hajime Iwao, Sachiko Harada, Mitsunori Yoshida, Yoshihiko Hoshino, Osamu Kurata, Hanako Fukano, Shinpei Wada
    Frontiers in veterinary science, 10 1248288-1248288, 2023  
    INTRODUCTION: Mycobacterium montefiorense is one of the causes of non-tuberculous mycobacterial infections in moray eels and salamanders. Although M. montefiorense infection could be a threat to salamanders, little information is available regarding this pathogen and associated infection. This study aimed to provide fundamental information regarding M. montefiorense and its infection in salamanders. METHODS: Nine M. montefiorense strains isolated from three species of salamanders, namely, Japanese black salamander (Hynobius nigrescens), Hakuba salamander (H. hidamontanus), and Tohoku hynobiid salamander (H. lichenatus), between 2010 and 2018, were characterized based on phenotypic and genetic examination. We also pathologically observed salamanders infected with the M. montefiorense strains, including Hakuba salamanders and Tohoku hynobiid salamanders. RESULTS: The microbiological and chemical characteristics of the M. montefiorense salamander and an eel strain (reference strain) matched. Susceptibility testing for antimicrobials suggested that clarithromycin may be effective. Regarding disinfectants, phtharal, peracetic acid, glutaral, sodium hypochlorite, and benzalkonium chloride may be effective. Phylogenetic analyses revealed that the strains isolated from salamanders in 2014 and 2018 were genetically closely related, which could indicate an outbreak. The main gross findings in infected salamanders include skin ulcerative lesions or nodules in the enlarged liver. Microscopically, multifocal to coalescent granulomatous lesions composed of massive macrophages containing numerous acid-fast bacilli were prominently observed in the liver. CONCLUSION: This study contributes to our understanding of the genetic diversity and phenotypic characteristics of M. montefiorense, as well as the pathology of the infection.
  • Mari Inohana, Takeshi Komine, Yoshiaki Tanaka, Osamu Kurata, Shinpei Wada
    Journal of fish diseases, 46(1) 47-59, Jan, 2023  
    Mycobacterium marinum is a prevalent nontuberculous mycobacterium (NTM)-infecting teleosts. Conversely, little is known about mycobacteriosis in elasmobranchs, and M. marinum infection has never been reported from the subclass. This study investigated the histopathological characteristics and localization of this mycobacterium through molecular analysis of two captive sharks, a scalloped hammerhead Sphyrna lewini and a Japanese bullhead shark Heterodontus japonicus, exhibited in the same aquarium tank. We detected genital mycobacteriosis caused by M. marinum infection using molecular analyses, including polymerase chain reaction (PCR) and DNA sequencing targeting the 60 kDa heat-shock protein gene (hsp65), and peptide nucleic acid-fluorescence in situ hybridization (PNA-FISH) targeting the 16S rRNA gene. Both sharks showed granulomas in connective tissues of the gonads without central necrosis or surrounding fibrous capsules, which is unlike the typical mycobacterial granulomas seen in teleosts. This study reveals that elasmobranchs can be aquatic hosts of M. marinum. Because M. marinum is a representative waterborne NTM and a potential zoonotic agent, cautious and intensive research is needed to overcome a lack of data on the relationship between NTM and the aquatic environment in association with this subclass of Chondrichthyes.
  • Takeshi Komine, Hyogo Ihara, Kentaro Ono, Mitsumi Yoshida, Yuma Sugimoto, Mari Inohana, Hanako Fukano, Osamu Kurata, Shinpei Wada
    The Journal of veterinary medical science, 84(12) 1617-1620, Nov 18, 2022  
    In 2019, several aquarium-reared fish died at a sea life park in Japan. Necropsy revealed micronodules on the spleen in the dotted gizzard shad (Konosirus punctatus). Seven of 16 fish exhibited microscopic multifocal granulomas associated with acid-fast bacilli in the spleen, kidney, liver, alimentary tract, mesentery, gills, and/or heart. Bacterial cultures yielded isolates from the dotted gizzard shad and a Japanese sardine (Sardinops melanostictus). Microbiological and molecular biological examinations revealed the isolates as Mycobacterium pseudoshottsii. To our knowledge, this is the first isolation of M. pseudoshottsii from aquarium-reared fish.

Books and Other Publications

 5

Presentations

 108

Teaching Experience

 3

Research Projects

 16

Industrial Property Rights

 3