The population of brown trout (Salmo trutta fario) in continental Europe is on the decline, with infectious diseases confirmed as one of the causative factors. However, no data on the epizootiological situation of wild fish in the Czech Republic are currently available. In this study, brown trout (n = 260) from eight rivers were examined for the presence of viral and parasitical pathogens. Salmonid alphavirus-2, infectious pancreatic necrosis virus, piscine novirhabdovirus (VHSV) and salmonid novirhabdovirus (IHNV) were not detected using PCR. Cell culturing showed no viruses as well, and serological analysis of 110 sera did not detect any specific antibodies against VHSV or IHNV. Fish from two rivers were positive for the presence of piscine orthoreovirus-3 (PRV-3), subtype PRV-3b. However, none of the PRV-3-positive fish showed gross pathologies typically associated with PRV infections. By far the most widespread pathogen was Tetracapsuloides bryosalmonae which was confirmed in each of the examined locations, with a prevalence of up to 65% and 100%, as established by immunohistochemistry and PCR, respectively. Furthermore, up to 43.8% of fish showed signs of proliferative kidney disease caused by T. bryosalmonae, suggesting that this parasite is a main health challenge for brown trout in the Czech Republic.

Department of Ecology and Diseases of Zooanimals Game Fish and Bees Veterinary and Pharmaceutical University 612 42 Brno Czech Republic

Department of Immunology Veterinary Research Institute 621 00 Brno Czech Republic

Department of Virology Veterinary Research Institute 621 00 Brno Czech Republic

Department of Zoology Fisheries Hydrobiology and Apiculture Mendel University 613 00 Brno Czech Republic

Fish Disease Research Unit Institute for Parasitology University of Veterinary Medicine 30559 Hannover Germany

Zobrazit více v PubMed

Ministry of Agriculture of the Czech Republic State of the Czech Argiculture. [(accessed on 27 June 2020)]; Available online: http://eagri.cz/public/web/file/648258/Zelena_zprava_2018.pdf.

OIE OIE-Listed Diseases, Infections and Infestations in Force in 2020. [(accessed on 27 June 2020)]; Available online: https://www.oie.int/animal-health-in-the-world/oie-listed-diseases-2020/

Reichert M., Matras M., Skall H.F., Olesen N.J., Kahns S. Trade practices are main factors involved in the transmission of viral haemorrhagic septicaemia. J. Fish Dis. 2013;36:103–114. doi: 10.1111/jfd.12004. PubMed DOI

European Commission Animal Disease Notification System (ADNS) [(accessed on 27 June 2020)]; Available online: https://ec.europa.eu/food/animals/animal-diseases/not-system_en.

Pojezdal Ľ., Pokorová D., Reschová S., Palíková M., Vícenová M., Veselý T., Navrátil S. Diagnostic efficacy of molecular assays for the viral haemorrhagic septicaemia virus isolates from the Czech Republic. Acta Vet. Brno. 2017;86:207–212. doi: 10.2754/avb201786030207. DOI

Kahns S., Skall H.F., Kaas R.S., Korsholm H., Bang Jensen B., Jonstrup S.P., Dodge M.J., Einer-Jensen K., Stone D., Olesen N.J. European freshwater VHSV genotype Ia isolates divide into two distinct subpopulations. Dis. Aquat. Org. 2012;99:23–35. doi: 10.3354/dao02444. PubMed DOI

Gadd T., Jakava-Viljanen M., Einer-Jensen K., Ariel E., Koski P., Sihvonen L. Viral haemorrhagic septicaemia virus (VHSV) genotype II isolated from European river lamprey Lampetra fluviatilis in Finland during surveillance from 1999 to 2008. Dis. Aquat. Org. 2010;88:189–198. doi: 10.3354/dao02169. PubMed DOI

Knuesel R., Segner H., Wahli T. A survey of viral diseases in farmed and feral salmonids in Switzerland. J. Fish Dis. 2003;26:167–182. doi: 10.1046/j.1365-2761.2003.00447.x. PubMed DOI

Skall H.F., Olesen N.J., Mellergaard S. Viral haemorrhagic septicaemia virus in marine fish and its implications for fish farming—A review. J. Fish Dis. 2005;28:509–529. doi: 10.1111/j.1365-2761.2005.00654.x. PubMed DOI

Wallace I.S., McKay P., Murray A.G. A historical review of the key bacterial and viral pathogens of Scottish wild fish. J. Fish Dis. 2017;40:1741–1756. doi: 10.1111/jfd.12654. PubMed DOI

