Redefining piscine lactococcosis.

Piscine lactococcosis is a significant threat to cultured and wild fish populations worldwide. The disease typically presents as a per-acute to acute hemorrhagic septicemia causing high morbidity and mortality, recalcitrant to antimicrobial treatment or management interventions. Historically, the disease was attributed to the gram-positive pathogen Lactococcus garvieae. However, recent work has revealed three distinct lactococcosis-causing bacteria (LCB)-L. garvieae, L. petauri, and L. formosensis-which are phenotypically and genetically similar, leading to widespread misidentification. An update on our understanding of lactococcosis and improved methods for identification are urgently needed. To this end, we used representative isolates from each of the three LCB species to compare currently available and recently developed molecular and phenotypic typing assays, including whole-genome sequencing (WGS), end-point and quantitative PCR (qPCR) assays, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), API 20 Strep and Biolog systems, fatty acid methyl ester analysis (FAME), and Sensititre antimicrobial profiling. Apart from WGS, sequencing of the gyrB gene was the only method capable of consistent and accurate identification to the species and strain level. A qPCR assay based on a putative glycosyltransferase gene was also able to distinguish L. petauri from L. garvieae/formosensis. Biochemical tests and MALDI-TOF MS showed some species-specific patterns in sugar and fatty acid metabolism or protein profiles but should be complemented by additional analyses. The LCB demonstrated overlap in host and geographic range, but there were relevant differences in host specificity, regional prevalence, and antimicrobial susceptibility impacting disease treatment and prevention. IMPORTANCE: Lactococcosis affects a broad range of host species, including fish from cold, temperate, and warm freshwater or marine environments, as well as several terrestrial animals, including humans. As such, lactococcosis is a disease of concern for animal and ecosystem health. The disease is endemic in European and Asian aquaculture but is rapidly encroaching on ecologically and economically important fish populations across the Americas. Piscine lactococcosis is difficult to manage, with issues of vaccine escape, ineffective antimicrobial treatment, and the development of carrier fish or biofilms leading to recurrent outbreaks. Our understanding of the disease is also widely outdated. The accepted etiologic agent of lactococcosis is Lactococcus garvieae. However, historical misidentification has masked contributions from two additional species, L. petauri and L. formosensis, which are indistinguishable from L. garvieae by common diagnostic methods. This work is the first comprehensive characterization of all three agents and provides direct recommendations for species-specific diagnosis and management.

Evaluation of three inactive vaccines against Veronaea botryosa infection in white sturgeon (Acipenser transmontanus).

Veronaea botryosa is the etiological agent of a systemic phaeohyphomycosis known as "fluid belly" in white sturgeon (Acipenser transmontanus). Fluid belly is a critical disease affecting sturgeon aquaculture and the caviar industry for which there are no commercially available vaccines or approved antifungal treatments to manage outbreaks. The primary aim of this study was to investigate the effect of a V. botryosa [conidia], a V. botryosa [mold], and a Saccharomyces cerevisiae [yeast] formalin-killed vaccine on sturgeon immune responses to fungal challenge. Immunization consisted of an initial intracoelomic injection with one of the three treatment preparations, followed by a vaccine booster four weeks later by the same route and dose. Experimental challenge by intramuscular injection with a virulent V. botryosa conidia suspension followed after another four weeks. Non-challenged control fish received injections of PBS. The inactivated vaccines proved safe for white sturgeon fingerlings. Sturgeon immunized with either V. botryosa [mold] or S. cerevisiae [yeast] exhibited a significantly different pro-inflammatory response upon challenge with V. botryosa compared to non-immunized fish. Challenged fish developed clinical signs similar to those reported during natural outbreaks of fluid belly. Positive control treatments (those not immunized but challenged with V. botryosa) experienced the highest mortality; however, survival curves were similar amongst all treatments (p < 0.05). Furthermore, the S. cerevisiae [yeast] vaccine resulted in comparatively lower fungal persistence and fewer lesions following histological analysis. Further efforts evaluating the potential of Saccharomyces spp. as a vaccine candidate against fluid belly are warranted.

