Infection by Capriniana piscium (Buetschli, 1889) Jankovski, 1973, a cause of rainbow trout (Oncorhynchus mykiss) kill

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1 Bull. Eur. Ass. Fish Pathol., 29(3) 2009, 92 Infection by Capriniana piscium (Buetschli, 1889) Jankovski, 1973, a cause of rainbow trout (Oncorhynchus mykiss) kill Z. Svobodová 1,2, J. Kolářová 1*, I. Dyková 3, J. Hamáčková 1 and J. Kouřil 1 1 University of South Bohemia, České Budějovice, Research Institute of Fish Culture and Hydrobiology, Vodňany, Czech Republic; 2 University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic; 3 Institute of Parasitology, Academy of Sciences of the Czech Republic, České Budějovice, Czech Republic Abstract The aim of this contribution is to describe an infection by the ciliate ectocommensal Capriniana piscium as a possible cause of rainbow trout (Oncorhynchus mykiss) kill in an intensive culture. A relatively dense stock ( kg.m -3 ) combined with unfavourable physical and chemical parameters of water in rearing troughs are described as predisposition factors for the outbreak of the infection. A period of several days of a high water temperature (i.e o C), along with a higher ph and a lower oxygen concentration, is considered the main predisposition factor for rainbow trout capriniosis. Bacteriological, virological and parasitological examinations did not suggest involvement of any other component cause of this infection. Introduction Capriniana piscium (Buetschli, 1889) Jankovski, 1973, syn. Trichophrya piscinum Buetschli, 1889 (Figure. 1) is an ectocommensal of various species of freshwater fishes of Eurasia and North America. It may be abundant in cold as well as warm periods of the year, depending on the condition of the host (Lom, 1971). Ergens and Lom (1970), Rahkonen (1994) and Halmetoja et al. (2000) detected C. piscium mainly in perch (Perca fluviatilis). It was also found in pike (Esox lucius) by Ergens and Lom (1970), Lom and Dyková (1992), and Prost (1989); in silurids by Ergens and Lom (1970), Prost (1989) and Stoskopf (1993); in grayling (Thymallus arcticus) stocked into Michigan lakes by Muzzall (1990); in common and blue bream (Abramis brama and A. ballerus) from Dabie Lake in Poland by Wierzbicka (1997a,b); and in European smelt (Osmerus eperlanus) in the Sjamozero Lake in Karelia by Evseeva et al. (1999). Hofer et al. (2005) did not directly correlate tissue damage caused by C. piscium on gills of arctic char (Salvelinus alpinus) with physical and chemical parameters in an oligotrophic high mountain lake (Oberer Plenderlesee, Austria). There the maximum abundance of C. piscium (heavy infection) was reported in autumn and early winter and the minimum abundance between winter and summer. Capriniosis was observed also in salmonids * Corresponding author s kolarova@vurh.jcu.cz

2 Bull. Eur. Ass. Fish Pathol., 29(3) 2009, 93 8 laminated troughs of 1 m 3 water volume each from March 25 to June 23, with a goal to test production effectiveness of several good-quality pelleted feeds for salmonids. Water to the troughs was pumped from a pond supplied from the Blanice River at Vodňany (South Bohemia, Czech Republic). A permanent water flow-through ensured water exchange approximately two times per hour. The experiment was divided into four particular rearing periods (Figure 4). Figure 1. Capriniana piscium. (900x magnification). (Ergens and Lom, 1970; Prost, 1989; Bruno and Poppe, 1996; Buchmann and Bresciani, 1997; Mamontova et al., 2005; Muzzall, 1990, 2000). Isaksen (2003) observed five genera of protozoan symbionts on the skin or gills of the farmed salmon. The suctorian ciliate Capriniana piscium infected the gill lamella (rarely skin) heavily in July the prevalence of infection was equal or close to 100%. C. piscium seems to be a harmless commensal, and it may be a useful indicator of aspects pertaining to water quality. The aim of this contribution is to introduce infection by the ciliate ectocommensal C. piscium as a possible cause of rainbow trout (Oncorhynchus mykiss) kill in an intensive culture and to evaluate predisposition factors for outbreaks of this infection. Material and Methods The experimental fish was rainbow trout (Oncorhynchus mykiss). Fish were reared in Initial rainbow trout stock in individual troughs was 7.5 kg.m -3 (i.e. 50 fish per m 3 a t 150 g mean individual body weight). At the end of experiment, mean individual body weight in individual troughs ranged in g, representing kg.m -3 stock biomass. Fish were fed manually two times per day. Feeding rates were determined in relation to the actual stock biomass and water temperature. During the last rearing period (June 5 June 23), the mean daily feeding rate represented 0.8% of the actual fish biomass. During the entire experiment, temperature of the inflowing water was registered daily at 8.00 a.m. Temperature of outflowing water as well as dissolved oxygen concentration were registered daily in all troughs at 2.00 p.m. Others physical parameters of water were measured in inflowing water samples taken once per week at 8.00 a.m. On June 13, 17 and 23, fish health examination focused on bacteriological, virological and parasitological parameters were performed, based on occurring rainbow trout kills. Native preparations of fins, skin and gills

