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Heckman TI, Yazdi Z, Older CE, Griffin MJ, Waldbieser GC, Chow AM, Medina Silva I, Anenson KM, García JC, LaFrentz BR, Slavic D, Toohey-Kurth KL, Yant P, Fritz HM, Henderson EE, McDowall R, Cai H, Adkison M, Soto E. Redefining piscine lactococcosis. Appl Environ Microbiol 2024:e0234923. [PMID: 38597602 DOI: 10.1128/aem.02349-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Accepted: 03/10/2024] [Indexed: 04/11/2024] Open
Abstract
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.
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Affiliation(s)
- Taylor I Heckman
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Zeinab Yazdi
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Caitlin E Older
- USDA-ARS, Warmwater Aquaculture Research Unit, Stoneville, Mississippi, USA
| | - Matt J Griffin
- College of Veterinary Medicine, Mississippi State University, Stoneville, Mississippi, USA
| | | | - Alexander M Chow
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Isabella Medina Silva
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Kelsey M Anenson
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Julio C García
- USDA-ARS, Aquatic Animal Health Research Unit, Auburn, Alabama, USA
| | | | - Durda Slavic
- Animal Health Laboratory, University of Guelph, Ontario, Canada
| | - Kathy L Toohey-Kurth
- California Animal Health and Food Safety Laboratory, University of California, Davis, California, USA
| | - Paula Yant
- California Animal Health and Food Safety Laboratory, University of California, Davis, California, USA
| | - Heather M Fritz
- California Animal Health and Food Safety Laboratory, University of California, Davis, California, USA
| | - Eileen E Henderson
- California Animal Health and Food Safety Laboratory, University of California, Davis, California, USA
| | | | - Hugh Cai
- Animal Health Laboratory, University of Guelph, Ontario, Canada
| | - Mark Adkison
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Esteban Soto
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
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Littman EM, Heckman TI, Yazdi Z, Veek T, Mukkatira K, Adkison M, Powell A, Camus A, Soto E. Temperature-associated virulence, species susceptibility and interspecies transmission of a Lactococcus petauri strain from rainbow trout. Dis Aquat Organ 2023; 155:147-158. [PMID: 37706645 DOI: 10.3354/dao03747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/15/2023]
Abstract
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.
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Affiliation(s)
- Eric Maxwell Littman
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
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Abraham T, Yazdi Z, Littman E, Shahin K, Heckman TI, Quijano Cardé EM, Nguyen DT, Hu R, Adkison M, Veek T, Mukkatira K, Richey C, Kwak K, Mohammed HH, Ortega C, Avendaño-Herrera R, Keleher W, LePage V, Gardner I, Welch TJ, Soto E. Detection and virulence of Lactococcus garvieae and L. petauri from four lakes in southern California. J Aquat Anim Health 2023; 35:187-198. [PMID: 37749801 DOI: 10.1002/aah.10188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 04/24/2023] [Accepted: 04/29/2023] [Indexed: 09/27/2023]
Abstract
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.
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Affiliation(s)
- Taylor Abraham
- School of Veterinary Medicine, University of California-Davis, Davis, California, USA
| | - Zeinab Yazdi
- School of Veterinary Medicine, University of California-Davis, Davis, California, USA
| | - Eric Littman
- School of Veterinary Medicine, University of California-Davis, Davis, California, USA
| | - Khalid Shahin
- School of Veterinary Medicine, University of California-Davis, Davis, California, USA
- Aquatic Animals Diseases Laboratory, National Institute of Oceanography and Fisheries, Suez, Egypt
| | - Taylor I Heckman
- School of Veterinary Medicine, University of California-Davis, Davis, California, USA
| | | | - Diem Thu Nguyen
- School of Veterinary Medicine, University of California-Davis, Davis, California, USA
| | - Ruixue Hu
- School of Veterinary Medicine, University of California-Davis, Davis, California, USA
| | - Mark Adkison
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Tresa Veek
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Kavery Mukkatira
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Christine Richey
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Kevin Kwak
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Haitham H Mohammed
- Department of Rangeland, Wildlife and Fisheries Management, College of Agriculture and Life Sciences, Texas A&M University, College Station, Texas, USA
| | - Cesar Ortega
- Centro de Investigación y Estudios Avanzados en Salud Animal, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma del Estado de México, Toluca, Mexico
| | - Ruben Avendaño-Herrera
- Laboratorio de Patología de Organismos Acuáticos y Biotecnología Acuícola, Facultad de Ciencias de la Vida, Universidad Andrés Bello and Fondo de Financiamiento de Centros de Investigación en Áreas Prioritarias, Centro Interdisciplinario de Investigación en Acuicultura Sustentable, Viña del Mar, Chile
| | | | | | - Ian Gardner
- Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
| | - Timothy J Welch
- U.S. Department of Agriculture, Agricultural Research Service, National Center for Cool and Coldwater Aquaculture, Leetown, West Virginia, USA
| | - Esteban Soto
- School of Veterinary Medicine, University of California-Davis, Davis, California, USA
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de Ruyter T, Littman E, Yazdi Z, Adkison M, Camus A, Yun S, Welch TJ, Keleher WR, Soto E. 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). Pathogens 2023; 12:pathogens12050632. [PMID: 37242302 DOI: 10.3390/pathogens12050632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 04/07/2023] [Accepted: 04/08/2023] [Indexed: 05/28/2023] Open
Abstract
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.
