Author: marina02

Decay of Infectious Salmon Anemia Virus (ISAV) infectivity in raw seawater

Infectious salmon anaemia virus (ISAV), a single-stranded, enveloped RNA virus of the Orthomyxoviridae family, poses a significant challenge to salmon aquaculture in Norway. Accurately determining ISAV decay rates under different seawater conditions is crucial for improving disease-prevention and management strategies. Previous studies have reported that ISAV decay in seawater can range from less than 3 hours to 112 days. In this current study, we used a salmon fry challenge model to monitor the decline in ISAV infectivity over time in seawater at different temperatures and water conditions. Cell line-propagated ISAV was inoculated into 200 mL of raw seawater of 34 ppt held at different temperatures (4, 7, 10, 13, and 17°C) incubated for up to 20 days. Similarly, ISAV was inoculated into 200 ml seawater from a salmon recirculatory aquaculture system (RAS) with high organic contents and incubated at 10°C. Following incubation, the virus-containing seawater was added to separate tanks containing 200 mL of fresh water with 30 salmon fry each. Fish were bath-challenged with the virus for 4 hours under aeration. After 90-degree days, all fish were sampled, and virus load was determined using RT-qPCR. Infection prevalence showed an inverse relation with increasing seawater temperature, organic content and incubation time. The experimental data were fitted to a temperature-dependent exponential decay model, and half-lives of viral infectivity were estimated. Using logistical regression, we derived an equation that describes the temperature-dependence of infectivity half-lives between 4°C and 17°C. These temperature-specific half-life estimates were incorporated into a Lagrangian Advection and Diffusion Model (LADiM) to simulate disease spread scenarios. More accurate estimates of virus survival across different environmental conditions will enhance the reliability of virus dispersal models and support more effective strategies for disease control and risk mitigation.

1. Kannimuthu, Dhamotharan, HAVFORSKNINGSINSTITUTTET, Presenter
2. Roh, HyeongJin, HAVFORSKNINGSINSTITUTTET, Author
3. Morton, H. Craig, HAVFORSKNINGSINSTITUTTET, Author
4. Skaftnesmo, Kai Ove, HAVFORSKNINGSINSTITUTTET, Author
5. D. Peñaranda, Ma. Michelle, HAVFORSKNINGSINSTITUTTET, Author
6. Frøysa, Håvard Guldbrandsen, HAVFORSKNINGSINSTITUTTET, Author
7. Sævik, Pål Næverlid, HAVFORSKNINGSINSTITUTTET, Author
8. Grove, Søren, HAVFORSKNINGSINSTITUTTET, Author

Evolution of an Extended Pathogenicity Motif in VP2 of Infectious Pancreatic Necrosis Virus Isolates from Farmed Rainbow Trout in Turkey

Introduction: Infectious pancreatic necrosis virus (IPNV) causes economic losses with highly variable mortality rates, especially in rainbow trout worldwide. The virus has a double-stranded bi-partite RNA genome designated segment A, and B. VP2 is the major capsid protein and contains a central variable domain and antigenic site (residues 183-335) and two hypervariable regions (residues 239-257 and 271-284). The central variable region includes a pathogenicity locus at positions 217 and 221 (PT persistent, PA, low virulent, TA virulent). In this study, we determined the whole genome of 9 Turkish IPNV isolates by NGS. The overall analysis, including all IPNV sequences published from Turkey, indicates the emergence of IPNV isolates signified by previously described extended pathogenicity locus since 2007. Methodology: New complete genome sequences of nine rainbow trout isolates from Turkey were determined and a time-dependent change of the extended pathogenicity motif of VP2 from P217 T221 A247 (PTA) to PTE P217 T221 E247 over a period of 10 years was identified. Results: As a result of the whole genome analyses of nine isolates of Turkey, the isolates were identified as genotype 5 (serotype SP). A wider analysis of 99 IPNV sequences from Turkey and Iran revealed the emergence of the motif PTE from 2007 to 2017 inducing significant morbidity in fry by 2013. Conclusion: This study focused on nine additional IPNV isolates from Turkey and complemented the existing IPNV sequence dataset, now allowing to describe the gradual emergence of the PTE motif in IPNV isolates from 2007-2017. This is evident from the network analysis which suggests two independent transmission chains inside Turkey after the PTE motif evolved in 2007. In fact a displacement of the PTA carrying by PTE carrying IPNV isolates appears to be connected to a production peak of rainbow trout in 2013. It additionally confirms that IPNV carrying the PTE motif was introduced to Iran from Turkey. An additional CAI analysis provided more evidence indicating that rainbow trout culture in Turkey has an influence on the evolution of IPNV.

