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Kumagai A.,Miyagi Prefecture Fisheries Technology Institute | Nawat A.,Miyagi Prefecture Fisheries Technology Institute Freshwater Fisheries Experimental Station
Fish Pathology | Year: 2011

We measured the concentration of F. psychrophilum in the ovarian fluid and milt of six species of salmonids that were collected from freshwater fish farms in Japan. We detected the bacteria in 39 of 61 groups of female fish (544 of 3,276 fish) and 21 of 42 groups of male fish (248 of 1,434 fish). The concentration of F. psychrophilum ranged from 10 to 10 7.7 CFU/mL (mean 10 2.0 CFU/mL) in the ovarian fluid and from 10 to 10 4.5 CFU/mL (mean 10 2.1 CFU/mL) in the milt. Our data suggest that the bacteria are widely distributed, and are present at high levels, throughout Japan © 2011 The Japanese Society of Fish Pathology. Source


Kumagai A.,Miyagi Prefecture Fisheries Technology Institute | Nawata A.,Miyagi Prefecture Fisheries Technology Institute Freshwater Fisheries Experimental Station
Fish Pathology | Year: 2011

We evaluated the occurrence of intra-ovum infection with Flavobacterium psychrophilum, the causative agent of bacterial cold-water disease (BCWD) and rainbow trout fry syndrome (RTFS), in the eggs of six salmonid species in Japan. Flavobacterium psychrophilum was isolated from four eggs in one of 13 lots of eyed eggs (999 eggs) imported from the United States. In contrast, the bacterium was not isolated from 28 lots (1,680 eggs) or 61 lots (3,693 eggs) of domestically produced unfertilized or eyed eggs, respectively. Our results indicate there is a low likelihood of intra-ovum infection in cultured salmonids in Japan © 2011 The Japanese Society of Fish Pathology. Source


Hirose E.,University of Ryukyus | Nozawa A.,Ehime University | Kumagai A.,Miyagi Prefecture Fisheries Technology Institute | Kitamura S.-I.,Ehime University
Diseases of Aquatic Organisms | Year: 2012

We used morphological and genetic analyses to investigate a pathogenic kinetoplastid isolated from a diseased edible ascidian Halocynthia roretzi with soft tunic syndrome. The morphological characteristics of the kinetoplastid are similar to those in the order Neobodonida in the subclass Metakinetoplastida. However, the presence of unique globular bodies distinguishes this kinetoplastid from the other polykinetoplastic genera (i.e. Cruzella, Dimastigella and Rhynchobodo) in this order. These globular bodies are cytoplasmic inclusions without an outer delimiting membrane and are composed of a homologous granular matrix containing electron-dense bands. A phylogenetic tree based on 18S rRNA gene sequences also indicated that the kinetoplastid belongs to the order Neobodonida, although it forms an independent clade in this order. From these results, we propose a new genus in the order Neobodonida, i.e. Azumiobodo gen. nov., and Azumiobodo hoyamushi as the type species for the genus. © Inter-Research 2012. Source


Kumagai A.,Miyagi Prefecture Fisheries Technology Institute Freshwater Fisheries | Ito H.,Miyagi Prefecture Fisheries Technology Institute | Sasaki R.,Miyagi Prefectural Fisheries Cooperative Association
Diseases of Aquatic Organisms | Year: 2013

The occurrence of soft tunic syndrome in wild populations of the ascidian Halocynthia roretzi was monitored by diving at 5 to 6 sites in Miyagi Prefecture in Japan in summer 2010 and 2011. These sites were located at varying distances from farming sites at which the disease had previously been detected. All dead ascidians were collected, and their tunics were examined for Azumiobodo hoyamushi, the causative agent of soft tunic syndrome, using 18S rRNA PCR. In both years, <1% of wild ascidians we observed (18 out of 2100 in 2010, and 30 out of 3100 in 2011) were dead. The flagellates were only detected in 8 out of 18 dead ascidians from 3 sites in 2010, and 4 out of 30 from 2 sites in 2011. Healthy ascidians were successfully experimentally infected with the disease by immersing tunic samples from diseased wild ascidians into the rearing water. When apparently healthy ascidians collected from the wild population were reared for 40 d using pathogen-free water, the tunics of some ascidians became softened. The flagellates were detected in these individuals, which were diagnosed with soft tunic syndrome. Our results suggest that soft tunic syndrome affects the wild population of ascidians in Japan. © Inter-Research 2013. Source


Kumagai A.,Miyagi Prefecture Fisheries Technology Institute | Kamaishi T.,Japan National Research Institute of Fisheries And Environment of Inland Sea
Fish Pathology | Year: 2013

PCR assays were developed for the rapid and sensitive detection of Azumiobodo hoyamushi, the protistan pathogen that causes soft tunic syndrome in the cultured ascidian Halocynthia roretzi. Two sets of A. hoyamushi-specific primers based on the 18S rRNA and b -tubulin gene sequences, respectively, of the flagellate were designed and validated for the detection of A. hoyamushi. In both PCR assays, the flagellate genes were detected in diseased ascidians, but not in apparently healthy ones. When DNA were extracted from flagellate suspensions obtained from infected tunics, the detection limits of the PCR assays using primers for the 18S rRNA and b -tubulin were 3.4 × 10 cells/mL and 3.4 × 102 cells/mL, respectively. Even at the early stage of infection when the slight clinical signs were observed only in the siphons, A. hoyamushi was detected from the affected tissue using 18S rRNA PCR, but not b -tubulin PCR. Thus, the 18S rRNA PCR is a rapid, sensitive and specific assay for diagnosing soft tunic syndrome. © 2013 The Japanese Society of Fish Pathology. Source

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