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Affiliation(s)
- Tryssa de Ruyter
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA
- School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Eric Littman
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA
| | - Zeinab Yazdi
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA
| | - Mark Adkison
- California Department of Fish and Wildlife, Rancho Cordova, CA 95670, USA
| | - Alvin Camus
- Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
| | - Susan Yun
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA
| | - Timothy J Welch
- National Center for Cool and Coldwater Aquaculture, Kearneysville, WV 25430, USA
| | | | - Esteban Soto
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA
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Shahin K, Mukkatira K, Yazdi Z, Richey C, Kwak K, Heckman TI, Mohammed HH, Ortega C, Avendaño-Herrera R, Keleher B, Hyatt MW, Drennan JD, Adkison M, Griffin MJ, Soto E. Development of a quantitative polymerase chain reaction assay for detection of the aetiological agents of piscine lactococcosis. J Fish Dis 2022; 45:847-859. [PMID: 35306674 DOI: 10.1111/jfd.13610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 03/01/2022] [Accepted: 03/04/2022] [Indexed: 06/14/2023]
Abstract
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.
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Affiliation(s)
- Khalid Shahin
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
- Aquatic Animal Diseases Laboratory, Aquaculture Department, National Institute of Oceanography and Fisheries, Suez, Egypt
| | | | - Zeinab Yazdi
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Christine Richey
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Kevin Kwak
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Taylor I Heckman
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Haitham H Mohammed
- Department of Aquatic Animal Medicine and Management, Faculty of Veterinary Medicine, Assiut University, Assiut, Egypt
| | - Cesar Ortega
- Centro de Investigación y Estudios Avanzados en Salud Animal (CIESA), Facultad de Medicina Veterinaria y Zootecnia (FMVZ), Universidad Autónoma del Estado de México (UAEM), Toluca, Mexico
| | - Ruben Avendaño-Herrera
- Laboratorio de Patología de Organismos Acuáticos y Biotecnología Acuícola, Universidad Andrés Bello and Centro FONDAP INCAR, Viña del Mar, Chile
| | - Bill Keleher
- Kennebec River Biosciences, Richmond, Maine, USA
| | - Michael W Hyatt
- Wildlife Conservation Society, New York Aquarium, Brooklyn, New York, USA
| | | | - Mark Adkison
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Matt J Griffin
- Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Stoneville, Mississippi, USA
| | - Esteban Soto
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
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Shahin K, Veek T, Heckman TI, Littman E, Mukkatira K, Adkison M, Welch TJ, Imai DM, Pastenkos G, Camus A, Soto E. Isolation and characterization of Lactococcus garvieae from rainbow trout, Onchorhyncus mykiss, from California, USA. Transbound Emerg Dis 2021; 69:2326-2343. [PMID: 34328271 DOI: 10.1111/tbed.14250] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 07/17/2021] [Indexed: 11/26/2022]
Abstract
Lactococcus garvieae is an emergent bacterial pathogen of salmonid fish in North America that causes acute infections particularly at water temperatures above 15°C. During 2020, L. garvieae was detected in rainbow trout, Onchorhyncus mykiss, cultured in Southern California and the Eastern Sierras. Infected fish exhibited high mortalities and nonspecific clinical signs of lethargy, erratic swimming, dark skin pigmentation, and exophthalmia. Macroscopic changes included external and internal hemorrhages, mainly in the eyes, liver, coelomic fat, intestine, and brain. Histological examination revealed splenitis, branchitis, panophthalmitis, hepatitis, enteritis, and coelomitis, with variable degrees of tissue damage among evaluated fish. Pure colonies of L. garvieae were isolated from infected trout and specific PCR primers for L. garvieae confirmed the preliminary diagnosis. Multilocus sequence analysis showed that the strains recovered from diseased trout represent a novel genetic group. Isolates were able to form biofilms within 24 h that increased their resistance to disinfection by hydrogen peroxide. Laboratory challenge methods for inducing lactococcosis in steelhead trout, O. mykiss, were evaluated by intracoelomic injection with serial dilutions of L. garvieae. The median lethal dose 21 days post challenge was ∼20 colony-forming units/fish. Experimentally infected trout presented similar clinical signs, gross changes, and microscopic lesions as those with natural disease, fulfilling Koch's postulates and demonstrating the high virulence of the recovered strains.
