Experimental Reproduction of a Disease Causing Mass Mortality of Japanese Pearl Oyster Pinctada fucata martensii by Injection of Diseased Oyster Hemolymph.

Morizane, Tsuneo; Yamashita, Hirohumi; Fujita, Yoshiyuki; Kawakami, Hidemasa; Ochi, Osamu; Maeno, Yukio; Kamaishi, Takashi; Ito, Takafumi; Kurita, Jun; Nakajima, Kazuhiro; Ashida, Katsurou

doi:10.3147/jsfp.37.149

Cited by 6 publications

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“…Such PCR-positive individuals with a low a-value may have been infected with the spirochete even though the reddish-brown coloration had not yet progressed. It is not surprising that the PCR could be positive even for oysters with a low a-value, since individuals assigned a low a-value but displaying histopathological changes were reported in artificial infection experiments (Morizane et al, 2002;Nakayasu et al, 2004). In an infection test by transplantation of tissue pieces from diseased pearl oysters, there were no histological and color changes 1 month after transplantation, but death and reddish-brown coloration of the adductor muscle and histopathological changes were observed 2 months after infection (Kurokawa et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

“…Diseased pearl oysters exhibit reddish brown coloration of the adductor muscle and mantle (creamy white in healthy oysters) (Kurokawa et al, 1999;Miyazaki et al, 1999), and histopathological changes in diseased oysters were characterized by marked infiltration of hemocytes and the collapse of loose connective tissue (Kurokawa et al, 1999). AOD was demonstrated to be infectious by the transplantation of pieces of organs (Kurokawa et al, 1999;Nakayasu et al, 2004) and hemolymph (Morizane et al, 2002) from diseased pearl oysters to healthy pearl oysters. Although potential causes of AOD have been proposed (Miyazaki et al, 1999;S ugishita et al, 2005), the causative agent has not yet been identified.…”

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An Epidemiological Study of Akoya Oyster Disease Using Polymerase Chain Reaction Targeting Spirochaetes Genes

et al. 2018

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In a previous study, a member of Spirochaeta was presumed to cause Akoya oyster disease (AOD), and Candidatus Maribrachyspira akoyae was proposed as the putative causative agent. With the aim of performing an epidemiological study of AOD, polymerase chain reaction (PCR) assays were developed using the primers designed from shotgun metagenomic sequences identified as having high homology to Spirochaetes genes by a BLAST search. PCR assays with six primer sets produced specific target amplicons (n = 63-67) in pearl oysters collected from five AOD-endemic areas (n = 88), but did not in pearl oysters (n = 36) collected from three AOD-free areas. All individuals (n = 17) with the color index a-value above 3.0, which is an index of AOD development, were positive for all 6 primer sets in PCR. There was a positive correlation between the a-value and the results of PCR. These results show that the previous identification of Spirochaeta as an etiological agent of AOD is reasonable. Sequencing of amplification products confirmed only one nucleotide substitution in the PCR products, suggesting that the pathogenic causative agent of AOD has limited genetic diversity.

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An Epidemiological Study of Akoya Oyster Disease Using Polymerase Chain Reaction Targeting Spirochaetes Genes

et al. 2018

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“…However, since the histopathological changes appeared in the test oysters of the heart transplantation group, the mortality and a-values might have increased in this group if the experiment was continued for a longer period than 100 days. Morizane et al (2002) reported that the healthy pearl oysters inoculated with the hemocytes from dis eased pearl oysters developed the disease conditions and died. Thus, small quantities of the causative agent may exist in these tissues or cells of the affected pearl oysters.…”

Section: Discussionmentioning

confidence: 99%

“…Kurokawa et al (1999) reported that the disease condi tion of the mass mortality was reproduced by transplan tation of pieces of the mantle from diseased pearl oysters into healthy oysters or by cohabitation of dis eased and healthy oysters. Morizane et al (2002) showed that the disease causing mass mortality was reproduced experimentally in healthy pearl oysters by injection of hemolymph from affected oysters. These results suggest that the disease is caused by an infec tious agent.…”

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Tissue Distribution of the Agent of Akoya Oyster Disease in Japanese Pearl Oyster Pinctada fucata martensii

Nakayasu¹,

Aoki

Nakanishi

et al. 2004

Fish Pathol.

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ABSTRACT--Mass mortalities caused by akoya oyster disease have been occurring in cultured Japanese pearl oyster Pinctada fucata martensii in western Japan. Although the involvement of some causative agents was suggested, the cause of the disease is still unidentified. In this study, an experimental infection was performed by cohabitation of the diseased and healthy pearl oysters.A high mortality and characteristic disease conditions were observed in the test group. This result reconfirmed that this disease is caused by a certain infectious agent. To clarify the tissue distribution of the causative agent in diseased pearl oysters, two experimental infections were performed by transplantation of pieces of various tissues or injection of homogenates of vari ous tissues from diseased pearl oysters into healthy pearl oysters. The hemolymph, mantle and adductor muscle showed high infectious titers compared with those of the heart, digestive gland and hemocytes. The mantle had the highest infectious titer. Moreover, injection of the superna tant of a mantle homogenate also transmitted the disease to test pearl oysters. These results sug gest that the causative agent is concentrated in the mantle.

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“…The disease state observed in mass mortality events could be reproduced in healthy oysters following transplantation of pieces of the mantle from diseased pearl oysters into healthy oysters or through cohabitation with diseased oysters [ 6 ]. Injection of diseased oyster hemolymph also caused disease [ 8 ]. Thus, these mass mortality events were demonstrated to be due to infectious disease agent, and the disease was named Akoya oyster disease (AOD).…”

Section: Introductionmentioning

confidence: 99%

A Spirochaete is suggested as the causative agent of Akoya oyster disease by metagenomic analysis

et al. 2017

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Mass mortality that is acompanied by reddish browning of the soft tissues has been occurring in cultured pearl oyster, Pinctada fucata martensii. The disease is called Akoya oyster disease (AOD). Although spreading pattern of the disease and transmission experiments suggest that the disease is infectious, the causative agent has not yet been identified. We used shotgun and 16S rRNA-based metagenomic analysis to identify genes that are present specifically in affected oysters. The genes found only in diseased oysters were mostly bacterial origin, suggesting that the causative agent was a bacterial pathogen. This hypothesis was supported by the inhibition of AOD development in naïve oysters injected with the hemolymph of diseased animals followed immediately with penicillin bath-administration. Further analyses of the hemolymph and mantle specifically and universally detected genes of bacteria that belong to phylum Spirochaetes in diseased pearl oysters but not in healthy oysters. By in situ hybridization or immunostaining, a Brachyspira-like bacterium was observed in the smears of hemolymph from affected oysters, but not from healthy oysters. Phylogenetic analysis using 16S rRNA sequences showed that the presumptive causative bacterium was outside of but most closely related to family Brachyspiraceae. We propose ‘Candidatus Maribrachyspira akoyae’ gen. nov, sp nov., for this bacterium.

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Experimental Reproduction of a Disease Causing Mass Mortality of Japanese Pearl Oyster Pinctada fucata martensii by Injection of Diseased Oyster Hemolymph.

Cited by 6 publications

References 0 publications

An Epidemiological Study of Akoya Oyster Disease Using Polymerase Chain Reaction Targeting Spirochaetes Genes

An Epidemiological Study of Akoya Oyster Disease Using Polymerase Chain Reaction Targeting Spirochaetes Genes

Tissue Distribution of the Agent of Akoya Oyster Disease in Japanese Pearl Oyster Pinctada fucata martensii

A Spirochaete is suggested as the causative agent of Akoya oyster disease by metagenomic analysis

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