Wiener Tierärztliche Monatsschrift – Veterinary Medicine Austria 105 (2018) Clinical Division of Fish Medicine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria A fish health survey of selected Austrian rivers: Implications for stocking practices and a wide distri- bution of Tetracapsuloides bryosalmonae E. LEWISCH* and M. EL-MATBOULI received October 10, 2017 accepted February 22, 2018 Keywords: proliferative kidney Schlüsselwörter: Proliferative disease, Tetracapsuloides bryo- Nierenerkrankung, Tetracapsuloides salmonae, monitoring, wild fish, bryosalmonae, Gesundheitsmoni- stocked fish, infectious disease. toring, Wildfische, Fischbesatz, Infektionskrankheit. Summary Zusammenfassung Dabei gelangten 116 Bachforellen, 22 Regenbogenforellen (Oncor- The aim this study was to as- Untersuchung der Fischgesund- hynchus mykiss), elf Aiteln sess the health status of fish, es- heit in ausgewählten österreich- (Squalius cephalus) und ver- pecially brown trout (Salmo trutta), ischen Gewässern: hohe Präva- schiedene andere Fischarten zur in waters where severe decrease lenz von Tetracapsuloides bryo- Untersuchung. Alle Fische wur- of brown trout catches had been salmonae und Auswirkungen den jeweils einer pathoanatomi- observed. Over the course of one von Besatzmaßnahmen schen, parasitologischen, bak- year, 116 brown trout, 22 rain- teriologischen und virologischen bow trout (Oncorhynchus mykiss), Einleitung Untersuchung unterzogen. eleven European chubs (Squalius In verschiedenen Regionen Euro- cephalus) and several speci- pas wird aktuell eine Änderung Ergebnisse mens of other fish were sampled. der aquatischen Fauna und insbe- Die Studie konnte eine wei- Samples were taken each month sondere ein Rückgang der Bach- te Verbreitung des Erregers der and originated from 22 different forellen (Salmo trutta) beobachtet. Proliferativen Nierenerkrankung sites along 15 rivers. All fish un- Dabei liegen zahlreiche Untersu- (PKD) in den untersuchten derwent necropsy, including par- chungen zum Einfluss von verän- Flüssen nachweisen. Darüber hin- asitological, bacterial, and viral derten Umweltbedingungen und aus konnten der Erreger der Viralen examination. The most relevant dem Besatz mit genetisch unpas- Hämorrhagischen Septikämie aus finding was a wide distribution of senden Fischen vor. Im Gegen- einer Regenbogenforelle sowie das Tetracapsuloides bryosalmonae, satz dazu ist der Beitrag von Virus der Infektiösen Pankreasne- the causative agent of proliferative Infektionskrankheiten zum Rück- krose aus fünf Regenbogen- und kidney disease (PKD) (12/22 sites) gang der Populationen kaum un- einer Bachforelle isoliert wer- with high prevalence in the affect- tersucht. In dieser Studie wurde den. Von drei Bachforellen wurde ed waters. One rainbow trout was der Gesundheitszustand von Bach- Aeromonas salmonicida achromo- found to be infected with viral hem- forellen und anderen Wildfischen in genes aus Nierengewebe kultiviert. orrhagic septicemia virus (VHS-V) betroffenen Gewässern erhoben. Parasiten der Haut und der Kiemen and several rainbow trout and wurden bei 6,9 % der Bach- und brown trout were positive for in- Material und Methode 4,5 % der Regenbogenforellen fectious pancreatic necrosis-virus Im Laufe eines Jahres wurden nachgewiesen. Während die- (IPN-V). Three brown trout were monatlich Fische von 22 Entnah- se Parasiten nicht mit pathologi- positive for Aeromonas salmonici- mestellen aus 15 Flüssen beprobt. schen Erscheinungen assoziiert *E-mail: [email protected] 81 Wiener Tierärztliche Monatsschrift – Veterinary Medicine Austria da achromogenes; the bacterium was cultivated from waren, wurden gastrointestinale Läsionen bei mit the head kidney. Infestation with skin and gill parasites Acanthocephalen befallenen Fischen beobachtet. Bei ei- was demonstrated in 6.9 % of brown trout and 4.5 % nigen Bachforellen wurden durch Nematodenbefall her- of rainbow trout. There was no obvious tissue dam- vorgerufene gastrointestinale Granulome nachgewiesen. age caused by these ectoparasites. Infestation with acanthocephales led to gastrointestinal lesions and Schlussfolgerungen even gut perforation in brown trout, European chub, Zum ersten Mal wurde in Österreich eine hohe brook trout (Salvelinus fontinalis) and common barbel Prävalenz von T. bryosalmonae bei Bach- und (Barbus barbus). In several brown trout, granulomas Regenbogenforellen in Freigewässern nachgewie- in the intestinal tract were associated with nematode sen. Darüber hinaus wurden Fälle von Infektionen infection. mit atypischer Furunkulose, VHS und IPN entdeckt. Während für die Verbreitung von T. bryosalmonae Abbreviations: ABOL = Austrian Bar Code of Life; BF = bluegill fry; und somit der PKD Umweltfaktoren eine große Rolle CCB = Cyprinus