Koi herpesvirus (KHV) has infected farmed common carp in Poland clinically and asymptomatically since 2004. The role of non-carp species as vectors of virus transmission is well known except for in the case of KHV. The aim was to better understand this virus’ infection and transmission pathways in common carp, looking at the potential vector role of fishes kept with them. Eight species were experimentally infected with KHV by immersion in a suspension at 20°C ±1 and transferred to a tank after 45 minutes. Specimens were euthanised at intervals up to 56 days post infection (dpi) and tissue was examined for KHV DNA. Surviving infected fishes were introduced at intervals, each time into a separate tank, to naïve common carp for experimental infection. These were observed daily for symptoms, sacrificed along with controls after three months, and dissected to provide tissue samples. Also fish from 14 species collected from a farm with a history of KHV were sampled from 3 to 22 months after disease was confirmed. Organ sections from single fish were collected in a single tube. Viral DNA was detected in tench and roach samples up to 49 dpi, but in three-spined stickleback and stone maroko samples only up to 14 dpi. Transmission of KHV to naïve carp occurred after cohabitation. KHV DNA was detected in three fish species three months after the farm outbreak. We confirmed that grass and Prussian carp, tench, roach, and brown bullhead can transfer the virus to naïve common carp.

The aim of the study was to determine the transmission potential of carp edema virus (CEV) and koi herpesvirus (KHV) introduced to Europe by the invasive round goby (Neogobius melanostomus). A total of 70 round goby specimens were collected from the Szczecin Lagoon, Poland, and locations in Germany in the third and fourth quarters of 2018. The fish were analysed to detect KHV and CEV by PCR. Six fish specimens were positive for the presence of KHV, while none of the gobies examined showed the presence of CEV. The CEV genome was detected in the goby specimens from Germany and from Poland. Considering the high pace of the spread of the round goby and its effectiveness in acquisition of new ecological niches, it should be kept out during refilling of carp ponds. Further studies should focus on experimental cohabitation of CEV-infected round gobies and specific-pathogen-free (SPF) carp to investigate the potential for active virus transfer.

Cyprinid herpesvirus 3 (CyHV-3) is a virus infecting carp with disease symptoms of gill necrosis, fish discoloration, sunken eyes, and mortality reaching 90%. Several research groups have examined how to potentially abate the consequences of viral activity. Recently we showed that acyclovir inhibits CyHV-3 replication in vitro and in the present study we examined the anti-CyHV-3 activity of the tricyclic derivative of acyclovir 6-(4-MeOPh)-TACV (T-ACV), a fluorescent molecule known for higher lipophilicity than acyclovir, and therefore potentially better candidate for application in vivo. CCB and KF1 cell lines were incubated with T-ACV at concentrations of 0, 66.67, and 133.33 μM for three days and toxicity examined with MTT and CV assays. To investigate the antiviral activity of T-ACV, the lines were infected with CyHV-3 or mock infected and incubated for three days with the drug at concentrations of 0 or 66.67 μM. The activity of T-ACV was evaluated by plaque assay and TaqMan qPCR. T-ACV at a concentration of 66.67 μM displayed low toxicity and inhibited CyHV-3 activity by 13–29%, varying by cell line and method. The low anti-CyHV-3 activity of T-ACV indicates that it would be reasonable to screen several tricyclic derivatives of acyclovir for such activity.

Different concentrations of artemisia extract were experimentally tested to treat Lernaea and Argulus infestations in common carp (Cyprinus carpio) fish with different methods. A total number of 210 carps (50 ± 10 g) were collected from private farms at Kafr El-Sheikh Governorate, Egypt, and divided into 7-groups in triplicate: G1 negative-control (apparently healthy carps), G2 positive-control (infested carps with Lernaea and Argulus), G3: infested carps treated with dipping in a NaCl solution (5g /L for 5 min. for 3 consecutive days), G4-G5: infested carps treated with dipping in a solution of artemisia extract with concentration 50% and 60% respectively, for 5 minutes, then fishes were accommodated at a recovery tank and inspected for 10 min., G6-G7: infested carps were placed in aquarium supplied with artemisia extract (3 mg/ L and 6mg/L respectively, for 15 consecutive days). The results revealed that artemisia extract had a noticeable positive effect on survival, recovery of infested carps and the parasitic elimination% which increased proportionally with increasing the concentration of the extract, whereas the best results were obtained at G5. Also, there were an improvement in serum biochemical parameters (increased total protein, albumin and globulin with reduced AST, ALT, creatinine and urea), which were proportionally improved with increasing both concentration and the duration of exposure to the extract, (especially at G7). Gross and histopathological examination and alterations of skin, gills, liver and intestine also revealed a noticeable improvement to the normal in the groups treated with artemisia extract in comparison with G2 especially G6 and G7. Consequently, application of artemisia extract is a safe and optimal method for treatment of Argulus and Lernaea parasitism in cultured carp.