Elsayed E., Faisal M., Thomas M., Whelan G., Batts W., Winton J. Isolation of viral haemorrhagic septicaemia virus from muskellunge, Esox masquinongy (Mitchill), in Lake St Clair, Michigan, USA reveals a new sublineage of the North American genotype. J. Fish Dis. 2006;29:611–619. doi: 10.1111/j.1365-2761.2006.00755.x. PubMed DOI

Ammayappan A., Vakharia V.N. Molecular characterization of the Great Lakes viral hemorrhagic septicemia virus (VHSV) isolate from USA. Virol. J. 2009;6:171. doi: 10.1186/1743-422X-6-171. PubMed DOI PMC

Kurath G., Garver K.A., Troyer R.M., Emmenegger E.J., Einer-Jensen K., Anderson E.D. Phylogeography of infectious haematopoietic necrosis virus in North America. J. Gen. Virol. 2003;84:803–814. doi: 10.1099/vir.0.18771-0. PubMed DOI

Rexhepi A., Berxholi K., Scheinert P., Hamidi A., Sherifi K. Study of viral diseases in some freshwater fish in the Republic of Kosovo. Veterinarski Arhiv. 2011;81:405–413.

Bellec L., Louboutin L., Cabon J., Castric J., Cozien J., Thiery R., Morin T. Molecular evolution and phylogeography of infectious hematopoietic necrosis virus with a focus on its presence in France over the last 30 years. J. Gen. Virol. 2017;98:2438–2446. doi: 10.1099/jgv.0.000894. PubMed DOI

Olsen A.B., Hjortaas M., Tengs T., Hellberg H., Johansen R. First description of a new disease in rainbow trout (Oncorhynchus mykiss (Walbaum)) similar to Heart and Skeletal Muscle Inflammation (HSMI) and detection of a gene sequence related to Piscine Orthoreovirus (PRV) PLoS ONE. 2015;10:e0131638. doi: 10.1371/journal.pone.0131638. PubMed DOI PMC

Vendramin N., Kannimuthu D., Olsen A.B., Cuenca A., Teige L.H., Wessel O., Iburg T.M., Dahle M.K., Rimstad E., Olesen N.J. Piscine orthoreovirus subtype 3 (PRV-3) causes heart inflammation in rainbow trout (Oncorhynchus mykiss) Vet. Res. 2019;50:14. doi: 10.1186/s13567-019-0632-4. PubMed DOI PMC

Adamek M., Hellmann J., Flamm A., Teitge F., Vendramin N., Fey D., Risse K., Blakey F., Rimstad E., Steinhagen D. Detection of piscine orthoreoviruses (PRV-1 and PRV-3) in Atlantic salmon and rainbow trout farmed in Germany. Transbound. Emerg. Dis. 2019;66:14–21. doi: 10.1111/tbed.13018. PubMed DOI

Dhamotharan K., Vendramin N., Markussen T., Wessel O., Cuenca A., Nyman I.B., Olsen A.B., Tengs T., Krudtaa Dahle M., Rimstad E. Molecular and antigenic characterization of Piscine orthoreovirus (PRV) from rainbow trout (Oncorhynchus mykiss) Viruses. 2018;10:170. doi: 10.3390/v10040170. PubMed DOI PMC

Cartagena J., Tambley C., Sandino A.M., Spencer E., Tello M. Detection of piscine orthoreovirus in farmed rainbow trout from Chile. Aquaculture. 2018;493:79–84. doi: 10.1016/j.aquaculture.2018.04.044. DOI

Kuehn R., Stoeckle B.C., Young M., Popp L., Taeubert J.E., Pfaffl M.W., Geist J. Identification of a piscine reovirus-related pathogen in proliferative darkening syndrome (PDS) infected brown trout (Salmo trutta fario) using a next-generation technology detection pipeline. PLoS ONE. 2018;13:e0206164. doi: 10.1371/journal.pone.0206164. PubMed DOI PMC

Lahnsteiner F., Haunschmid R., Mansour N. Possible reasons for late summer brown trout (Salmo trutta Linnaeus 1758) mortality in Austrian prealpine river systems. J. Appl. Ichthyol. 2011;27:83–93. doi: 10.1111/j.1439-0426.2010.01621.x. DOI

Fux R., Arndt D., Langenmayer M.C., Schwaiger J., Ferling H., Fischer N., Indenbirken D., Grundhoff A., Dolken L., Adamek M., et al. Piscine Orthoreovirus 3 is not the causative pathogen of Proliferative Darkening Syndrome (PDS) of brown trout (Salmo trutta fario) Viruses. 2019;11:112. doi: 10.3390/v11020112. PubMed DOI PMC

