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Assessing the transmission risk of red sea bream iridovirus (RSIV) in environmental water: insights from fish farms and experimental settings

Aquatic animal viruses are considered to be transmitted via environmental water between fish farms. This study aimed to understand the actual transmission risk of red sea bream iridovirus (RSIV) through environmental water among fish farms. An environmental DNA (eDNA) method using iron-based floccul...

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Autores principales: Kawato, Yasuhiko, Takada, Yuzo, Mizuno, Kaori, Harakawa, Shogo, Yoshihara, Yusaku, Nakagawa, Yukihiro, Kurobe, Tomofumi, Kawakami, Hidemasa, Ito, Takafumi
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Society for Microbiology 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10580957/
https://www.ncbi.nlm.nih.gov/pubmed/37737592
http://dx.doi.org/10.1128/spectrum.01567-23
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author Kawato, Yasuhiko
Takada, Yuzo
Mizuno, Kaori
Harakawa, Shogo
Yoshihara, Yusaku
Nakagawa, Yukihiro
Kurobe, Tomofumi
Kawakami, Hidemasa
Ito, Takafumi
author_facet Kawato, Yasuhiko
Takada, Yuzo
Mizuno, Kaori
Harakawa, Shogo
Yoshihara, Yusaku
Nakagawa, Yukihiro
Kurobe, Tomofumi
Kawakami, Hidemasa
Ito, Takafumi
author_sort Kawato, Yasuhiko
collection PubMed
description Aquatic animal viruses are considered to be transmitted via environmental water between fish farms. This study aimed to understand the actual transmission risk of red sea bream iridovirus (RSIV) through environmental water among fish farms. An environmental DNA (eDNA) method using iron-based flocculation coupled with large-pore filtration was used to monitor RSIV DNA copies in seawater from fish farms and from an experimental infection model. RSIV dispersion in seawater from a net pen where the disease outbreak occurred was visualized by the inverse distance weighting method using multiple-sampling data sets from a fish farm. The analysis demonstrated that the center of the net pen had a high viral load, and RSIV seemed to be quickly diluted by the tidal current. To evaluate the transmission risk of RSIV in environmental water, the red sea bream Pagrus major (approximately 10 g) was exposed to RSIV-contained seawater (10(3), 10(4), 10(5), 10(6), and 10(7) copies/L) for 3 days, which mimicked field exposure. A probit analysis of the challenge test indicated that the inferred infection rates of seawater containing 10(5.9) copies/L and 10(3.1) copies/L of RSIV were 50% and 0.0001%, respectively. In the surveillance for 3 years at 10 fixed points (n = 306), there were only seven samples in which the viral load exceeded 10(4) copies/L in seawater. These results suggest that the transmission of RSIV among fish farms via seawater is highly associated with the distance between the net pens, and the environmental water is not always an infection source for the transmission of RSIV between fish farms. IMPORTANCE: Our surveillance of viral loads for red sea bream iridovirus (RSIV) by monitoring environmental DNA in fish farms suggested that the viral loads in the seawater were low, except for the net pens where RSIV outbreaks occurred. Furthermore, our experimental infection model indicated that the infection risk of RSIV-contained seawater with less than 10(3) copies/L was extremely low. The limited risk of environmental water for transmission of RSIV gives an insight that RSIV could be partly transmitted between fish farms due to the movement of equipment and/or humans from the fish farm where the disease outbreaks. Since our data suggest that seawater can function as a potential wall to reduce the transmission of RSIV, biosecurity management, such as disinfection of equipment associated with fish farms could be effective, even in the semi-open system aquaculture that the environmental water can be freely transferred, to reduce the risk of RSIV outbreaks.