This work studied in vitro; the antibacterial activity of Vitex agnus-castus (VAC) extract against V. anguillarum, its minimal inhibitory and bactericidal concentrations (MIC and MBC) and detected its bioconstituents using gas chromatography-mass spectrometry (GC-MS) analysis besides evaluated its effect in vivo in carp either alone or combined with antibiotic to prevent or treat V. anguillarum infection. A total of 180 fish were divided into 6 groups; G1: negative-control, G2: V. anguillarum infected-control, G3: infected-(marbofloxacin (MAR) 10 mg/kg body weight), G4: infected-(VAC 1gm/kg ration), G5: infected-(VAC 1 gm/kg + MAR 10 mg/kg) all treatments lasted 7 days and G6: prophylactic treated-(VAC 1 gm/kg/30 day) then challenged. Results of scanning electron microscope revealed changes in bacterial morphology and loss of flagella by VAC where its MIC and MBC were 1.95 and 15.63 mg/ml respectively. Growth performance and survival rate improved in all treated groups in this descending order (G6, G4 then G5). All treatments significantly increased total protein, albumin, globulin, superoxide dismutase and decreased aspartate and alanine aminotransferases activities, malondialdehyde, urea and creatinine than G2 and mostly near to G1 in this ascending order (G3, G4 then G5). In G6, VAC protected carp from the infection and improved growth, survivability and most of blood parameters. MAR residue in fish musculature needed 4 days as a withdrawal period to be less than the maximum residue limits (MRL), while combination of VAC with MAR decreased it less than the MRL from the 1st day post treatment. Finally, VAC had a considerable antibacterial activity against V. anguillarum in both prevention and treatment assays. It can be used either alone or adding with MAR.

OBJECTIVE To determine in vivo effects of nitric oxide (NO) on blood-brain barrier (BBB) permeability in common carp (Cyprinus carpio L.). ANIMALS 148 carp. PROCEDURES Carp received glyceryl trinitrate (1 mg/kg) as an NO donor or received no treatment (control group). Nitrite and nitrate concentrations in carp sera were determined 0.25, 1, 3, 6, 8, 12, and 24 hours after treatment. In control and treatment groups, BBB permeability was analyzed by assessment of leakage of Evans blue dye into various brain areas at 6, 12, and 24 hours after glyceryl trinitrate treatment. Brain edema was determined by means of the wet-dry weight method and assessed with light microscopy on H&E-stained preparations of tissues obtained 6 and 24 hours after glyceryl trinitrate treatment. RESULTS Treatment with glyceryl trinitrate induced endogenous synthesis of NO, which was upregulated 6 and 8 hours after treatment. Increased NO synthesis was associated with increased permeability of the BBB, which developed 6 hours after treatment with the NO donor. Although the BBB became impermeable again by 12 hours after glycerol trinitrate treatment, brain edema still persisted 24 hours after treatment. CONCLUSIONS AND CLINICAL RELEVANCE In this study, treatment with an NO donor caused reversible opening of the BBB and brain edema in common carp. An intact BBB is important to prevent influx of potentially harmful substances into the brain. This investigation highlighted the possibility of BBB disarrangement caused by NO, a substance found in the CNS of all vertebrates evaluated.

Objective: To evaluate the effect of water temperature on intramuscular injected alfaxalone anesthesia in carp (Cyprinus carpio). Materials and Methods: Six healthy adult carp (C. carpio) were intramuscularly injected with alfaxalone (2.5, 5.0, or 7.5 mg/kg) at normal water temperature (25°C) and at low water temperature (2.5 mg/kg, 15°C). The respiratory rate, heart rate (HR), and anesthesia depth (AD) were evaluated every 5 min for 30 min after administration and every 1 h after 60 min after injection. Results: The respiratory and HRs did not change significantly upon alfaxalone injection, regardless of dose. However, a dose-dependent increase in AD scores was observed. Furthermore, 2.5 mg/kg alfaxalone injected in 15°C water showed an almost equal anesthetic effect to that of 5.0 mg/kg alfaxalone in 25°C water. Conclusion: Alfaxalone is readily available, and its anesthetic effect in carp was enhanced by lowering water temperature, illustrating the possibility of intramuscular injection of alfaxalone in fish. [J Adv Vet Anim Res 2024; 11(1.000): 27-32]