Arndt D., Fux R., Blutke A., Schwaiger J., El-Matbouli M., Sutter G., Langenmayer M.C. Proliferative kidney disease and proliferative darkening syndrome are linked with brown trout (Salmo trutta fario) mortalities in the Pre-Alpine Isar River. Pathogens. 2019;8:177. doi: 10.3390/pathogens8040177. PubMed DOI PMC

Lewisch E., Unfer G., Pinter K., Bechter T., El-Matbouli M. Distribution and prevalence of T. bryosalmonae in Austria: A first survey of trout from rivers with a shrinking population. J. Fish Dis. 2018;41:1549–1557. doi: 10.1111/jfd.12863. PubMed DOI

Hedrick R.P., MacConnell E., de Kinkelin P. Proliferative kidney disease of salmonid fish. Annu. Rev. Fish Dis. 1993;3:277–290. doi: 10.1016/0959-8030(93)90039-E. DOI

Palikova M., Papezikova I., Markova Z., Navratil S., Mares J., Mares L., Vojtek L., Hyrsl P., Jelinkova E., Schmidt-Posthaus H. Proliferative kidney disease in rainbow trout (Oncorhynchus mykiss) under intensive breeding conditions: Pathogenesis and haematological and immune parameters. Vet. Parasitol. 2017;238:5–16. doi: 10.1016/j.vetpar.2017.03.003. PubMed DOI

European Commission Commission Implementing Decision (EU) 2015/1554 of 11 September 2015 Laying Down Rules for the Application of Directive 2006/88/EC as Regards Requirements for Surveillance and Diagnostic Methods. [(accessed on 27 June 2020)]; Available online: http://data.europa.eu/eli/dec_impl/2015/1554/oj.

Jørgensen P.E.V. Egtved virus: The susceptibility of brown trout and rainbow trout to eight virus isolates and the significance of the findings for the VHS control. Fish Dis. 1980:3–7. doi: 10.1007/978-3-642-67854-7_1. DOI

Abbadi M., Fusaro A., Ceolin C., Casarotto C., Quartesan R., Dalla Pozza M., Cattoli G., Toffan A., Holmes E.C., Panzarin V. Molecular evolution and phylogeography of co-circulating IHNV and VHSV in Italy. Front. Microbiol. 2016;7:1306. doi: 10.3389/fmicb.2016.01306. PubMed DOI PMC

Dixon P.F., Avery S., Chambers E., Feist S., Mandhar H., Parry L., Stone D.M., Strommen H.K., Thurlow J.K., Lui C.T., et al. Four years of monitoring for viral haemorrhagic septicaemia virus in marine waters around the United Kingdom. Dis. Aquat. Org. 2003;54:175–186. doi: 10.3354/dao054175. PubMed DOI

Dopazo C.P., Moreno P., Olveira J.G., Borrego J.J. The theoretical reliability of PCR-based fish viral diagnostic methods is critically affected when they are applied to fish populations with low prevalence and virus loads. J. Appl. Microbiol. 2018;124:977–989. doi: 10.1111/jam.13586. PubMed DOI

Fringuelli E., Rowley H.M., Wilson J.C., Hunter R., Rodger H., Graham D.A. Phylogenetic analyses and molecular epidemiology of European salmonid alphaviruses (SAV) based on partial E2 and nsP3 gene nucleotide sequences. J. Fish Dis. 2008;31:811–823. doi: 10.1111/j.1365-2761.2008.00944.x. PubMed DOI

State Veterinary Administration Disease Status of Fish in the Czech Republic. [(accessed on 27 June 2020)]; Available online: https://www.svscr.cz/zdravi-zvirat/zdravi-ryb/nakazova-situace-v-cr/

Madhun A.S., Isachsen C.H., Omdal L.M., Einen A.C.B., Bjorn P.A., Nilsen R., Karlsbakk E. Occurrence of Salmonid Alphavirus (SAV) and Piscine Orthoreovirus (PRV) infections in wild sea trout Salmo trutta in Norway. Dis. Aquat. Org. 2016;120:109–113. doi: 10.3354/dao03009. PubMed DOI

Vendramin N., Alencar A.L.F., Iburg T.M., Dahle M.K., Wessel O., Olsen A.B., Rimstad E., Olesen N.J. Piscine orthoreovirus infection in Atlantic salmon (Salmo salar) protects against subsequent challenge with infectious hematopoietic necrosis virus (IHNV) Vet. Res. 2018;49:30. doi: 10.1186/s13567-018-0524-z. PubMed DOI PMC