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spelling pubmed-105809572023-10-18 Assessing the transmission risk of red sea bream iridovirus (RSIV) in environmental water: insights from fish farms and experimental settings Kawato, Yasuhiko Takada, Yuzo Mizuno, Kaori Harakawa, Shogo Yoshihara, Yusaku Nakagawa, Yukihiro Kurobe, Tomofumi Kawakami, Hidemasa Ito, Takafumi Microbiol Spectr Research Article Aquatic animal viruses are considered to be transmitted via environmental water between fish farms. This study aimed to understand the actual transmission risk of red sea bream iridovirus (RSIV) through environmental water among fish farms. An environmental DNA (eDNA) method using iron-based flocculation coupled with large-pore filtration was used to monitor RSIV DNA copies in seawater from fish farms and from an experimental infection model. RSIV dispersion in seawater from a net pen where the disease outbreak occurred was visualized by the inverse distance weighting method using multiple-sampling data sets from a fish farm. The analysis demonstrated that the center of the net pen had a high viral load, and RSIV seemed to be quickly diluted by the tidal current. To evaluate the transmission risk of RSIV in environmental water, the red sea bream Pagrus major (approximately 10 g) was exposed to RSIV-contained seawater (10(3), 10(4), 10(5), 10(6), and 10(7) copies/L) for 3 days, which mimicked field exposure. A probit analysis of the challenge test indicated that the inferred infection rates of seawater containing 10(5.9) copies/L and 10(3.1) copies/L of RSIV were 50% and 0.0001%, respectively. In the surveillance for 3 years at 10 fixed points (n = 306), there were only seven samples in which the viral load exceeded 10(4) copies/L in seawater. These results suggest that the transmission of RSIV among fish farms via seawater is highly associated with the distance between the net pens, and the environmental water is not always an infection source for the transmission of RSIV between fish farms. IMPORTANCE: Our surveillance of viral loads for red sea bream iridovirus (RSIV) by monitoring environmental DNA in fish farms suggested that the viral loads in the seawater were low, except for the net pens where RSIV outbreaks occurred. Furthermore, our experimental infection model indicated that the infection risk of RSIV-contained seawater with less than 10(3) copies/L was extremely low. The limited risk of environmental water for transmission of RSIV gives an insight that RSIV could be partly transmitted between fish farms due to the movement of equipment and/or humans from the fish farm where the disease outbreaks. Since our data suggest that seawater can function as a potential wall to reduce the transmission of RSIV, biosecurity management, such as disinfection of equipment associated with fish farms could be effective, even in the semi-open system aquaculture that the environmental water can be freely transferred, to reduce the risk of RSIV outbreaks. American Society for Microbiology 2023-09-22 /pmc/articles/PMC10580957/ /pubmed/37737592 http://dx.doi.org/10.1128/spectrum.01567-23 Text en Copyright © 2023 Kawato et al. https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0/) .
spellingShingle Research Article
Kawato, Yasuhiko
Takada, Yuzo
Mizuno, Kaori
Harakawa, Shogo
Yoshihara, Yusaku
Nakagawa, Yukihiro
Kurobe, Tomofumi
Kawakami, Hidemasa
Ito, Takafumi
Assessing the transmission risk of red sea bream iridovirus (RSIV) in environmental water: insights from fish farms and experimental settings
title Assessing the transmission risk of red sea bream iridovirus (RSIV) in environmental water: insights from fish farms and experimental settings
title_full Assessing the transmission risk of red sea bream iridovirus (RSIV) in environmental water: insights from fish farms and experimental settings
title_fullStr Assessing the transmission risk of red sea bream iridovirus (RSIV) in environmental water: insights from fish farms and experimental settings
title_full_unstemmed Assessing the transmission risk of red sea bream iridovirus (RSIV) in environmental water: insights from fish farms and experimental settings
title_short Assessing the transmission risk of red sea bream iridovirus (RSIV) in environmental water: insights from fish farms and experimental settings
title_sort assessing the transmission risk of red sea bream iridovirus (rsiv) in environmental water: insights from fish farms and experimental settings
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10580957/
https://www.ncbi.nlm.nih.gov/pubmed/37737592
http://dx.doi.org/10.1128/spectrum.01567-23
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