Francisella sciaenopsi sp. nov. isolated from diseased red drum Sciaenops ocellatus in Florida, USA.

Piscine francisellosis is one of the most important bacterial diseases affecting various fish species worldwide. Francisella orientalis, F. noatunensis, and F. salimarina (F. marina) have been reported as etiological agents of disease in fish. A Francisella sp. was isolated from several diseased red drum Sciaenops ocellatus experiencing morbidity in Florida, USA, in 2008. In this study, molecular and phenotypic characterization of the recovered isolate was conducted. Phenotypically, the isolate showed a biochemical reaction profile distinct from that of F. orientalis and F. salimarina. Although the 16S rRNA sequence of this isolate shared 99.61% identity to the type strain of F. philomiragia O#319LT, whole genome analysis (average nucleotide identity <95%; digital DNA-DNA hybridization <70%) and a multilocus sequence analysis of 8 concatenated housekeeping genes in comparison with other Francisella spp. indicated that this isolate was a novel Francisella species, more closely related to F. orientalis. Immersion, intracoelomic injection, and co-habitation challenges using a Nile tilapia Oreochromis niloticus fingerling model of infection were done to investigate virulence in a piscine model. Variably pigmented granulomas and pigmented macrophage aggregates were observed in the kidneys and spleens of the challenged fish, but no mortality was recorded during the 15 d challenge period, suggesting that this novel Francisella sp. might be an opportunistic pathogen of fish. Based on the phenotypic and genotypic differences from other Francisella spp. observed in this study, we propose the name Francisella sciaenopsi sp. nov. for this novel isolate.

Erysipelas with preferential brain and skin involvement in a Mediterranean bottlenose dolphin Tursiops truncatus.

Infections by Erysipelothrix rhusiopathiae occur in domestic animals and cause the disease known as 'erysipelas'. The ubiquity of Erysipelothrix spp. makes infection possible in a wide range of vertebrates and invertebrates. Cetaceans are highly susceptible to erysipelas, especially those under human care. The number of cases documented in wild cetaceans is low, the pathogenesis is incompletely understood, and the full spectrum of lesions is not well defined. The possible serotypes and species of the genus that can cause disease are unknown. In October 2022, a common bottlenose dolphin Tursiops truncatus stranded in Vilassar de Mar (Catalonia) showing skin lesions consistent with 'diamond skin disease', a characteristic lesion of erysipelas shared by swine and cetaceans. Necropsy was performed following standardized procedures, and multiple samples were taken for histopathology and bacteriology. Erysipelothrix sp. grew in pure culture in many tissue samples. Genetic characterization by multi-locus sequence analysis identified the species as E. rhusiopathiae. Histologically, the main lesions were an intense suppurative vasculitis of leptomeningeal arteries and veins with abundant intramural Gram-positive bacilli and meningeal hemorrhages. Meningeal lesions were considered the cause of death. The affected skin showed moderate suppurative dermatitis. Herein we document a case of erysipelas in a Mediterranean common bottlenose dolphin with unusual lesions in the leptomeningeal vessels and marked skin tropism. To our knowledge, this is the first case of severe brain involvement in erysipelas in a cetacean. We also provide a review of available cases in wild cetaceans, to highlight the characteristics of the disease and improve future diagnosis.

Temperature-dependent alterations in the proteome of the emergent fish pathogen Edwardsiella piscicida.

Edwardsiella piscicida is an emerging bacterial pathogen and the aetiological agent of edwardsiellosis among cultured and wild fish species globally. The increased frequency of outbreaks of this Gram-negative, facultative intracellular pathogen pose not only a threat to the aquaculture industry but also a possible foodborne/waterborne public health risk due to the ill-defined zoonotic potential. Thus, understanding the role of temperature on the virulence of this emerging pathogen is essential for comprehending the pathogenesis of piscine edwardsiellosis in the context of current warming trends associated with climate change, as well as providing insight into its zoonotic potential. In this study, significant temperature-dependent alterations in bacterial growth patterns were observed, with bacterial isolates grown at 17°C displaying higher peak growth sizes, extended lag times, and slower maximal growth rates than isolates grown at 27or 37°C. When E. piscicida isolates were grown at 37°C compared to 27 and 17°C, mass spectrometry analysis of the E. piscicida proteome revealed significant downregulation of crucial virulence proteins, such as Type VI secretion system proteins and flagellar proteins. Although in vivo models of infection are warranted, this in vitro data suggests possible temperature-associated alterations in the virulence and pathogenic potential of E. piscicida in poikilotherms and homeotherms.