Gorgoglione B., Taylor N.G.H., Holland J.W., Feist S.W., Secombes C.J. Immune response modulation upon sequential heterogeneous co-infection with Tetracapsuloides bryosalmonae and VHSV in brown trout (Salmo trutta) Fish Shellfish Immunol. 2019;88:375–390. doi: 10.1016/j.fsi.2019.02.032. PubMed DOI

Schmidt-Posthaus H., Steiner P., Muller B., Casanova-Nakayama A. Complex interaction between proliferative kidney disease, water temperature and concurrent nematode infection in brown trout. Dis. Aquat. Org. 2013;104:23–34. doi: 10.3354/dao02580. PubMed DOI

Clifton-Hadley R.S., Bucke D., Richards R.H. Proliferative kidney disease of salmonid fish: A review. J. Fish Dis. 1984;7:363–377. doi: 10.1111/j.1365-2761.1984.tb01201.x. DOI

Grabner D.S., El-Matbouli M. Comparison of the susceptibility of brown trout (Salmo trutta) and four rainbow trout (Oncorhynchus mykiss) strains to the myxozoan Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease (PKD) Vet. Parasitol. 2009;165:200–206. doi: 10.1016/j.vetpar.2009.07.028. PubMed DOI

Wahli T., Knuesel R., Bernet D., Segner H., Pugovkin D., Burkhardt-Holm P., Escher M., Schmidt-Posthaus H. Proliferative kidney disease in Switzerland: Current state of knowledge. J. Fish Dis. 2002;25:491–500. doi: 10.1046/j.1365-2761.2002.00401.x. DOI

Wahli T., Bernet D., Steiner P.A., Schmidt-Posthaus H. Geographic distribution of Tetracapsuloides bryosalmonae infected fish in Swiss rivers: An update. Aquat. Sci. 2007;69:3–10. doi: 10.1007/s00027-006-0843-4. DOI

Rubin A., de Coulon P., Bailey C., Segner H., Wahli T., Rubin J.F. Keeping an eye on wild brown trout (Salmo trutta) populations: Correlation between temperature, environmental parameters, and proliferative kidney disease. Front. Vet. Sci. 2019;6:281. doi: 10.3389/fvets.2019.00281. PubMed DOI PMC

Peeler E.J., Feist S.W., Longshaw M., Thrush M.A., St-Hilaire S. An assessment of the variation in the prevalence of renal myxosporidiosis and hepatitis in wild brown trout, Salmo trutta L.; within and between rivers in South-West England. J. Fish Dis. 2008;31:719–728. doi: 10.1111/j.1365-2761.2008.00942.x. PubMed DOI

Dash M., Vasemagi A. Proliferative kidney disease (PKD) agent Tetracapsuloides bryosalmonae in brown trout populations in Estonia. Dis. Aquat. Org. 2014;109:139–148. doi: 10.3354/dao02731. PubMed DOI

Abd-Elfattah A., Kumar G., Soliman H., El-Matbouli M. Persistence of Tetracapsuloides bryosalmonae (Myxozoa) in chronically infected brown trout Salmo trutta. Dis. Aquat. Org. 2014;111:41–49. doi: 10.3354/dao02768. PubMed DOI PMC

Soliman H., Kumar G., El-Matbouli M. Tetracapsuloides bryosalmonae persists in brown trout Salmo trutta for five years post exposure. Dis. Aquat. Org. 2018;127:151–156. doi: 10.3354/dao03200. PubMed DOI

Kumar G., Sarker S., Menanteau-Ledouble S., El-Matbouli M. Tetracapsuloides bryosalmonae infection affects the expression of genes involved in cellular signal transduction and iron metabolism in the kidney of the brown trout Salmo trutta. Parasitol. Res. 2015;114:2301–2308. doi: 10.1007/s00436-015-4425-z. PubMed DOI PMC

Bailey C., Strepparava N., Wahli T., Segner H. Exploring the immune response, tolerance and resistance in proliferative kidney disease of salmonids. Dev. Comp. Immunol. 2019;90:165–175. doi: 10.1016/j.dci.2018.09.015. PubMed DOI

Borsuk M.E., Reichert P., Peter A., Schager E., Burkhardt-Holm P. Assessing the decline of brown trout (Salmo trutta) in Swiss rivers using a Bayesian probability network. Ecol. Model. 2006;192:224–244. doi: 10.1016/j.ecolmodel.2005.07.006. DOI

Schmidt-Posthaus H., Bernet D., Wahli T., Burkhardt-Holm P. Morphological organ alterations and infectious diseases in brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss exposed to polluted river water. Dis. Aquat. Org. 2001;44:161–170. doi: 10.3354/dao044161. PubMed DOI