1. KURUCAY, HANNE NUR, ONDOKUZ MAYIS UNIVERSITY, Presenter
2. TAMER, CUNEYT, ONDOKUZ MAYIS UNİ, Author
3. Ulrich, Kristina, Institute of Aquaculture, University of Stirling, Scotland FK9 4, Author
4. Di Paola, Nicholas, Center for Genome Sciences, US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702-5011, U, Author
5. ALBAYRAK, HARUN, ONDOKUZ MAYIS UNİ, Author
6. Weidmann, Manfred, Medizinische Hochschule Brandenburg Theodor Fontane, 01968 Senftenberg, Germany, Author

Viral Nervous Necrosis outbreak affecting different grouper species in the Azorean archipelago

Introduction

The Azorean archipelago is located in the central Atlantic Ocean along the Mid-Atlantic Ridge. The Azores Current maintains and favours high biodiversity and the largest marine protected area network in Europe has been established around the archipelago to safeguard the ecosystem. Groupers in the Azores are of high ecological and economic significance, typically found around rocky reefs up to 200m. The dusky grouper (Epinephelus marginatus) is the most emblematic and extensively studied species in the region. Its slow growth and long lifespan, coupled with traits like late sexual maturity and strong site fidelity, make it particularly vulnerable to anthropogenic and environmental impacts. To mitigate these risks, the Azores have implemented strict management measures, including seasonal fishing bans and gear restrictions. In the summer 2024, a relevant and persistent marine heat wave caused an increase in the sea surface temperature with several reports of moribund or stranded groupers across the western and central island groups of the Azorean archipelago.

Methodology

Approximately 100 animals were reported to local authorities, and 40 grouper specimens were collected from fishermen from different islands and frozen until processing. Based on clinical signs and anamnestic informations, a suspicion of Viral Nervous Necrosis (VNN) was raised. Brain and eye were sent frozen or fixed in RNAlater for detection of NNV RT-qPCR. In addition, where possible, portion of main internal organs were fixed in 10% neutral buffered formalin and shipped for histological and immunohistochemical analysis.

Results

All sampled brains tested positive for NNV by qRT-PCR and confirmed in some cases by virus isolation. Species affected include dusky grouper and island grouper (Mycteroperca fusca). Based on phylogenetic analysis of the obtained sequences clustered together inside the RGNNV species. The high similarity shared by the obtained sequences, regardless the species or the island of origin, suggests a single introduction of the pathogen, probably happened in recent time. Immunohistochemistry performed on selected samples confirmed the presence of immunoprecipitates in the brain and retina. No other obvious lesions were observed by histology in visceral organs and other infectious diseases were then excluded.

Conclusions

This is the first report of VNN in the Azorean Archipelago and the first at such a high latitude in the Atlantic Ocean. Warming of water temperature may have created conditions that favours the occurrence and spread of VNN. Epidemiological investigations are currently on-going to develop hypothesis regarding the potential pathways for the introduction of NNV to the area.

1. TOFFAN, ANNA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DELLE VENEZIE, Presenter
2. MARSELLA, ANDREA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DELLE VENEZIE, Author
3. ABBADI, MIRIAM, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DELLE VENEZIE, Author
4. PRETTO, TOBIA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DELLE VENEZIE, Author
5. SILVA, L., INSTITUTO DO MAR (IMAR) AND INSTITUTE OF MARINE SCIENCES – OKEANOS, UNIVERSITY OF THE AZORES, HORTA, FAIAL, PORTUGAL, Author
6. ROSA, J., INSTITUTO DO MAR (IMAR) AND INSTITUTE OF MARINE SCIENCES – OKEANOS, UNIVERSITY OF THE AZORES, HORTA, FAIAL, PORTUGAL, Author
7. NOVOA-PABONn A., A., INSTITUTO DO MAR (IMAR) AND INSTITUTE OF MARINE SCIENCES – OKEANOS, UNIVERSITY OF THE AZORES, HORTA, FAIAL, PORTUGAL, Author
8. GOMES, INES, INSTITUTO DO MAR (IMAR) AND INSTITUTE OF MARINE SCIENCES – OKEANOS, UNIVERSITY OF THE AZORES, HORTA, FAIAL, PORTUGAL, Author
9. AFONSO, PEDRO, INSTITUTO DO MAR (IMAR) AND INSTITUTE OF MARINE SCIENCES – OKEANOS, UNIVERSITY OF THE AZORES, HORTA, FAIAL, PORTUGAL, Author

