Redspotted Grouper Nervous Necrosis Virus and the Reassortant RGNNV/SJNNV In Vitro Susceptibility against a Commercial Peroxy-Acid Biocide under Different Conditions of Use

Aquaculture is a constantly growing sector. The intensification of fish production and the movement of aquatic animals could cause the spread of infectious diseases. Remarkably, the diffusion of viral agents represents the major bottleneck for finfish production, and viral encephalopathy and retinopathy (VER) is considered the most impacting disease for Mediterranean aquaculture. No effective therapies are available to contrast VER, and vaccination can be applied only in grow-out facilities. Hence, programs to minimize the sanitary risks in farms are paramount to implementing hygienic standards and biosecurity. This study aimed to evaluate the in vitro virucidal activity of a peroxy-acid disinfectant (Virkon® S, DuPont, Sudbury, UK) towards the two NNV strains most widespread in the Mediterranean Sea. Remarkably, two protocols were applied to assess the virucidal activity under different conditions of use: the suspension test and the net test. The latter has been applied to evaluate the efficacy of the biocide on instruments, simulating the infield application. The obtained results demonstrated the suitability of the tested biocide for NNV inactivation, being effective under some of the tested conditions. However, the presence of organic matter, the concentration of the product, and the application conditions can significantly affect the result of the disinfection procedure

Swim Bladder Disorders in Koi Carp (Cyprinus carpio)

Swim bladder disorders and consequent buoyancy problems are encountered in ornamental fish, including koi carp. Nevertheless, beyond clinical and pharmacologicalmanagement, they are largely underdiagnosed. In this study, nine koi carp showing abdominal swelling and abnormal swimming behavior were investigated. Clinical approach, varying from case to case, included ultrasonographic and X-ray investigations, bacteriological analysis of the collected fluid, antimicrobial susceptibility pattern, and possibly histological analysis. Diagnostic imaging, corroborating gross examination, documented swim bladder deformation/dislocation and serous fluid within the swim bladder chambers of most animals. Bacteria belonging to the Aeromonas hydrophila/caviae group and Shewanella xiamenensis were identified. S. xiamenensis strains showed a sensibility to all tested molecules except for one strain, which was resistant to tetracycline and cyprofloxacin. Antibiotic treatment succeeded in the full recovery of three cases in which S. xiamemensis infection was detected. Chronic aerocystitis was histologically documented where tissue was available. The swim bladder histopathological findings highlighted a chronic process that had compromised the quality of life of the animals. A multidisciplinary clinical\u2013pathological and microbiological approach is highly suggested to recognize swim bladder conditions as early as possible, aiming to drive medical intervention and raising the chances of fish survival

Redspotted Grouper Nervous Necrosis Virus and the Reassortant RGNNV/SJNNV In Vitro Susceptibility against a Commercial Peroxy-Acid Biocide under Different Conditions of Use

Aquaculture is a constantly growing sector. The intensification of fish production and the movement of aquatic animals could cause the spread of infectious diseases. Remarkably, the diffusion of viral agents represents the major bottleneck for finfish production, and viral encephalopathy and retinopathy (VER) is considered the most impacting disease for Mediterranean aquaculture. No effective therapies are available to contrast VER, and vaccination can be applied only in grow-out facilities. Hence, programs to minimize the sanitary risks in farms are paramount to implementing hygienic standards and biosecurity. This study aimed to evaluate the in vitro virucidal activity of a peroxy-acid disinfectant (Virkon® S, DuPont, Sudbury, UK) towards the two NNV strains most widespread in the Mediterranean Sea. Remarkably, two protocols were applied to assess the virucidal activity under different conditions of use: the suspension test and the net test. The latter has been applied to evaluate the efficacy of the biocide on instruments, simulating the in-field application. The obtained results demonstrated the suitability of the tested biocide for NNV inactivation, being effective under some of the tested conditions. However, the presence of organic matter, the concentration of the product, and the application conditions can significantly affect the result of the disinfection procedure

Isolation of Clostridium perfringens from starving juvenile sturgeons with severe enteritis

In November 2020, a mortality episode in juvenile sturgeons occurred in a hatchery in Northern Italy, associated with severe abdomen dilatation and peculiar behavioral alteration, characterized by upside-down surface swimming. Juveniles (4-5 months old, average weight ± 25g) of Siberian and Russian sturgeons (Acipenser baerii and A. gueldenstaedtii) and hybrid sturgeons GUBA (A. gueldenstaedtii x A. baerii), were promiscuously maintained in concrete hatchery tanks supplied by well water (15 °C, O₂ 7 ppm, CO₂ 12 ppm), and fed at 0.4% of body weight per day. The outbreak resulted in cumulative mortality of 25%. Thirty moribund sturgeons were collected, euthanized with an overdose of MS-222, and underwent necropsy followed by histological, bacteriological, and virological investigations. Main macroscopic findings included diffuse and severe bloating of gastrointestinal tracts due to foamy contents, with severe thinning and stretching of the intestinal wall, absence of visceral fat, and small size of the hepatopancreas. Histology revealed variable degrees of attenuation, sloughing, and necrosis of the intestinal epithelium, associated with bacterial aggregates, and hepatocellular degeneration. All specimens were negative for Herpesviruses by WSSK-1 cell culture, and Iridovirus (AcIV-E) and Betanodavirus by molecular methods. Bacteriological examination revealed Plesiomonas shigelloides and Cetobacterium somerae in a subset of intestines, while other organs yielded negative results. Based on recent literature, an intestinal dysmicrobism was suspected, and anaerobic gram+ bacteria were investigated. Clostridium perfringens was isolated from the intestines, and specific PCRs identified the toxinotype A and the β2 toxin gene. The quantity of food was raised to 1.5% of body weight, and after 5 days the abnormal behavior and mortality ceased. The analyses were repeated after 12 weeks from the food increase and showed no alterations including negative results for C. perfringens isolation. Therefore, we hypothesize that underfeeding may have led to an imbalance in intestinal microbiota, favoring the C. perfringens infection, which was successfully controlled through management improvement. The importance of intestinal microbiota in sturgeons, of which the genera Clostridium is one of the main components, has recently been highlighted and, although this will need further validation, the increased diet in this case was successful and possibly restored the microbiota