Temperature-associated virulence, species susceptibility and interspecies transmission of a Lactococcus petauri strain from rainbow trout.

Lactococcus petauri is an important emergent aquaculture pathogen in the USA. To better understand environmental conditions conducive to piscine lactococcosis and the susceptibility of fish species, laboratory-controlled challenges were used as models of infection. Rainbow trout Oncorhynchus mykiss maintained at 13 or 18°C were challenged by intracoelomic (ICe) injection with 101, 103 or 105 colony-forming units per fish (CFU fish-1) and monitored for 21 d. At 13°C, trout experienced mortalities of 7, 7 and 0%, and bacterial persistence of 0, 20 and 0% in survivors, respectively. When exposed to the same bacterial doses, trout maintained at 18°C experienced mortalities of 59, 84 and 91%, and bacterial persistence of 60, 66 and 0% in survivors, confirming a significant role of temperature in the pathogenesis of lactococcosis. Additionally, the susceptibility of rainbow trout, Chinook salmon Oncorhynchus tshawytscha, white sturgeon Acipenser transmontanus, Nile tilapia Oreochromis niloticus, and koi Cyprinus carpio to infection by L. petauri was compared using ICe challenges at 18°C. Trout and salmon experienced 96 and 56% cumulative mortality, respectively, and 17% of surviving salmon remained persistently infected. There were no mortalities in the other fish species, and no culturable bacteria recovered at the end of the challenge. However, when surviving fish were used in further cohabitation trials, naïve trout housed with previously exposed tilapia exhibited 6% mortality, demonstrating that non-salmonids can become sub-clinical carriers of this pathogen. The data obtained provide useful information regarding temperature-associated virulence, fish species susceptibility, and potential carrier transmission of L. petauri that can be used in the development of better management practices to protect against piscine lactococcosis.

Detection and virulence of Lactococcus garvieae and L. petauri from four lakes in southern California.

OBJECTIVE: The first objective of the study aimed to detect the presence of Lactococcus petauri, L. garvieae, and L. formosensis in fish (n = 359) and environmental (n = 161) samples from four lakes near an affected fish farm in California during an outbreak in 2020. The second objective was to compare the virulence of the Lactococcus spp. in Rainbow Trout Oncorhynchus mykiss and Largemouth Bass Micropterus salmoides. METHODS: Standard bacterial culture methods were used to isolate Lactococcus spp. from brain and posterior kidney of sampled fish from the four lakes. Quantitative PCR (qPCR) was utilized to detect Lactococcus spp. DNA in fish tissues and environmental samples from the four lakes. Laboratory controlled challenges were conducted by injecting fish intracoelomically with representative isolates of L. petauri (n = 17), L. garvieae (n = 2), or L. formosensis (n = 4), and monitored for 14 days postchallenge (dpc). RESULT: Lactococcus garvieae was isolated from the brains of two Largemouth Bass in one of the lakes. Lactococcus spp. were detected in 14 fish (8 Bluegills Lepomis macrochirus and 6 Largemouth Bass) from 3 out of the 4 lakes using a qPCR assay. Of the collected environmental samples, all 4 lakes tested positive for Lactococcus spp. in the soil samples, while 2 of the 4 lakes tested positive in the water samples through qPCR. Challenged Largemouth Bass did not show any signs of infection postinjection throughout the challenge period. Rainbow Trout infected with L. petauri showed clinical signs within 3 dpc and presented a significantly higher cumulative mortality (62.4%; p < 0.0001) at 14 dpc when compared to L. garvieae (0%) and L. formosensis (7.5%) treatments. CONCLUSION: The study suggests that qPCR can be used for environmental DNA monitoring of Lactococcus spp. and demonstrates virulence diversity between the etiological agents of piscine lactococcosis.