Betanodavirus infection in mullet (Mugil cephalus) in Mediterranean Sea, Italy

The flathead grey mullet (Mugil cephalus) is a promising species for sustainable aquaculture, thanks to its biological characteristics such as fast growth, low dietary requirements, and adaptability to a wide range of breeding systems. However, Italian farming is still based mainly on extensive systems to rear juveniles obtained from the wild. Furthermore, interest is rising in traditional products obtained from adult female mullet, such as “bottarga,” putting them at risk of overfishing. In the framework of a collaboration between the International Marine Centre and the University of Bologna, spawning and rearing protocols were set up using wild broodstock. However, due to a low survival rate in some reproductive seasons, some health problems, in addition to technical issues, were suspected. Betanodavirus infection has already been reported in some Mugilidae, including M. cephalus in association with asymptomatic fish as well as during epizootics across several countries (Italy, Israel, and Korea).
As one out of two wild females used as broodstock in 2023 tested positive for Betanodavirus, a retrospective analysis was conducted to investigate Betanodavirus presence in mullet eggs/larvae/juveniles obtained during five breeding seasons (2019-2023). Betanodavirus presence was associated with high mortality in larvae obtained during the 2021 breeding season, but not in previous and, most importantly, not in the following year’s seasons, suggesting an origin of the virus exogenous to the hatchery system. However, to further investigate viral circulation in farming systems hosting mullets reared in captivity, live feed (rotifers, artemia) and a representative sampling of juveniles obtained from the 2022 season (n=30) and adults obtained from the 2019 season (n=40) were screened for Betanodavirus presence. No virus was detected in specimens from the rearing systems, suggesting that the most probable origin of the virus was wild broodstock. To further investigate Betanodavirus presence in wild fish populations, a survey is ongoing on wild mullets and European seabass (n=135) sampled from April 2024 to April 2025 in Cabras Lagoon (Sardinia, Italy).
Despite the ascertained presence of Betanodavirus in wild broodstock, the investigations conducted so far show that the reared populations (2019, 2022) are free from Betanodavirus infection, making them an ideal candidate as future broodstock to close the life cycle under captive conditions. This achievement could significantly contribute to controlling health problems associated with pathogens circulating in wild populations, thus improving rearing conditions and accordingly increasing the sustainability of aquaculture and counteracting the impact of overfishing.

1. Ciulli, Sara, Department of Veterinary Medical Sciences, University of Bologna, Cesenatico, Italy, Presenter
2. Loi, Barbara, International Marine Centre – IMC Foundation, Oristano, Italy, Author
3. Errani, Francesca, Department of Veterinary Medical Sciences, University of Bologna, Cesenatico, Italy, Author
4. Vallainc, Dario, International Marine Centre – IMC Foundation, Oristano, Italy, Author
5. Bezzi, Claudia, Department of Veterinary Medical Sciences, University of Bologna, Cesenatico, Italy, Author
6. Concu, Danilo, International Marine Centre – IMC Foundation, Oristano, Italy, Author
7. Carboni, Stefano, International Marine Centre – IMC Foundation, Oristano, Italy, Author
8. Volpe, Enrico, Department of Veterinary Medical Sciences, University of Bologna, Cesenatico, Italy, Author

Early juvenile ayu can survive in Plecoglossus altivelis poxvirus infection and acquire immunity

Atypical cellular gill disease (ACGD) in ayu Plecoglossus altivelis caused by P. altivelis poxvirus (PaPV) infection has led to significant economic losses in aquaculture. Ayu is an amphidromous fish with a one-year life cycle. It is known from experience that ACGD has not occurred in aquaculture farms using wild-caught juveniles as seedlings, and a previous paper reported ayu ranging from 0.39g to 0.83g caught near shore or river mouth were positive in PaPV PCR without any symptoms. These imply that wild early juvenile fish have acquired immunity to ACGD. In this study, we examined the mortality of early juveniles experimentally infected with PaPV and immunity against subsequent PaPV infection.

