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Catch and consumption of torpedo scad (Megalaspis cordyla) over the western Indian Ocean, but also the western Pacific from Japan to Australia is constantly increasing. Taking into account the degree of exploitation and missing information on the population structure of torpedo scad stocks it is crucial to provide population data. The analysis included individuals obtained in 2012 and 2013 from local markets in Madagascar, Tanzania, Vietnam and Cambodia and after successful DNA extraction fragment of the nuclear rhodopsin gene (RH1) and 9 microsatellite regions (SSRs) were amplified and analysed. Based on the obtained results it was found that there was no 100% overlap between the compared RH1 sequences and those from GenBank. In the case of the studied SSRs, the results allowed the initial characterisation and assessment of the genetic diversity of populations. Moreover, population assignment test distinguished the studied populations into two geographically distant subpopulations.

Koi herpesvirus (KHV) causes a highly infectious disease afflicting common carp and koi, Cyprinus carpio L. Various molecular and antibody-based detection methods have been used to elucidate the rapid attachment and dissemination of the virus throughout carp tissues, facilitating ongoing development of effective diagnostic approaches. In situ hybridization (ISH) was used here to determine the target tissues of KHV during very early infection, after infecting carp with a highly virulent KHV isolate. Analysis of paraffin-embedded tissues (i.e. gills, skin, spleen, kidney, gut, liver and brain) during the first 8 h and following 10 days post-infection (hpi; dpi) revealed positive signals in skin mucus, gills and gut sections after only 1 hpi. Respiratory epithelial cells were positive as early as 2 hpi. Viral DNA was also detected within blood vessels of various tissues early in the infection. Notable increases in signal abundance were observed in the gills and kidney between 5 and 10 dpi, and viral DNA was detected in all tissues except brain. This study suggests that the gills and gut play an important role in the early pathogenesis of this Alloherpesvirus, in addition to skin, and demonstrates ISH as a useful diagnostic tool for confirmation of acutely infected carp.

Hygienic measures such as disinfection are important tools for the maintenance of fish health in aquaculture. While little information is available on the disinfection of water intended for fish containment, Huwa-San®, a disinfectant used in food and water industries, was used for daily treatment at concentrations of approximately 60 ppm over a total period of 3 months (experiment 1) with a 3-week treatment-free interval after 2 months (experiment 2). During this period, koi herpesvirus (KHV) was added to the water of two aquaria, one used as a normal contact control, the other one receiving daily water disinfectant treatments that prevented KHV infection of carp. In the second experiment, Huwa-San® treatment was interrupted and KHV infection was prevalent. However, when naive fish were introduced to the same aquarium after re-application of disinfectant, KHV could not be detected in those naive fish. Whilst KHV could not be detected in samples where disinfectant had been applied, it was present in samples of naive fish cohabiting with infection contact control animals which had undergone no disinfectant treatment over experiments 1 and 2. The results presented here show that water treatment with a disinfectant may prevent transmission of infectious KHV to naive carp cohabited with infected carp.

Hybrids of koi, Cyprinus carpio x crucian carp, Carassius carassius and koi x goldfish, Carassius auratus, proved to be susceptible to koi herpesvirus (KHV, syn. CyHV-3) and developed KHV disease (KHVD). While hybrids of koi x goldfish were partly resistant to mortality following infection by immersion, most koi x crucian carp hybrids died after bath infection. KHV DNA was detected in dead fish but also in all surviving animals by different polymerase chain reactions (PCRs). According to these results, hybrid crossbreeding does not seem to prevent severe losses associated with KHV in terms of inducing KHVD. The present study showed severe losses after a waterborne KHV infection of between 35% and 100% in koi x goldfish and koi x crucian carp hybrids as well as in SPF carp.

Previous and new PCRs for KHV detection were compared by estimation of their sensitivity in recognizing KHV DNA in plasmids, cell culture extracted KHV DNA and total DNA obtained from field tissue samples. A modified real-time PCR (Gilad et al., 2004), combined with an internal control system (IC2, Hoffmann et al., 2006) in a duplex assay, was used as a “gold standard”. The lowest reliably determined virus concentration between, 5 and 10 KHV DNA genomic equivalents, was found by real-time PCR (Gilad et al., 2004), nested PCR (Bergmann et al., 2006) and one-tube semi-nested PCR. All other published and unpublished PCRs, as well as the commercial Loopamp®, recognized KHV DNA at higher concentrations only. Additionally, KHV variants, newly adapted to European conditions, which could not be detected by PCR according to Bercovier et al. (2005) were found in two field samples from carp and koi from different regions of Germany. A negative influence of sample pooling was shown with field samples tested by real-time PCR.

Parasitic copepods of the genus Achtheres commonly infect perch, Perca fluviatilis, and zander, Sander lucioperca, in Europe. The aim of this study was to verify the specific identity of these copepods. The parasites were examined morphologically, biometrically and genetically. Statistical processing of the biometrical data was based on both empirical measurements and transformed data related to total length and genital trunk width. Principal component analysis was applied to both sets of data. DNA of both parasite 'forms' was amplified using two sets of primers (EU5.8S+EU18S and 18SF1+28SR) and the products were subjected to restriction fragment length polymorphism (RFLP). Morphological differences were found in the overall shape of the copepod bodies as well as in the details of the armament of some appendages. The morphometric study emphasized the importance of second maxillae and genital process as the variables most distinctly distinguishing the two 'forms'. The two 'forms' of Achtheres differed in the DNA sequence amplified by one set of primers. RFLP revealed even more extensive differences between these two copepods. We concluded that the copepods parasitizing perch should be referred to as Achtheres percarum von Nordmann, 1832, whereas a long-forgotten name, A. sandrae Gadd, 1901, should be applied to the copepods from zander.