Development of a quantitative polymerase chain reaction assay for detection of the aetiological agents of piscine lactococcosis.

Piscine lactococcosis is an emergent bacterial disease that is associated with high economic losses in many farmed and wild aquatic species worldwide. Early and accurate detection of the causative agent of piscine lactococcosis is essential for management of the disease in fish farms. In this study, a TaqMan quantitative polymerase chain reaction (qPCR) targeting the 16S-23S rRNA internal transcribed spacer region was developed and validated. Validation of the qPCR was performed with DNA of previously typed L. petauri and L. garvieae recovered from different aquatic hosts from distinct geographical locations, closely related bacterial species and common pathogens in trout aquaculture. Further diagnostic sensitivity and specificity was investigated by screening of fish, water and faecal samples. The developed qPCR assay showed high specificity, sensitivity and accuracy in detection of L. petauri and L. garvieae with lack of signals from non-target pathogens, and in screening of rainbow trout (Oncorhynchus mykiss) posterior kidney and environmental samples. The detection limit of the qPCR was four amplicon copies. Moreover, the sensitivity of the qPCR assay was not affected by presence of non-target DNA from either fish or environmental samples. The robustness, specificity and sensitivity of the developed qPCR will facilitate fast and accurate diagnosis of piscine lactococcosis to establish appropriate control measures in fish farms and aquaria.

Metal Complexes of a 5-Nitro-8-Hydroxyquinoline-Proline Hybrid with Enhanced Water Solubility Targeting Multidrug Resistant Cancer Cells.

Multidrug resistance (MDR) in cancer is one of the major obstacles of chemotherapy. We have recently identified a series of 8-hydroxyquinoline Mannich base derivatives with MDR-selective toxicity, however with limited solubility. In this work, a novel 5-nitro-8-hydroxyquinoline-proline hybrid and its Rh(η5-C5Me5) and Ru(η6-p-cymene) complexes with excellent aqueous solubility were developed, characterized, and tested against sensitive and MDR cells. Complex formation of the ligand with essential metal ions was also investigated using UV-visible, circular dichroism, 1H NMR (Zn(II)), and electron paramagnetic resonance (Cu(II)) spectroscopic methods. Formation of mono and bis complexes was found in all cases with versatile coordination modes, while tris complexes were also formed with Fe(II) and Fe(III) ions, revealing the metal binding affinity of the ligand at pH 7.4: Cu(II) > Zn(II) > Fe(II) > Fe(III). The ligand and its Rh(III) complex displayed enhanced cytotoxicity against the resistant MES-SA/Dx5 and Colo320 human cancer cell lines compared to their chemosensitive counterparts. Both organometallic complexes possess high stability in solution, however the Ru(II) complex has lower chloride ion affinity and slower ligand exchange processes, along with the readiness to lose the arene ring that is likely connected to its inactivity.

Quantitative PCR for detection and quantification of Veronaea botryosa in fish and environmental samples.

Systemic phaeohyphomycosis, aka 'fluid belly', is one of the most important emergent diseases in sturgeon Acipenser spp. aquaculture. The etiologic agent is the saprobic, dematiaceous fungus Veronaea botryosa. Effective vaccines and chemotherapeutic treatments are currently unavailable. Additionally, the fungus is a slow-growing organism, taking from 10-15 d for colonies to be observed in agar media. To this end, a specific quantitative PCR (qPCR) targeting the V. botryosa ß-tubulin gene was developed and validated. The specificity of the assay to V. botryosa was initially confirmed in silico and in vivo against common fungal fish pathogens, including closely related members of the order Chaetothyriales (Exophiala spp.) and other black pigmented fungi (Alternaria spp. and Cladosporium spp.), as well as tissues from uninfected sturgeon. The assay possessed high clinical specificity (100%) and clinical sensitivity (74%) in detecting V. botryosa DNA in splenic tissues from laboratory-infected sturgeon. Using V. botryosa genomic DNA as a template, the limit of detection was equivalent to 10 conidia, and the method was found suitable for the detection of fungal DNA in fresh and formalin-fixed tissues. In addition, the presence of non-target DNA from white sturgeon did not influence assay sensitivity. The developed qPCR assay is a sensitive, specific, and rapid diagnostic method for the detection and quantification of V. botryosa DNA from white sturgeon tissues.