carpio brain; CHSE = Chinook salmon embryo; COS spielen, ist für die Verbreitung der anderen genann- = Columbia sheep blood; CyHV-3 = Cyprinid herpesvirus-3; IHN = in- ten Infektionserreger der Besatz mit Fischen aus fectious haematopoetic necrosis; IPN = infectious pancreatic necro- sis; MALDI-TOF MS = matrix assisted laser desorption ionization-time Aquakultur maßgeblich verantwortlich. Wir empfehlen of flight mass spectrometry; MEM = Minimal Essential Medium; PKD daher für den Besatz von Freigewässern ausschließ- = proliferative kidney disease; SSU rDNA = small subunit ribosomal lich Fische die nachweislich frei von VHS, IHN und IPN DNA; SVCV = spring viraemia of carp virus VHS = viral haemorrhagic sind zu verwenden. septicaemia; wpi = weeks post infection; Materials and methods Introduction Sampling Brown trout is a widely distributed native species in The sampling period was one year, starting in September 2015. continental Europe with many autochthonous popula- Samples were taken once a month, except for June 2016 when tions. A decline of this fish species has been observed floods occurred. All samples were taken from rivers in the Austrian for several years in many regions (GILES, 1989; ARIAS federal state Upper Austria. In total, 22 sites along 15 rivers were et al., 1995; SCHMIDT et al., 1999; BURKHARDT- sampled. Most of the sampled rivers are situated in a region made of HOLM et al., 2002). Environmental changes, especial- granite and gneiss north to the river Danube (“Mühlviertel”) and enter ly global warming and anthropogenic influence factors, the river Danube, while a few of them drain their waters to the north are discussed as potential causes (BURKHARDT- (Moldova) (details for sampling sites are given in Fig. 1 and Tab. 1). In some rivers, upstream and downstream samples were taken (Fig. 1). HOLM et al., 2002, 2005; BORSUK et al., 2006; Fish were obtained by angling and electro fishing. The number and FILIPE et al., 2013). In Austria, a systematic investiga- species of collected fish as well as frequency of sampling varied con- tion of the anecdotally reported decline of brown trout siderably by site (Fig. 2, Tab. 1) due to the varying fish population in populations has not been carried out. Most rivers are the rivers and organizational issues. Six of the sites were sampled managed by local fishery associations and are stocked regularly, four of which were classical habitats of brown trout, as with trout and other fish on a regular basis. This makes given by history, water temperature and water quality (Tab. 1). Fish it particularly difficult to assess the health state of the were killed by a sharp blow to the head at the collection site and autochthonous fish populations. Reports by the fishery transported to the clinic on ice within 24 hours. managers about a decline of brown trout and the first Gross examination and sampling of fish evidence of Saprolegnia parasitica in Austria (unpub- lished) in the river Feistritz (region "Mühlviertel", feder- Upon arrival, length and weight of each fish were recorded. The al state Upper Austria) prompted fishery managers to body surface was carefully inspected for evidence of skin lesions, initiate the health survey presented in this study. The parasites and fungal infection. Morphological variations were docu- aim of the project was to achieve information about mented. From the dorsolateral surface and the skin region under the left pectoral fin as well as from the dorsal and caudal fins wet mounts the general health condition of wild fish, especially were prepared with a cover glass, spread on a slide together with brown trout. While specific examinations for detection a drop of water and examined with an Olympus BX 53® light micro- of Tetracapsuloides bryosalmonae originally were not scope (Olympus Austria). After removal of the operculum, epithelium part of the project, already the first shipment of sam- from a few gill filaments was scraped and examined as described ples included fish with kidney alterations indicative for for the skin smears. Sex, contents of the gastrointestinal tract and proliferative kidney disease (PKD). Thus, molecular di- any abnormal findings were documented. Cysts, capsules, nodules agnostics for T. bryosalmonae were included for all fol- and other alterations were examined microscopically. The intestinal lowing samples. tract was opened in its entire length and inspected for parasites. Smears from the pyloric caeca region (if applicable), the midgut and the hindgut were prepared. The epiaxal musculature was sliced and inspected for cysts, larval worms and haemorrhages. Other organs were only included in the parasitological examination if suspicious alterations were observed. Parasites were