Infection Status of Ayu and Other Wild Fish with &lt;i&gt;Flavobacterium psychrophilum&lt;/i&gt; and &lt;i&gt;Edwardsiella ictaluri&lt;/i&gt; in the Tama River, Japan

Takeuchi, Hisato; Hiratsuka, Motoyuki; Oinuma, Hirotoshi; Umino, Yoshiyuki; Nakano, Daiki; Iwadare, Mayu; Tomono, Ryuji; Hori, Kazutomo; Imai, Toshihiro; Ishikawa, Takanori; Namba, Aki; Takai, Noriyuki; Ryuu, Takehiro; Maeda, Hiroshi; Nakai, Toshiko; Mano, Nobuhiro

doi:10.3147/jsfp.51.184

Cited by 16 publications

(14 citation statements)

References 24 publications

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“…In 2007 several mass mortalities were recorded in riverine ayu P. altivelis in Tokyo Metropolis, Hiroshima Prefecture, and Yamaguchi Prefecture, Japan; in each case, microbiological and pathological examinations accused E. ictaluri as the causative agent (Hassan et al, 2012; Hassan, Mahmoud, Dung, Yuasa, & Nakai, 2010; Mahmoud & Nakai, 2011; Nagai et al, 2008; Sakai et al, 2008; Sakai et al, 2009). These reports represent the first records of E. ictaluri infection of fish in Japan, with further subsequent outbreaks (Takeuchi et al, 2016).…”

Section: Introductionmentioning

confidence: 76%

Pathological and immunohistochemical studies following the experimental infection of ayu (Plecoglossus altivelis) by Edwardsiella ictaluri

Gaafar

Abdullah

Mahmoud

et al. 2020

Microscopy Res & Technique

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In recent decades, several mass mortalities were recorded in riverine ayu (Plecoglossus altivelis) in Tokyo Metropolis, Hiroshima Prefecture, and Yamaguchi Prefecture, Japan; in these outbreaks, microbiological and pathological examinations revealed Edwardsiella ictaluri as the causative agent. In this study, histopathological findings and immunohistochemical localization of the bacteria following experimental infection of ayu were discussed. Infection experiments were performed using 44 healthy cultured ayu fingerlings using E. ictaluri isolate (H90). The fish were injected with the isolate intraperitoneally with a dose of 5.1 × 105 cfu/fish, while the control fish were injected with sterile phosphate buffered saline. The fish were observed for clinical signs, with daily collection of dead fish, and isolation of bacteria from the posterior kidney was performed and confirmed to be E. ictaluri by slide agglutination using anti‐PH0744 serum. Daily collection of five moribund fish for necropsy and tissue specimens collection from hepatopancreas, spleen, posterior kidney, gills, brain, heart, and intestine for histopathological and immunohistochemical examination. Post‐mortem lesions were recorded as exophthalmia, bloody ascitis, hemorrhagic kidney and distended gallbladder, meningio‐encephalitis, hemorrhagic vent, and petechial hemorrhages on viscera. Histopathological examination revealed diffuse severe congestion in blood vessels and several degenerative and necrotic changes inconcurrent with positive antigenic staining by immunohistochemistry.

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Section: Introductionmentioning

confidence: 76%

Pathological and immunohistochemical studies following the experimental infection of ayu (Plecoglossus altivelis) by Edwardsiella ictaluri

Gaafar

Abdullah

Mahmoud

et al. 2020

Microscopy Res & Technique

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“…In a previous 2‐year (2011 and 2012) survey at four fixed sites established in main channel and a tributary of the Tama River, a typical urban river flowing through the Tokyo Metropolis, we observed mortality of ayu due to E. ictaluri infection only in the tributary site in late August of 2012 (Takeuchi et al., 2016). The fact that daily average water temperature (DAWT) of the tributary during this mortality period was approximately 10°C higher than in 2011 suggested that higher water temperature acted as a predisposing factor for E. ictaluri infection.…”

Section: Introductionmentioning

confidence: 84%

“…D and A from April to June in 2013–2015. All sampled ayu were transported on ice to the laboratory at Nihon University and distinguished as either cultured, released fish or wild fish by comparing the number of scales above the lateral line and otolith morphology, as described in the previous survey (Takeuchi et al., 2016).…”