Pathogenesis of Erysipelothrix piscisicarius infection in tiger barbs (Puntigrus tetrazona).

Erysipelothrix piscisicarius is an emerging bacterial pathogen and the aetiologic agent of piscine erysipelosis, a recently recognized disease of ornamental fish. However, little is known regarding the dynamics of infection in fish. The purpose of this study was to gain a better understanding of the pathogenesis of piscine erysipelosis in the tiger barb (Puntigrus tetrazona) by investigating tissue tropisms and responses to bacterial dissemination following immersion challenge with a virulent strain recovered from diseased fish. The challenge resulted in 83% mortality by day 16. Erysipelothrix piscisicarius DNA was first detected in the skin using quantitative PCR, and bacteria were visualized in association with microscopic lesions on day 4. By day 8, E. piscisicarius DNA was further detected in intestines, hearts, spleens, gills and skin; parenchymal organs were largely spared. The data suggest a primary cutaneous portal of entry and tropism for collagenous tissues, particularly those within vascular walls. Initial spread occurs directly from the dermis into interstitial areas of skeletal muscle, then centrally to the peritoneum and coelomic cavity following collagenous tissue pathways. Although histopathology revealed widespread bacterial dissemination over time, the severity of skin and muscle lesions with high levels of bacterial DNA identifies these tissues as primary targets of infection.

USE OF TOPICAL TREATMENTS AND EFFECTS OF WATER TEMPERATURE ON WOUND HEALING IN COMMON CARP (CYPRINUS CARPIO).

Skin lesions are frequently diagnosed in fish medicine. Although systemic fish treatments exist, little is known about the efficacy of topical drugs on fish skin lesions. This study aimed to investigate the efficacy of medical-grade honey and silver sulfadiazine on skin lesions using common carp (Cyprinus carpio) as a model. Additionally, the effect of temperature on the wound healing process was evaluated. Punch biopsies were generated on six fish per treatment group under anesthesia. Treatment groups received one of the following topical medications after wounding: Dr. Nordyke's Wound Honey, MicroLyte Ag Vet, or SilvaSorb Gel. Nontreated positive control groups were similarly wounded but did not receive topical treatment. Fish were housed at 10°C to 13°C or 18°C to 21°C for 29 days. Macroscopic evaluation and image collection of wounds were performed on days 0, 4, 8, 12, 21, and 29 after wounding to compare changes in wound areas and inflammation over time. On day 29, tissue samples were collected for histologic analysis. From day 12 after wounding onward, wounds in positive controls maintained at 18°C to 21°C were significantly smaller (days 12, 21, and 29: P < 0.0001) compared with positive controls kept at 10°C to 13°C. There was an overall improvement in macroscopic appearance in honey-treated groups compared with positive controls on day 12 after wounding at 18°C to 21°C (P = 0.001), whereas with the use of Microlyte and Silvasorb, wounds had increased inflammation grades (P < 0.0001 and P < 0.0001, respectively) with enlarged wound areas (P < 0.0001 and P < 0.001, respectively) in comparison with positive controls on day 12 after wounding at 18°C to 21°C. This study suggests that topical use of medical-grade honey produces positive effects on wound healing in the carp model and higher water temperatures enhance the effects, whereas the use of silver sulfadiazine and lower water temperatures delays or worsens the wound healing process.

LIQUID NITROGEN CRYOSURGERY FOR CUTANEOUS AND OCULAR NEOPLASMS IN KOI (CYPRINUS CARPIO) AND GOLDFISH (CARASSIUS AURATUS): EIGHT CASES (2018-2019).