3 Bull. Eur. Ass. Fish Pathol., 29(3) 2009, 94 Figure 2. Capriniana piscium in rainbow trout gills. were examined. Altogether 61 fish randomly sampled from all troughs were examined and prevalence and intensity of parasitic infection were determined. Infection intensity was assessed as solitary (below 3 protozoan parasites per microscopic field), medium strong (3-10 protozoan parasites per microscopic field) or strong (11-30 protozoan parasites per microscopic field). In all cases, objective and eyepiece magnifications were 10x and 6x, respectively. Results and Discussion In the first three particular rearing periods (March 25 June 4), fish mortality was registered only rarely. During the last rearing period (June 5 June 23), however, there was 22% mortality in one of the troughs along with 2-8% mortality in another five troughs. No fish mortality was registered in two troughs. Moreover, other production parameters observed (i.e. weight gain and feed conversion ratio) decreased during the last rearing period, too. A fish kill was first registered in one of the troughs on June 13. The next day, five rainbow Figure 3. Capriniana piscium in rainbow trout gills. trout of 250 g body weight, staying close to the surface and not reacting in a usual manner, sampled from different troughs, were examined. Capriniana piscium was found in a strong intensity on gills of all these fish and in a solitary to medium strong intensity on their fins and skin. A solitary fish kill in some troughs was registered on June 15. On June 17, two fish per trough were examined, i.e. in total 16 fish with body weight ranging in g. Prevalence of C. piscium was 100%; the infection intensity was medium strong on gills and solitary on fins and skin. Ten days after the first fish kill observed, on June 23, five fish per trough (40 fish in total) were examined when terminating and evaluating the feeding experiment. Fish weight ranged in g. The prevalence of C. piscium was 100%; the infection intensity was solitary. In all examinations, the finding of C. piscium was stronger on gills (Figure 2 and 3) compared to that on fins and skin. No difference in prevalence and infection intensity among rainbow trout from different troughs was registered either on June 17 or June 23. All fish examined were in a very good nutritive

4 Bull. Eur. Ass. Fish Pathol., 29(3) 2009, 95 Figure 4. Values of dissolved oxygen and water temperature (x±sd) on outflow from the troughs at 2.00 p.m Beginning of rainbow trout kill in individual troughs.