Section: Methodsmentioning

confidence: 99%

“…However, such released fish are at risk of infections caused by pathogenic bacteria, namely, Vibrio anguillurum (Muroga & Motonobu, 1967), V. cholerae non‐O1 (Kiiyukia et al., 1992; Muroga et al., 1979), Aeromonas hydrophila (Jo & Onishi, 1980), A. veronii biovar sobria (Takeuchi et al., 2018), Flavobacterium psychrophilum (Iida & Mizokami, 1996) and Edwardsiella ictaluri (Sakai et al., 2008). Of these, recent frequent infections of riverine ayu with E. ictaluri as well as F. psychrophilum have attracted particular attention from both economic and public health viewpoints (Hassan et al., 2012; Miwa & Nakayasu, 2005; Takeuchi et al., 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Mortalities in wild populations of ayu due to E. ictaluri infection were first recorded in a few rivers in Japan from mid‐August to early October of 2007 (Sakai et al., 2008). Subsequently, although E. ictaluri had a high frequency of occurrence in apparently healthy ayu or other riverine fish species (Hassan et al., 2012; Takeuchi et al., 2016), there were no more mortality events of riverine ayu until 2012 (Takeuchi et al., 2016). Edwardsiella ictaluri isolates from Japanese fish species have extremely homogenous phenotypic and genetic characteristics and are pathogenic to ayu and other fish species (Hassan et al., 2012; Nagai et al., 2008; Sakai, Yuasa, Ozaki, et al., 2009; Takeuchi et al., 2019), suggesting that Japanese E. ictaluri is clonal with high pathogenicity and that many fish species inhabiting Japanese rivers are at risk of infection.…”

Section: Introductionmentioning

confidence: 99%

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Environmental factors affecting Edwardsiella ictaluri‐induced mortality of riverine ayu, Plecoglossus altivelis (Temminck & Schlegel)

Takeuchi

Hiratsuka

Hori

et al. 2021

Journal of Fish Diseases

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We analysed the predisposing factors for Edwardsiella ictaluri infection in the riverine ayu Plecoglossus altivelis on the basis of environmental and epidemiological data obtained in a tributary to and the lower reaches of the Tama River, Japan, in July and August 2011–2015. Mortality of ayu due to E. ictaluri infection was observed only in the tributary in August 2012 and 2013; both periods were unusually hot. During these mortality events, daily average water temperatures rose approximately 3–4°C over 4–8 days, reaching the optimum temperature for E. ictaluri infection (>25°C) and approaching the upper tolerable limit for ayu (30°C). Diurnal water temperature ranges (DWTRs) in the tributary during the mortality events exceeded 6°C, which was 1–2°C greater than in the lower reaches. Experimental infection of ayu with E. ictaluri resulted in higher mortality when exposed to 6°C DWTR than to 4°C DWTR. Furthermore, water levels in the tributary were generally low in August 2012 and 2013 because of low rainfall. From these results, we conclude that unusually high‐water temperatures combined with high DWTRs and low water levels drove riverine ayu mortality from E. ictaluri infection.

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Spatiotemporal distribution of Flavobacterium psychrophilum and ayu Plecoglossus altivelis in rivers revealed by environmental DNA analysis

Tenma¹,

Tsunekawa²,

Fujiyoshi³

et al. 2021

Fish Sci

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Outbreaks of bacterial cold-water disease (BCWD), caused by Flavobacterium psychrophilum, are widespread in Japan, especially among ayu Plecoglossus altivelis. There are few investigations of F. psychrophilum in river water, and its seasonal distribution has not been clarified. We aimed to identify the spatiotemporal dynamics of F. psychrophilum and ayu to provide information that is useful for establishing a countermeasure for BCWD. Quantitative analysis of environmental DNA (eDNA) was used to clarify the year-round dynamics of ayu and F. psychrophilum. We sampled river water from the Nagara and Ibi rivers in Japan, and conducted monthly water sampling and eDNA quantification. Changes in the eDNA concentration of ayu were consistent with the known life histories of the fish. There was a strong negative correlation between the eDNA concentration of F. psychrophilum and water temperature, suggesting a strong dependence of F. psychrophilum dynamics in the river on water temperature. Furthermore, relatively high eDNA concentrations were recorded for both organisms in early summer and fall, suggesting that ayu is infected with F. psychrophilum during these seasons when experiencing up- and downmigration, respectively.

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Infection Status of Ayu and Other Wild Fish with <i>Flavobacterium psychrophilum</i> and <i>Edwardsiella ictaluri</i> in the Tama River, Japan

Cited by 16 publications

References 24 publications

Pathological and immunohistochemical studies following the experimental infection of ayu (Plecoglossus altivelis) by Edwardsiella ictaluri

Pathological and immunohistochemical studies following the experimental infection of ayu (Plecoglossus altivelis) by Edwardsiella ictaluri

Environmental factors affecting Edwardsiella ictaluri‐induced mortality of riverine ayu, Plecoglossus altivelis (Temminck & Schlegel)

Spatiotemporal distribution of Flavobacterium psychrophilum and ayu Plecoglossus altivelis in rivers revealed by environmental DNA analysis

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