Cryosurgery, also known as cryotherapy and cryoablation, is a promising surgical technique that employs highly localized freezing to destroy damaged and diseased tissue, including benign and malignant neoplasms. This procedure has been reported in the treatment of chromatophoromas, fibromas, and peripheral nerve sheath tumors in piscine patients. This study presents eight clinical cases of cryosurgery on cyprinid pet fish for a wide array of neoplastic masses, including chromatophoromas, squamous cell carcinoma, and sarcomas that were diagnosed by histopathology. Surgical excision of external masses, liquid nitrogen cryotherapy, injectable medications (meloxicam and danofloxacin), and topical medical-grade honey were applied to the patients after biopsy sampling. Five out of seven cutaneous cases and two out of three ocular cases had complete resolution without recurrence for at least three months posttreatment. Treatment was unsuccessful for two of the cutaneous cases in which the cutaneous masses were extremely invasive, resulting in severe ulceration and deep invasion into the coelomic cavity. One of the ocular cases involved a corneal mass that did not change in size and had no complications after treatments, suggesting that the treatment might be useful in limiting growth. The effectiveness of cryotherapy appears to correlate with the tumor type, as well as the stage and progression of tumor invasion.

Non-lethal diagnostic methods for koi herpesvirus in koi Cyprinus carpio.

Cyprinid herpesvirus 3, also known as koi herpesvirus (KHV), is a viral pathogen responsible for mass mortalities of carp worldwide. In this study, we compared the sensitivity and specificity of ELISA and quantitative PCR (qPCR) methods for the diagnosis of KHV in experimentally infected koi Cyprinus carpio over an 11 mo period. Koi were exposed to KHV at 18 ± 1°C (permissive temperatures for KHV disease) in laboratory-controlled conditions. At 21 d post challenge, the temperature in the system was decreased to <15°C (non-permissive temperature for KHV disease), and fish were monitored for the following 11 mo. At different time points throughout the study, samples of blood and gills were collected from exposed and control koi and subjected to qPCR and ELISA. Survival proportions of 53.3 and 98.8% in exposed and control treatments, respectively, were recorded at the end of the challenge. Traditional receiver-operating characteristic analysis was used to compare the sensitivity of the ELISA and blood and gill qPCR during permissive and non-permissive temperatures. ELISA was superior to qPCR of gills and whole-blood samples in detecting previous exposure to KHV. Similar results were obtained in a second experiment exposing koi to KHV and inducing persistent infection at >30°C (non-permissive temperature for KHV disease). Finally, KHV ELISA specificity was confirmed using cyprinid herpesvirus 1-exposed koi through a period of 3 mo. This study demonstrates that the combination of ELISA and gill qPCR should be recommended in the diagnosis of KHV exposure of suspected carrier-state fish.

Sulforaphane as an adjunctive treatment for irritability in children with autism spectrum disorder: A randomized, double-blind, placebo-controlled clinical trial.

AIM: Irritability related to autism spectrum disorder (ASD) complicates the management of ASD patients at home and in clinical settings. In this randomized, double-blind, placebo-controlled clinical trial, we aimed to investigate the beneficial effects of adjuvant treatment with risperidone and sulforaphane in alleviating the irritability of children with ASD. METHODS: Sixty drug-free patients aged 4-12 years were randomly assigned to one of two groups receiving risperidone plus sulforaphane or placebo. Risperidone was started with a daily dose of 0.25 mg in patients weighing <20 kg and 0.5 mg in those weighing ≥20 kg and increased stepwise to reach a maximum of 1 mg (<20 kg), 2.5 mg (20-45 kg), and 3.5 mg (>45 kg). Sulforaphane was administered at a daily dose of 50 µmol (≤45 kg) or 100 µmol (>45 kg). The participants were assessed with the Aberrant Behavior Checklist - Community Edition at baseline and at Weeks 5 and 10. RESULTS: Compared to the placebo group, ASD patients in the sulforaphane group showed greater improvements in Irritability score (primary outcome measure; P = 0.001) and Hyperactivity/Noncompliance score (secondary outcome measure; P = 0.015), and significant Time × Treatment effect for Irritability (P = 0.007) and Hyperactivity/Noncompliance (P = 0.008). However, no difference was seen in improvements in the other secondary measures: Lethargy/Social Interaction score, Stereotypic Behavior score, Inappropriate Speech score, and frequency of adverse events. CONCLUSION: Our results support the safety and efficacy of sulforaphane as an adjuvant to risperidone for improvement of irritability and hyperactivity symptoms in children with ASD.