Zimmerli S., Bernet D., Burkhardt-Holm P., Schmidt-Posthaus H., Vonlanthen P., Wahli T., Segner H. Assessment of fish health status in four Swiss rivers showing a decline of brown trout catches. Aquat. Sci. 2007;69:11–25. doi: 10.1007/s00027-006-0844-3. DOI

Wahli T., Bernet D., Segner H., Schmidt-Posthaus H. Role of altitude and water temperature as regulating factors for the geographical distribution ofTetracapsuloides bryosalmonaeinfected fishes in Switzerland. J. Fish Biol. 2008;73:2184–2197. doi: 10.1111/j.1095-8649.2008.02054.x. DOI

Cinkova K., Reschová S., Kulich P., Veselý T. Evaluation of a polyclonal antibody for the detection and identification of ranaviruses from freshwater fish and amphibians. Dis. Aquat. Org. 2010;89:191–198. doi: 10.3354/dao02198. PubMed DOI

Farr A.G., Nakane P.K. Immunohistochemistry with enzyme labeled antibodies: A brief review. J. Immunol. Methods. 1981;47:129–144. doi: 10.1016/0022-1759(81)90114-9. PubMed DOI

Dereeper A., Guignon V., Blanc G., Audic S., Buffet S., Chevenet F., Dufayard J.F., Guindon S., Lefort V., Lescot M., et al. Phylogeny.fr: Robust phylogenetic analysis for the non-specialist. Nucleic Acids Res. 2008;36:465–469. doi: 10.1093/nar/gkn180. PubMed DOI PMC

Dietrich M.A., Nynca J., Adamek M., Steinhagen D., Karol H., Ciereszko A. Expression of apolipoprotein A-I and A-II in rainbow trout reproductive tract and their possible role in antibacterial defence. Fish Shellfish Immunol. 2015;45:750–756. doi: 10.1016/j.fsi.2015.05.048. PubMed DOI

Jonstrup S.P., Kahns S., Skall H.F., Boutrup T.S., Olesen N.J. Development and validation of a novel Taqman-based real-time RT-PCR assay suitable for demonstrating freedom from viral haemorrhagic septicaemia virus. J. Fish Dis. 2013;36:9–23. doi: 10.1111/j.1365-2761.2012.01416.x. PubMed DOI

Purcell M.K., Thompson R.L., Garver K.A., Hawley L.M., Batts W.N., Sprague L., Sampson C., Winton J.R. Universal reverse-transcriptase real-time PCR for infectious hematopoietic necrosis virus (IHNV) Dis. Aquat. Org. 2013;106:103–115. doi: 10.3354/dao02644. PubMed DOI

Orpetveit I., Mikalsen A.B., Sindre H., Evensen O., Dannevig B.H., Midtlyng P.J. Detection of infectious pancreatic necrosis virus in subclinically infected Atlantic salmon by virus isolation in cell culture or real-time reverse transcription polymerase chain reaction: Influence of sample preservation and storage. J. Vet. Diagn. Investig. 2010;22:886–895. doi: 10.1177/104063871002200606. PubMed DOI

Hodneland K., Endresen C. Sensitive and specific detection of Salmonid alphavirus using real-time PCR (TaqMan) J. Virol. Methods. 2006;131:184–192. doi: 10.1016/j.jviromet.2005.08.012. PubMed DOI

Bettge K., Segner H., Burki R., Schmidt-Posthaus H., Wahli T. Proliferative kidney disease (PKD) of rainbow trout: Temperature- and time-related changes of Tetracapsuloides bryosalmonae DNA in the kidney. Parasitology. 2009;136:615–625. doi: 10.1017/S0031182009005800. PubMed DOI

Adams A., Richards R.H., Mateo M.M. Development of monoclonal antibodies to PK‘X’, the causative agent of proliferative kidney disease. J. Fish Dis. 1992;15:515–521. doi: 10.1111/j.1365-2761.1992.tb00683.x. DOI

Schmidt-Posthaus H., Bettge K., Forster U., Segner H., Wahli T. Kidney pathology and parasite intensity in rainbow trout Oncorhynchus mykiss surviving proliferative kidney disease: Time course and influence of temperature. Dis. Aquat. Org. 2012;97:207–218. doi: 10.3354/dao02417. PubMed DOI

Nephrocalcinosis in farmed salmonids: diagnostic challenges associated with low performance and sporadic mortality

Comparison of diagnostic methods for Tetracapsuloides bryosalmonae detection in salmonid fish