Koi herpesvirus and carp edema virus threaten common carp aquaculture in Croatia

Abstract

Common carp (Cyprinus carpio) is a very important fish species for warm‐water aquaculture in Croatia. All Croatian carp farms are subjected to a surveillance programme for the presence of koi herpesvirus (KHV), causing a deadly disease called koi herpesvirus disease (KHVD). However, there is no surveillance for other viral pathogens of importance like carp edema virus (CEV), a causative agent of koi sleepy disease (KSD). During regular testing within the KHVD surveillance programme, we tested samples for CEV simultaneously. The screening indicated possible outbreaks of KHVD and KSD. During 2016, KHVD broke out in an isolated area and soon thereafter a KHV eradication programme was successfully performed. However, during 2018 and 2019, two additional mortality events occurred in lakes in the southern part of Croatia during the spring. Samples from both events tested positive for CEV. An epidemiological investigation confirmed the introduction of infected carps from an infected farm to one of the lakes. To prevent the spreading of CEV into open waters, it is of utmost importance to introduce CEV testing before fish movement or to perform regular testing of all carp farms in the country to determine CEV prevalence for the purpose of implementation of control measures.

Carp edema virus and immune response in carp (Cyprinuscarpio): Current knowledge

“…Recently, Soliman et al (2019) presented new CEV sequences showing relatively low nucleotide identity with previously published isolates (43%-49%) and proposed the existence of a novel CEV genogroup III, also containing two older sequences by Ouyang et al (2018) and Ouyang et al (2020). On the contrary, additional investigation by Zrnčić et al (2020) showed that each sequence from the novel genogroup could be assigned to existing genogroups (I or II), when analysed in reverse complement form. Considering the possibility of the new sequences being uploaded in the reverse order, the existence of genogroup II as proposed by Soliman et al (2019), seems highly unlikely.…”

“…Before 2020, KSD/CEVD presence was reported in the following European countries: United Kingdom, Austria, Germany, Czech Republic, Slovakia, Hungary, Poland, Netherlands, France, Italy, Switzerland, Belgium, Serbia and Croatia (Adamek, Baska, et al, 2018;Bigarré & de Ploufragan-Plouzané, 2016;Haenen et al, 2013;Jung-Schroers et al, 2015;Lewisch et al, 2015;Matějíčková et al, n.d.;Matras et al, 2017;Pretto et al, 2015;Radosavljevic et al, 2018;Way et al, 2017;Zrnčić et al, 2020). Besides Japan, KSD/CEVD was confirmed in other Asian countries, namely India, Iraq, Republic of Korea, China and Thailand (Kim et al, 2018;Pikulkaew et al, 2020;Swaminathan et al, 2016;Toffan et al, 2020;Zhang et al, 2017).…”

“…However, few publications about mechanisms of CEV spread and its persistence in carp populations are available, although the possibility of cross-infection between common carp and koi has been confirmed (Adamek, Oschilewski, et al, 2017). TA B L E 1 Known CEV genogroups (Adamek, Baska, et al, 2018;Matějíčková et al, 2020;Matras et al, 2017;Ouyang et al, 2020;Swaminathan et al, 2016;Zrnčić et al, (BF-2) and Tilapia kidney 1 (TK-1), however without any success (Jung-Schroers et al, 2015;Lewisch et al, 2015;Oyamatsu, Hata, et al, 1997). Even tests of other forms of CEV cultivation based on using original gill cells or explants, which can be effectively used for CyHV-3 propagation, were unsuccessful (Adamek, El-Rahman, et al, 2019).…”

Carp edema virus‐related mortality in wild adult common carp (cyprinus carpio) in Italy

“…Although in the majority of sampling sites koi herpesvirus was confirmed as being the causative agent of death, in two locations CEV was identified as the only pathogen involved (Toffan et al., 2019). Similarly, mortality events occurred in lakes and ponds in Croatia in the period 2016–2019 and were associated with CEV detection (Zrnčić et al., 2020).…”

“…For a long time after these episodes, no other similar events were reported. The disease reappeared some years later, first in England (Way & Stone, 2013), followed by the Netherlands (Haenen et al., 2014), Austria (Lewisch et al., 2015), Brazil (Hesami et al., 2015), the Czech Republic (Vesely et al., 2015), Germany (Jung‐Schroers et al., 2015), Italy (Pretto et al., 2015), France (Bigarré et al., 2016), India (Swaminathan et al., 2016), China (Zhang et al., 2017), Hungary (Adamek et al., 2018), Poland (Matras et al., 2017), in the USA again (Padhi et al., 2019; Stevens et al., 2018), Korea (Kim et al., 2018), Iraq (Toffan et al., 2019), the Czech and Slovak Republic (Matějíčková et al., 2020) and Croatia (Zrnčić et al., 2020). In the majority of cases, farmed or traded common carp and koi were involved.…”