A virus solution was prepared from the homogenate gills of spontaneously ACGD-dead ayu. Ayu (0.5g) were challenged by immersion in rearing water added with the virus solution for the infected group (I) or MEM for the non-infected group (N). The fish were kept at 18℃ for 3 weeks and at 25℃ for about 4 months. Subsequently, the fish (6.2g) were challenged with virus solution (I) or MEM (N), and kept at 18℃ for 3 weeks. The gills were periodically sampled for the quantification of virus DNA copy number, histopathology, and gene expression analysis after infection.

The survival rates were 100% and 97.0% in the non-infected and infected group, respectively after the primary infection. Both the infected and non-infected groups were negative in PaPV PCR 5 months after infection. The secondary challenge test showed survival rates of 100%, 92.9%, 0%, and 100% in the group of N-N, I-N, N-I, and I-I, respectively. Virus DNA copies were at the same level in both N-I and I-I groups up to the middle stage of infection, and those in N-I group increased more than I-I group in the following period of infection. Histopathological examination of the gills showed the occurrence of atypical cells in the secondary lamella in N-I group. The expression level of IFN-γ in the gills was upregulated in I-I group at the early stage of infection.

These results suggest the mortality of early juvenile ayu by PaPV infection is quite low, and the surviving fish can acquire immunity against a subsequent infection. In addition, immunity in surviving fish may involve a cell-mediated response, preventing the virus propagation and consequently the development of ACGD symptoms at the early stage of subsequent infection.

1. Baba, Shuntaro, Tokyo University of Marine Science and Technology, Tokyo, Japan, Presenter
2. Mori, Tatsuya, Tochigi Prefectural Fisheries Experimental Station, Tochigi, Japan, Author
3. Takagi, Yuya, Tochigi Prefectural Fisheries Experimental Station, Tochigi, Japan, Author
4. Wada, Shinpei, Nippon Veterinary and Life Science University, Tokyo, Japan, Author
5. Matsumoto, Megumi, Tokyo University of Marine Science and Technology, Tokyo, Japan, Author
6. Kato, Goshi, Tokyo University of Marine Science and Technology, Tokyo, Japan, Author
7. Sano, Motohiko, Tokyo University of Marine Science and Technology, Tokyo, Japan, Author

Preliminary results on investigation of vertical transmission of Betanodavirus in Sparus aurata

Introduction

Viral nervous necrosis (VNN) is an endemic disease in the Mediterranean, characterized by both horizontal and vertical transmission routes. While vertical transmission has been experimentally confirmed in only a limited number of species – such as European sea bass (Dicentrarchus labrax), grouper (Epinephelus spp.) and Asian sea bass (Lates calcarifer) – it remains a suspected but unproven route in many others. In gilthead sea bream (Sparus aurata), where VNN has only recently been described, data on transmission dynamics are still lacking.

Methodology

Reproductive-aged gilthead sea bream (infected with RG/SJNNV by bath at larval stage) that were asymptomatic carriers of VNN and previously housed at the experimental aquarium of the Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe) were induced to spawn. Egg samples, seminal fluids and the resulting larvae were analyzed for the presence of betanodavirus using RT-qPCR, virological, histological and immunohistochemical analyses. The remaining larvae were kept in controlled conditions and monitored over time for the onset of any clinical signs and mortality associated with VNN.

Result

All samples were tested for betanodavirus by RT-qPCR, and the results demonstrate a sustained positivity in the subjects over time, with inter-organ variability in the distribution patterns. Positivity was found both in eggs and sperms from broodstock (not in all samples). Preliminary results on the first batch of hatched larvae showed negative results in all samples tested by RT-qPCR until 28 dph. Other analyses are still ongoing on the other hatchings.