Comparative Evaluation of Booster Vaccine Efficacy by Intracoelomic Injection and Immersion with a Whole-Cell Killed Vaccine against Lactococcus petauri Infection in Rainbow Trout (Oncorhynchus mykiss).

Lactococcus petauri is an important emergent bacterial pathogen of salmonids in the USA. The purpose of this study was to evaluate the protection conferred to rainbow trout (Oncorhynchus mykiss) against L. petauri by formalin-killed vaccines in immersion and injectable forms, as well as the enhanced protection afforded by booster vaccination. In the first challenge, fish were immunized via intracoelomic injection (IC) or immersion (Imm) routes alone. Approximately 418 degree days (Temperature in degree Celsius × days post-immunization) (dd) Imm, or 622 dd IC post-vaccination, fish were challenged via IC with wild-type L. petauri. In the second experiment, initial Imm vaccination was followed by booster vaccination via Imm or IC routes 273 dd post-immunization along with appropriate PBS controls. The various vaccination protocol efficacies were evaluated by challenging fish with L. petauri by cohabitation with diseased fish 399 dd post-booster administration. A relative percent survival (RPS) of 89.5% and 28% was recorded in the IC and Imm single immunization treatments, respectively. In the second study, an RPS of 97.5%, 10.2%, 2.6% and -10.1% plus approximately 0%, 50%, 20%, and 30% bacterial persistence was recorded in the Imm immunized + IC boosted, Imm immunized + mock IC boosted, Imm immunized + Imm boosted, and Imm immunized + mock Imm boosted treatments, respectively. Only the Imm immunized + IC injection boosted treatments provided significant protection when compared to unvaccinated and challenged treatments (p < 0.05). In conclusion, although both Imm and IC vaccines appear safe for trout, the inactivated Imm vaccines seem to provide only mild and temporary protection against lactococcosis; whereas IC immunized trout develop a significantly stronger protective response in both challenges.

Atypical flavobacteria recovered from diseased fish in the Western United States.

Flavobacterial diseases, caused by bacteria in the order Flavobacteriales, are responsible for devastating losses in farmed and wild fish populations worldwide. The genera Flavobacterium (Family Flavobacteriaceae) and Chryseobacterium (Weeksellaceae) encompass the most well-known agents of fish disease in the order, but the full extent of piscine-pathogenic species within these diverse groups is unresolved, and likely underappreciated. To identify emerging agents of flavobacterial disease in US aquaculture, 183 presumptive Flavobacterium and Chryseobacterium isolates were collected from clinically affected fish representing 19 host types, from across six western states. Isolates were characterized by 16S rRNA gene sequencing and phylogenetic analysis using the gyrB gene. Antimicrobial susceptibility profiles were compared between representatives from each major phylogenetic clade. Of the isolates, 52 were identified as Chryseobacterium species and 131 as Flavobacterium. The majority of Chryseobacterium isolates fell into six clades (A-F) consisting of ≥ 5 fish isolates with ≥ 70% bootstrap support, and Flavobacterium into nine (A-I). Phylogenetic clades showed distinct patterns in antimicrobial susceptibility. Two Chryseobacterium clades (F & G), and four Flavobacterium clades (B, G-I) had comparably high minimal inhibitory concentrations (MICs) for 11/18 antimicrobials tested. Multiple clades in both genera exhibited MICs surpassing the established F. psychrophilum breakpoints for oxytetracycline and florfenicol, indicating potential resistance to two of the three antimicrobials approved for use in finfish aquaculture. Further work to investigate the virulence and antigenic diversity of these genetic groups will improve our understanding of flavobacterial disease, with applications for treatment and vaccination strategies.

Efficacy of a multidose acyclovir protocol against cyprinid herpesvirus 3 infection in koi (Cyprinus carpio).