5 Bull. Eur. Ass. Fish Pathol., 29(3) 2009, 96 condition and without pathological alterations. Results of bacteriological, virological and parasitological examinations revealed no other component cause of the kill observed. We assume that a relatively high stocking density ( kg.m -3 ), intensive feeding that resulted in a high water load of organic substances, and, above all, values of physical and chemical water parameters that are less favourable for trout (Svobodová et al., 1993), contributed significantly to the infection outbreak in the last rearing period. During June the temperature of the outflowing water registered daily in all troughs at 2.00 p.m. was o C (Figure 4). The temperature of the inflowing water registered daily at 8.00 a.m. was slightly lower but it ranged in o C during the critical period of June Such temperature conditions, unfavourable for rainbow trout, can be considered the main predisposition factor for the capriniosis outbreak. This assumption is supported by the decrease of infection intensity between June 17-23, when the water temperature decreased as well (outflowing water at 2.00 p.m.: 15: o C; inflowing water at 8.00 a.m.: o C). Apart from water temperature, increased ph values and a lower concentration of dissolved oxygen (Figure 4) could also have contributed to the weakening of rainbow trout (Pechar, 2000). The ph values in inflowing water samples taken at 8.00 a.m. ranged in during the last rearing period. As the troughs were supplied with water from a pond, ph values approx could be anticipated during afternoon hours at this time of the year. The values of dissolved oxygen concentration registered in outflowing water at 2.00 p.m. are shown in Figure. 4. A significant decrease in oxygen concentration in water occurred after May 27 and lowered oxygen concentrations appeared till the end of the experiment. Moreover, a daily fluctuation of dissolved oxygen values in the pond inflowing water should be taken into account same as ph values: even lower concentrations of dissolved oxygen in the rearing troughs could be expected during night and morning hours. Acknowledgements: This research was supported by the Ministry of Education, Youth and Sports of the Czech Republic (MSM Project No and MSM Project No ). References Bruno DW & Poppe TT (1996). A colour atlas of salmonid diseases. Academic Press Limited, London, 194 pp. Buchmann K & Bresciani J (1997). Parasitic infections in pond-reared rainbow trout Oncorhynchus mykiss in Denmark. Diseases of Aquatic Organisms 28 (2), Ergens R & Lom, J (1970). Původci parazitárních nemocí ryb. Academia Praha, 383 pp. Evseeva NV, Leshko EP & Shulman BS (1999). The role of acclimatization in the formation of parasite fauna in the European smelt Osmerus eperlanus in the Sjamozero lake (Karelia). Parazitologiya 33(5), Halmetoja A, Valtonen ET & Koskenniemi E (2000). Perch (Perca fluviatilis L.) parasites reflect ecosystem conditions of natural lake and two acidic reservoirs in Finland. International Journal for Parasitology 30(14), Hofer R, Salvenmoser W & Fried J (2005).

6 Bull. Eur. Ass. Fish Pathol., 29(3) 2009, 97 Population dynamics of Capriniana piscium (Ciliophora, Suctoria) on the gill of Arctic char (Salvelinus alpinus) from high mountain lakes. Archiv fũr Hydrobiologie 162(1), Isaksen TE (2003). Protozoan ectosymbionts on Atlantic salmon (Salmo salar L.) in a hatchery in Hordaland, western Norway: morphology and epizootology. ISBN til elektronisk utgave: Lom J (1971). Trichophrya piscium: a pathogen or an ectocommensal? An ultrastructural study. Folia parasitologica 18, Lom J & Dyková I (1992). Protozoan parasites of fishes. Elsevier, Amsterdam, 328 pp. Svobodová Z, Loyd R, Máchová J & & Vykusová B (1993). Water quality and fish health.. EIFAC Technical Paper Rome 54, 67pp. Wierzbicka J (1997a). Ciliates (Ciliophora) parasitic on the gills of the blue bream, Abramis ballerus (L.) from Dabie lake (Poland). Acta ichthyologica et piscatoria 27(2), Wierzbicka J (1997b). Parasitic ciliates (Protozoa, Ciliophora) of the common bream, Abramis brama (L.) and white bream Blicca bjoerkna (L.), from Dabie lake (Poland). Acta ichthyologica et piscatoria 27(2), Mamontova OV, Rumjancev EA & Šulman BS (2005). Ob osobennostjach parazitofauny palii vodojemov basejnov Baltijskogo i Belogo morej. Materialy IX. meždunarodnoj konferencii , Petrozavodsk, Karelija. Russia. C., Muzzall PM (1990). Parasites of arctic grayling, Thymallus arcticus (Pallas), stocked into Michigan lakes. Canadian Journal of Zoology 68(3), Muzzall PM (2000). Parasite of farmraised trout in Michigan, USA. Comparative Parasitology 67(2), Pechar L (2000). Impacts of long-term changes in fishery management on the trophic level water quality in Czech fish ponds. Fisheries Management and Ecology 7, Prost M (1989). Choroby ryb. Panstwowe Wyd. Polnicze i Lesne, Warszawa, 459 pp. Rahkonen R (1994). Parasites of pike perch Stizostedion luciopera (Linnaeus 1758) fry reared in two different types of natural food ponds in southern Finland. Aquaculture 122 (4), Stoskopf MK (1993). Fish medicine. W.B. Sounders Company Philadelphia, 882 p.