Conclusions

The aim of this study was to prove the vertical transmission of VNN in gilthead sea bream (Sparus aurata). Preliminary results highlighted that asymptomatic broodstock remain positive several years (up to 7) post infection and that can spread the virus through reproductive fluids.

The development of sufficiently sensitive diagnostic tests for the detection of betanodavirus in asymptomatic carriers is crucial for the implementation of biosecurity plans in marine hatcheries based on the screening of restocking breeders.

Funded by the Italian Ministry of Health project RC IZSVE 09/15 and RC IZSVE 13/22

1. PASCOLI, FRANCESCO, IZSVE, Presenter
2. BERTO, PAOLA, IZSVE, Author
3. BIASINI, LORENA, IZSVE, Author
4. BURATIN, ALESSANDRA, IZSVE, Author
5. MARSELLA, ANDREA, IZSVE, Author
6. TOFFAN, ANNA, IZSVE, Author

Massive groupers die off due to Viral Nervous Necrosis and heatwave in Greece and Italy during 2024

Introduction

Recurrent groupers mortalities have been reported in several areas of the Mediterranean Sea during the last decades. Laboratory investigation revealed that Betanodavirus is the most important pathogen at the base of these events, confirming groupers as highly susceptible species to viral nervous necrosis (VNN). Aim of the study is to present data from 2024 massive fish die off involving large part of Western and Central Mediterranean Sea.

Methodology

Hundreds of fish, mainly belonging to Epinephelus genus, stranded on the coasts of South Greece (with most mortalities recorded in Crete) and South Italy between August and November 2024. Fish collected from different geographic areas were subjected to necropsy to identify the cause of mortality. Bacteriological and parasitological were performed according to standard techniques. Brain and eye were collected and frozen or fixed in RNAlater solution for detection of NNV. In addition, portion of main internal organs were fixed in 10% neutral buffered formalin for histological and immunohistochemical analysis.

Results

Most of the fish showed a low nutritional status. Common lesions included external erosions, ocular lesions and hyper inflated swim bladder. In most cases, Betanodavirus infection was the sole finding; however, occasional additional observations included Vibrio harveyi infection, nodular lesions in the internal organs attributed to putative Ichthyophonus hofferi infection and gill cysts caused by the didymozoid trematod Didymodiclinus sp. All sampled brains tested positive for NNV by qRT-PCR and the viral presence was confirmed by virus isolation in most of them. Sequencing and phylogenetic analyses indicated that all the strains belonged to the RGNNV genotype. The obtained sequences clustered in separated groups corresponding primarily to the geographic origins of fish. Immunohistochemistry performed on selected samples confirmed the presence of immunoprecipitates in nervous tissues.

Conclusions

VNN is endemic in the area investigated in the present study although anomalous mortalities are not reported every year. The extremely high water temperature recorded in 2024 have created the condition for the recrudescence of the diseases in endemic areas. Global warming particularly promote Betanodavirus replication and the subsequent disease outbreaks. Environmental conditions and increased viral load are probably at the base of new species being affected, broadening the range of known susceptible species. Current trends pose a significant threat to important and, in some cases, endangered fish species.

1. TOFFAN, ANNA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DELLE VENEZIE, Presenter
2. ABBADI, MIRIAM, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DELLE VENEZIE, Author
3. PRETTO, TOBIA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DELLE VENEZIE, Author
4. MARSELLA, ANDREA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DELLE VENEZIE, Author
5. BIASINI, LORENA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DELLE VENEZIE, Author
6. TERLIZZI, ANTONIO, DEPT. OF LIFE SCIENCES (DSV),UNIVERSITY OF TRIESTE, ITALY, Author
7. DI NOCERA, FABIO, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL MEZZOGIORNO, PORTICI (NA). ITALY, Author
8. IARIA, CARMELO, INSTITUTE FOR COMPARATIVE, EXPERIMENTAL, FORENSIC AND AQUATIC PATHOLOGY (ICEFAP) “SLAVKO BAMBIR”, UNIVERSITY OF MESSINA, ITALY, Author
9. PERISTERAKI, NOTA, INSTITUTE OF MARINE BIOLOGICAL RESOURCES AND INLAND WATER, GREECE, Author
10. PETIHAKIS, GEORGE, INSTITUTE OF OCEANOGRAPHY, GREECE, Author
11. STAMATAKI, NATALIA, INSTITUTE OF OCEANOGRAPHY, GREECE, Author
12. KATHARIOS, PANTELIS, INSTITUTE OF MARINE BIOLOGY, BIOTECHNOLOGY AND AQUACULTURE, HELLENIC CENTRE FOR MARINE RESEARCH, HERAKLION, GREECE, Author