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Affiliation(s)
- Khalid Shahin
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA.,Aquatic Animal Diseases Laboratory, Aquaculture Department, National Institute of Oceanography and Fisheries, Suez, Egypt
| | - Tresa Veek
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Taylor I Heckman
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Eric Littman
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | | | - Mark Adkison
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Timothy J Welch
- National Center for Cool and Coldwater Aquaculture, Kearneysville, West Virginia, USA
| | - Denise M Imai
- Comparative Pathology Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Gabrielle Pastenkos
- Comparative Pathology Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Alvin Camus
- Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Esteban Soto
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
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7
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Sebastião FD, Shahin K, Heckman TI, LaFrentz BR, Griffin MJ, Loch TP, Mukkatira K, Veek T, Richey C, Adkison M, Holt RA, Soto E. Genetic characterization of Flavobacterium columnare isolates from the Pacific Northwest, USA. Dis Aquat Organ 2021; 144:151-158. [PMID: 33955853 DOI: 10.3354/dao03588] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Flavobacterium columnare is the causative agent of columnaris disease. Previous work has demonstrated a high degree of genetic variability among F. columnare isolates, identifying 4 genetic groups (GGs) with some host associations. Herein, a total of 49 F. columnare isolates were characterized, the majority of which were collected from 15 different locations throughout the US Pacific Northwest. Most isolates were collected from 2015-2018 and originated from disease outbreaks in salmonid hatcheries and rearing ponds, sturgeon hatcheries and ornamental fish. Other isolates were part of collections recovered from 1980-2018. Initial identification was confirmed by F. columnare species-specific qPCR. Study isolates were further characterized using a multiplex PCR that differentiates between the 4 currently recognized F. columnare GGs. Multiplex PCR results were supported by repetitive sequence-mediated PCR fingerprinting and gyrB sequence analysis. F. columnare GG1 was the most prevalent (83.7%, n = 41/49), represented by isolates from salmonids (n = 32), white sturgeon (n = 2), channel catfish (n = 1), ornamental goldfish (n = 1), koi (n = 3), wild sunfish (n = 1) and 1 unknown host. Six isolates (12.2%, n = 6/49) were identified as GG3, which were cultured from rainbow trout (n = 3) and steelhead trout (n = 3). Two isolates were identified as GG2 (4.1%, n = 2/49) and were from ornamental fish. No GG4 isolates were cultured in this study. The biological significance of this genetic variability remains unclear, but this variation could have significant implications for fish health management. The results from this study provide baseline data for future work developing strategies to ameliorate columnaris-related losses in the US Pacific Northwest.
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Affiliation(s)
- Fernanda de Sebastião
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, California 95616, USA
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8
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Uba U, Martínez-López B, Sebastiao F, Loch T, Knupp C, Mukkatira K, Veek T, Richey C, Adkison M, Griffin M, Soto E. Spatio-temporal evaluation of Flavobacterium psychrophilum genotypes recovered from salmonid hatcheries in California, US. Front Vet Sci 2019. [DOI: 10.3389/conf.fvets.2019.05.00103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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9
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Hedrick RP, McDowelll TS, Gilad O, Adkison M, Bovo G. Systemic herpes-like virus in catfish Ictalurus melas (Italy) differs from Ictalurid herpesvirus 1 (North America). Dis Aquat Organ 2003; 55:85-92. [PMID: 12911055 DOI: 10.3354/dao055085] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A herpesvirus was isolated during 2 occurrences of mass mortality among adult catfish Ictalurus melas raised in different farms in northern Italy. The agent replicated in the channel catfish ovary (CCO) cell line from channel catfish I. punctatus, inducing a cytopathic effect similar to that caused by Ictalurid herpesvirus 1 (also referred to as channel catfish herpesvirus, CCV). The new herpesvirus, designated I. melas herpesvirus (IcmHV) did not react with polyclonal rabbit or monoclonal antibodies directed to CCV in either neutralization or indirect immunofluorescence assays. The virions of IcmHV possessed a hexagonal nucleocapsid of 107 nm in diameter surrounded by an envelope with a diameter of 227 nm (n = 20) typical for members of the family Herpesviridae. Virions of IcmHV purified from infected CCO cells contained 17 polypeptides ranging in size from 17.5 to 175 kDa and most differed in molecular weight from those found for CCV. The IcmHV was also distinct from CCV when compared by restriction fragment length polymorphisms (RFLP) of genomic DNA following digestions with the endonucleases Kpn I and Sac I. Lastly, the virulence of IcmHV for channel catfish fry and juveniles, respectively, was demonstrated by experimental infections induced by bath exposure or intraperitoneal injection that resulted in 78 to 96% cumulative mortality in groups of exposed fish. Preventing the introduction of this agent into geographic regions where significant channel catfish production occurs should be a high priority.
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Affiliation(s)
- Ronald P Hedrick
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California 95616, USA.
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