Do wild fish species contribute to the transmission of koi herpesvirus to carp in hatchery ponds?

Abstract

The koi herpesvirus (KHV) has spread worldwide since its discovery in 1998 and causes disease and mortality in koi and common carp populations with a high impact on the carp production industry. Many investigations have been conducted to examine ways of distribution and to identify possible transmission vectors. The answers, however, raise many new questions. In the present study, different wild fish species taken from carp ponds with a history of KHV infection were examined for their susceptibility to the virus. In the tissue of these fish, the virus load was determined and it was tested whether a release of the virus could be induced by stress and the virus then could be transferred to naive carp. Wild fish were gathered from carp ponds during acute outbreaks of virus-induced mortality in summer and from ponds stocked with carp carrying a latent KHV infection. From these ponds, wild fish were collected during the harvesting process in autumn or spring when the ponds were drained. We found that regardless of season, temperature variation, age and infection status of the carp stock, wild fish from carp ponds and its outlets could be tested positive for the KHV genome using real-time PCR with a low prevalence and virus load. Furthermore, virus transfer to naive carp was observed after a period of cohabitation. Cyprinid and non-cyprinid wild fish can therefore be considered as an epidemiological risk for pond carp farms.

First Report of Occurrences of Two Cyprinid Herpesvirus 3 Variants, I⁺⁺ II^− and I⁺⁺ II^+Δ, in China

“…Carassius auratus) may increase the difficulty in the detection of CyHV-3 during fish transfer and contribute for the distribution of the virus. (Eide et al, 2011;El-Matbouli and Soliman, 2011;Fabian et al, 2013;Reed et al, 2014). The first outbreak of koi herpesvirus disease in East Asian and Southeast Asian can be traced back to 1998 in Korea (Lee et al, 2012), 2002 in Indonesia (Sunarto et al, 2005) and 2003 in Japan (Sano et al, 2004).…”

Is There Any Species Specificity in Infections with Aquatic Animal Herpesviruses?–The Koi Herpesvirus (KHV): An Alloherpesvirus Model

“…Cyprinidae [23], but also in other fish families, e.g. acipenseridae [26] or percidae [26,27]. Earlier studies on KHV led [37] and [38] to conclude that KHVD cannot be transferred to fish other than C. carpio.…”

“…The fact that the disease has never been found within other fish than C. carpio, namely in common carp and koi, did not detract from the ------------1 21 st 29 -32 + -+ -----+ 2 -------28 28 -+ + 3 29 -30 + -+ 31 29 29 + + + 4 31 --+ --30 28 28 + + + 5 28 --+ ------- possibility of virus replication in other fish species and investigations were not conducted to investigate the role of KHVD transmission through vector fish species, i.e., its transfer as an infectious agent to naive carp detected by a combination of virological and serological methods other than in carp or koi [38]. It has since been found that a lot of other fish species such as goldfish, crucian carp, different sturgeon species, grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix) or tench (Tinca tinca) may be act as a healthy appearing carrier hosts which can transfer the KHV to naive carp or koi [22,24,26,27,39]. KHVD has never occurred in any of those fish species when inoculated with KHV.…”

“…For CyHV-3 or koi herpesvirus (KHV), although KHV disease (KHVD) is induced only in the species C. carpio (common carp and koi), it has been demonstrated that this virus can be present, and sometimes replicated, in a lot different fish species living in fresh and brackish water. KHV DNA has been identified by different PCR methods in a lot of members of the families Acipenseridae [22], Cyprinidae, including common carp or koi hybrids [23][24][25], and Percidae in many wild fish populations within close vicinity to, or in carp ponds [26,27]. Furthermore KHV has also been detected in fresh water mussels and crustaceans [28].…”

Susceptibility of stone loach (Barbatula barbatula) and hybrids between sterlet (Acipenser ruthenus) and beluga (Huso huso) to cyprinid herpesvirus 3

“…goldfish (Carassius auratus) Bergmann et al 2010;El-Matbouli and Soliman 2011;Radosavljevic et al 2012), grass carp (Ctenopharyngodon idella) ), silver carp (Hypophthalmichthys molitrix) (Kempter et al 2012;Radosavljevic et al 2012), common bream (Abramis brama) (Kempter et al 2012), tench (Tinca tinca) (Fabian et al 2012;Kempter et al 2012;Radosavljevic et al 2012), some non-cyprinid species such as ruffe (Gymnocephalus cernua), spined loach (Cobitis taenia) (Kempter et al 2012), European perch (Perca fluviatilis) (Fabian et al 2012;Kempter et al 2012), and even Atlantic sturgeon (Acipenser oxyrinchus) ). Some fishes were even able to transmit CyHV-3 to naïve common carp, for example goldfish (Bergmann et al 2010;El-Matbouli et al 2011;Radosavljevic et al 2012), grass carp, silver carp (Kempter et al 2012;Radosavljevic et al 2012), common bream (Kempter et al 2012), tench (Fabian et al 2012;Kempter et al 2012;Radosavljevic et al 2012), ruffe (Kempter et al 2012) and European perch (Kempter et al 2012). For this reason, it is necessary to verify susceptibility to CyHV-3, as well as determining species which can act as carriers for susceptible species.…”