Harnessing biological novelty to develop therapeutics for the control of proliferative kidney disease in farmed salmonids

Proliferative kidney disease (PKD), caused by the myxozoan, Tetracapsuloides bryosalmonae, is a serious parasitic disease impacting salmonid fish in Europe and USA. Despite the absence of therapeutic control, farmers mitigate against serious losses via pre-exposure, exploiting natural immunity fish develop following recovery from a first exposure and clinical disease. However, such approaches cause production bottlenecks and so vaccine development remains a priority. Our previous studies have shown the fish specific secretory orphan antigen, P14G8 to be partially protective as a DNA vaccine, to act as a putative virulence factor, and to be a highly specific target of antibody responses in exposed and re-exposed fish. Here, our aim is to identify additional fish specific secretory orphan antigens to develop scaffold-displayed multi-epitope therapeutic tools that will be applicable to diverse parasite populations and PKD control.

Published parasite transcriptome data from infected trout and bryozoans were re-aligned to a draft T. bryosalmonae genome and annotated via Trinotate. Full length open reading frames above a cutoff of 1e-5 were defined as unknown. These were subjected to additional bioinformatic analysis, including prediction of; classical secretion, subcellular localisation, secondary structure, glycosylation profile, order / disorder, tyrosine sulphation, alternative splicing, and B cell epitopes via the EpitoPrediktTM. Bioinformatic outputs and host-specific read counts were used as criteria for further selection.

Out of forty-four candidates, sixteen were shortlisted based on fish abundance and confirmed to be fish specific by RT-qPCR. Ten were selected for recombinant epitope-scaffold production. Sixteen protein scaffolds were screened using sera from parasite exposed and unexposed fish and Scaffold-5 identified as having the lowest background via ELISA. Using Epitogen® Technology, eleven recombinant epitope-scaffold proteins (two for P14G8) have been generated in E. coli. The immunogenicity of each epitope scaffold is currently being assessed by ELISA and benchmarked against full length recombinant P14G8 using 100 sera from parasite re-exposed (immune) fish and fish with clinical PKD. Sequence diversity of the most immunogenic epitopes will be assessed using infected kidney tissues representing European and US parasite populations. This will enable further epitope refinement and development of a multi-epitope recombinant scaffold for vaccine testing.

Overall, this work has the potential to create a broad spectrum multi-valent vaccine for PKD, whilst also serving as an enhanced non-invasive diagnostic for parasite exposure or re-exposure.

This work was funded by the European Union’s Horizon Europe research and innovation program under Grant Agreement No. 101084204 (Cure4Aqua).

1. Malintha, GHT, University of Aberdeen. UK, Author
2. Wang, TH, EpitogenX, Author
3. Alnabulsi, A, EpitogenX, Author
4. Wolf, LK, University of Nottingham, Author
5. Bhattacharya, D, University of Veterinary Medicine. Vienna, Author
6. Chan, JTH, University of Veterinary Medicine. Vienna, Author
7. Holzer, AS, University of Veterinary Medicine. Vienna, Author
8. Holland, JW, University of Aberdeen. UK, Presenter

Teaching Aquatic Animal Medicine in a virtual partnership

Introduction

Trainings offered by Veterinary Medicine universities around the world are mainly focused on traditional companion pets and agriculture species, often with little emphasis on exotic animals. There is an increasing demand for professional services in industrial aquaculture, seafood inspection, wildlife management, biomedical research, and for ornamental aquatic pets’ care. A full immersion elective Clerkship on Aquatic Animal Medicine (PDI-636) is offered for 3 weeks to Michigan State University (MSU) veterinary students and selected guests, enriched by a week in virtual partnership with undergraduate veterinary students from the University of Pretoria (UP).