OBJECTIVE: To evaluate the effect of a multidose acyclovir protocol on koi herpesvirus (KHV) viral load and mortality in a cohabitation challenge. ANIMALS: 180 koi fish. PROCEDURES: Forty fish (shedders) were immersed in a 0.5 KHV plaque-forming units/mL static bath for 8 hours. Mock shedders were treated similarly but exposed to cell culture media. KHV shedders were then transferred into 8 tanks (5 shedders per tank) containing 10 naïve fish (cohabitants) each. Fish in the acyclovir group (AT) received a 10 mg/kg acyclovir intracoelomic injection 1, 3, and 6 days after the first confirmed KHV mortality. Positive controls (PC) were treated similarly but received sterile saline injections. Negative controls (NC) were exposed to mock shedders. Morbidity and mortality were evaluated daily for 50 days post-challenge. Quantitative PCR was used to determine viral load in the gill biopsies of shedders and cohabitants collected at days 19 (T1), 22 (T2), 25 (T3), 34 (T4), and 50 (T5) post-challenge. RESULTS: Survival curves analyzed by the Gehan-Breslow-Wilcoxon method revealed a delayed onset of mortalities and a significantly lower KHV load at T2 and T3 detected in AT cohabitant fish (P = .042) compared to PC group. However, there were no significant differences in overall mortality or viral loads at T5. CLINICAL RELEVANCE: The acyclovir protocol used in this study did not control viral infection or mortality at the end of the 50-day trial. Shorter intervals between injections could improve outcomes, but the additional stress inflicted by handling should be considered. Exploring other therapeutic alternatives and doses is warranted.

Expression of immune markers of white sturgeon (Acipenser transmontanus) during Veronaea botryosa infection at different temperatures.

Systemic phaeohyphomycosis caused by Veronaea botryosa is one of the most important emergent diseases to affect sturgeon aquaculture in North America. White sturgeon (Acipenser transmontanus) cultured at temperatures above 15 °C are at higher risk of severe disseminated disease and higher mortalities. Despite this, little is known regarding disease pathogenesis and the immune response to infection. The objective of this study was to investigate the acute (2 days post-challenge [dpc]) and chronic (32 dpc) response of white sturgeon at 13 °C and 18 °C challenged with V. botryosa via intramuscular injection, using gene expression analysis of a diverse array of soluble immune and inflammatory mediators. Significantly greater amounts of irf8 (p < 0.05) and tfg-ß (p < 0.05) genes were detected in gills of exposed fish at 18 °C when compared to those at 13 °C 32 dpc. Transcript levels of haptoglobin, serotransferrin, serum amyloid, cathelicidin, tnf-α, and il-17 were significantly increased in splenic tissues of challenged fish maintained at 18 °C late in infection (p < 0.05). However, only haptoglobin and serotransferrin transcript abundance were significantly greater in exposed fish when compared to controls 32dpc. Moreover, haptoglobin transcripts at this time point were significantly greater in exposed fish at 18 °C when compared to those challenged at 13 °C. Fewer differences were detected in fish kept at 13 °C. In agreement with transcript quantification, western blot assessment of haptoglobin showed increased levels in the challenged fish maintained at 18 °C.

Analysis of the white sturgeon (Acipenser transmontanus) immune response during immunostimulation and Veronaea botryosa infection.

Systemic phaeohyphomycosis caused by Veronaea botryosa is regarded as an important emerging mycotic disease of sturgeon aquaculture. However, no vaccines or treatments are currently available. The effects of dietary ß-glucan supplementation on resistance to V. botryosa infection was examined in controlled challenges by exposing immunostimulated and control fish to ~7.25 × 105 fungal spores/fish via intra-muscular injection. Six weeks post-challenge, cumulative mortality was determined and antibodies to acute phase-proteins (APP) were used to quantify the conserved APP peptides in the serum of challenged and control fish using Western blot. Transcript levels for all tested pro-inflammatory cytokines, APP, and regulatory cytokines in the spleen were similar amongst treatments at the end of the three-week feeding period. However, significantly higher survival occurred in fingerlings fed 0.3% ß-glucans compared to non-immunostimulated fish groups (p < 0.05) six weeks post-challenge. A strong proinflammatory response was detected in exposed treatment groups, and greater survival at 6 weeks was associated with higher transcript abundance of Il-17 in fish fed ß-glucans. Findings support the important role of this cytokine in response to fungal infection.