Methodology

PDI-636 is an unconventional veterinary rotation, a full immersion course with lectures followed by interactive assignments, laboratory activities, and field excursions. Due to the time zone difference (6 h) MSU students get morning lectures and learning activities in the afternoon, while UP students get alternative activities in the morning and attend virtual lectures from MSU in the afternoon. Course participants familiarize with a variety of aquatic environments and issues, getting updated knowledge on stressors and heterogenous infectious pathogens causing disease with global relevance for wildlife, pets, fisheries, and aquaculture. Lectures are given by course coordinators and many local and international guest lectures. Adaptive learning approaches involve students in individual, pair, or group activities, designed to foster creative learning while focusing on assigned aquatic health topics. Students can practice scientific info acquisition, with assignments about summarizing scientific articles in presentations, preparing abstracts from WAVMA WebCEPD webinars, and writing diagnostic reports. MSU and UP students virtually work together on real case studies, illustrating their approaches in presentations. Laboratory activities train students in comparative fish anatomy, anesthesia, and euthanasia, followed by biopsy and necropsy procedures, completed by microscopy evaluation of specimens. Technical study visits bring MSU students to public aquaria, research lab, fish hatchery, and a local large aquatic pet shop.

Results

Didactic materials, including guidelines and evaluation rubrics for specific activities, are provided to MSU students through the virtual platform D2L. Each MSU student may discuss midterm evaluation feedback with the course instructor, before getting graded based on clerkship attendance (10%) and assignments (90%). UP students get instead a certificate of participation.

Conclusions

This international training partnership is highly appreciated, providing students and course collaborators from both universities with additional learning opportunities and exposure. Within a One Health perspective, specializing in aquatic animal health may orientate young veterinarians towards new professional career opportunities that become globally available.

1. GORGOGLIONE, BARTOLOMEO, MICHIGAN STATE UNIVERSITY, Presenter
2. Taylor, Gillian, World Aquatic Veterinary Medical Association and University of Pretoria, Author

The influence of environmental conditions on wound healing in Atlantic salmon

Introduction

Despite being one of the leading causes of reduced welfare and mortality in farmed Atlantic salmon, winter ulcer disease remains poorly understood. Rather than being caused by a single pathogen, winter ulcers are the result of opportunistic bacterial infections when hosts have limited ability to fend off infection. Focusing preventive efforts on pathogens can therefor only have limited impact. Instead, a comprehensive approach to health which also considers the impact of environmental conditions on host susceptibility is required.

Methodology

Two experiments were performed to examine the influence of environmental conditions on wound healing. The first experiment tested the impacts of exposure to high, moderate and low levels of individual environmental parameters (oxygen, salinity, swimming speed, daylength), while the second experiment tested the impact of varying multiple environmental parameters in combination. Treatment conditions were chosen to approximate the extremities of real-world conditions that regularly occur in commercial salmon cages.

For both experiments a 4mm skin biopsy punch was used to create uniform injuries in salmon smolt. Injured smolt were then held in pre-defined conditions for 28 days, and sampled at 3, 7, 14 and 28 days post-injury. Photographs of each wound were taken for morphometric analysis, and skin samples collected for histological analysis.

Results

Oxygen, salinity, daylength and swimming speed all significantly influenced the trajectory and progress of wound healing, both singly and in combination. Three days after injury, wounds were the largest in the 24 hour light, low oxygen, and fast swimming speed groups. At the same time, compared to fish held in the control conditions (95% oxygen, 34 ppt salinity, 12:12 LD, 1.6 s tailbeat^-1), wounds were only significantly smaller in the 22 ppt group.  By the end of the first experiment, 28 days post-injury, wounds were the smallest in the 95% oxygen, 22 ppt, 0L and slow swim speed (1.6 s TB^-1) groups, while they were largest in the 60% oxygen, 34 ppt, 24L and fast (1.3 s TB^-1). Combining multiple of the best and worst environmental parameters enhanced and impaired healing, respectively, compared to altering only single parameters.

Conclusions

Effective management of winter ulcer disease in salmon requires a holistic approach. By optimizing environmental conditions to support healing after stressful events such as delousing or encounters with harmful plankton the window for opportunistic infections can be minimized.  Future strategies for safeguarding salmon health should integrate environmental optimization with targeted pathogen control to foster resilience.

1. OLDHAM, TINA, INSTITUTE OF MARINE RESEARCH NORWAY, Presenter