Treatment of Infected with Ichthyophthirius multifilis Paddlefish (Polyodon spathula Walbaum)

Transcription

1 310 Bulgarian Journal of Agricultural Science, 12 (2006), National Centre for Agrarian Sciences Treatment of Infected with Ichthyophthirius multifilis Paddlefish (Polyodon spathula Walbaum) A. ZAIKOV, T. HUBENOVA and P. VASILEVA Institute of Fisheries and Aquaculture, Varna Branch Plovdiv, BG Plovdiv, Bulgaria Abstract ZAIKOV, A., T. HUBENOVA and P. VASILEVA, Treatment of infected with Ichthophthirius multifilis paddlefish (Polyodon spathula Walbaum). Bulg. J. Agric. Sci.,12: The article points out the results obtained by investigations carried out on treatment of paddlefish Polyodon spathula, infected with ichthyophthirius. The invasion with ichthyophthirius has been registered in paddlefish belonging to two age groups. The first one are fingerlings (2860 pcs with an average body weight of g) and the second are summerlings (83 pcs with an average body weight of and 140 pcs with an average body weight of g). In the first group the treatment was carried out with a solution of sodium chloride at a concentration of 3 ppt (0.3%) and duration of the treatment period of 10 days. In the second group totally 223 pcs of summerlings a short-term bath was carried out with a solution of sodium chloride at a concentration of 50 ppt (5%) with different treatment periods - for 5 minutes (140 pcs) and for 3 minutes (83 pcs) at water temperature of 14 0 С without airing. The investigation showed that to fight ichthyophthiriosis spread among fingerlings of paddlefish (Polyodon spathula) with weight of the long-term bath with a solution of sodium chloride at a concentration of 3 ppt, treatment period of 10 days and water temperature of С could be successfully applied. The repeated short-term baths with a solution of sodium chloride at a concentration of 50 ppt, treatment period of 3 min and water temperature of 14 0 С are an efficient means for treatment of one-summer-old paddlefish invaded by ichthyophthirius. Key words: paddlefish, ichthyophthiriosis, treatment, salt, disease Introduction Paddlefish Polyodon spathula is a representative of sturgeon-like fish, which is in process of acclimatization in Bulgaria. azaikov@yahoo.com The enhanced economic interest show in its cultivation is the reason why over the last couple of years several imports of eggs in eye stage and larvae from various Bulgarian companies have been performed

2 Treatment of Infected with Ichthyophthirius multifilis Paddlefish (Hubenovа et al., 2004). Comparatively good results were achieved as late as in 2004 when it was reared up to one-summer-old age under the mutual cooperation of the Institute of Fisheries and Aquaculture and Beluga AD, Vidin. In the process of acclimatization it has been found out that the successful adaptation of paddlefish to the new conditions of habitation is to a great extent dependent both on its sensitivity to various diseases and on the application of effective treatment measures. According to Graham et al. (1986), Mims et al. (1999), Mims (2001) generally speaking diseases do not represent a major problem when paddlefish is reared in ponds and reservoirs, due most probably to its low density. However, there exist reports on bacterial infections caused by Aeromonas spp. and infection with the parasites Trihodina, Costia, Scyphydia, Ichthyophthirius (Graham et al., 1986; Ford et al., 1994). A detailed list of the established parasites spread among paddlefish upon its rearing in ponds in Europe was provided by Moshu (1998), who reported for 18 ekto and 4 endo-parasites from various taxonomic groups. Massive invasion with Ichthyophthirius spread on two age groups of paddlefish was found out in 2004, namely fingerlings and summerlings reared in the experimental base of the Institute of Fisheries and Aquaculture in Plovdiv. It is a known fact that ichthyophthiriosis is one of the most widely spread and dangerous parasitic infections on fish. It has been established in various species such as carp Cyprinus carpio, sheatfish Silurus glanis, trout Oncorhynchus mykiss, grass carp Ctenopharingodon idella, etc. As far as industrially reared fish are concerned, the disease has been registered quite often and under certain circumstances it could result in considerable losses. The stimulant of the disease is the tassel-like infusoria Ichthyophthirius multifilis, the cycle of development of which has been extensively investigated. Ichthyophthirius is a strongly pathogenic parasite that is particularly dangerous not only for larvae, fingerlings and summerlings, but for fish belonging to other age groups as well. Particularly susceptible to the disease are fish without husky cover such as paddlefish. The registered infection with parasites resulted in experimenting and applying effective treatment measures to fight the dangerous disease, the specific sensitivity of the above species to various manipulations and medicines being taken into consideration. Mims et al. (1999), Mims (2001) report that ichthyophthiriosis on paddlefish is a comparatively frequently registered disease and recommend to fight it with long-term baths with a solution of sodium chloride (3 ppt) in the course of several days (without specifying their exact number) and increasing the temperature up to 30 0 С. Another method for treating ichthyophthiriosis is the widely applied in other species short-term bath, again with sodium chloride, that is not used in paddlefish. The efficiency of the two methods, as well as the comparative safety of the baths with sodium chloride, gave us an adequate motivation to experiment the treatment of the invaded fish by applying long-term and short-term baths with sodium chloride. Material and Methods The invasion by ichthyophthirius has been observed in paddlefish belonging to two age groups. The first one are finger-

3 312 lings (2860 pcs with an average body weight of g) and the second are summerlings (83 pcs with an average weight of and 140 pcs with an average weight of g). In the first case fingerlings are reared in tanks and fed with zooplankton collected from earth ponds that have been stocked with other types of fish (carp and big-head carp). The disease was established on the fingerlings reared in the tanks. In the second group the infection with ichthyophthirius was established in December after the transfer of one-summer-old paddlefish from earth type of pond into tanks. The diagnosis of the disease in both cases has been initially based on a visual observation and then on microscope investigations. Both adult and young forms of the parasite were found on fish. The experiments on treatment of paddlefish are carried out with the two indicated age groups that have been extensively invaded by ichthyophthirius. The treatment was performed with a solution of sodium chloride, the solution concentration and the treatment periods being different for the different age groups. In both cases, prior to the massive treatment of 10 pcs from each age group, a test was carried out on the examination of the tolerability of paddlefish to the relative treatment periods and concentrations of sodium chloride, the behaviour and the survival rate of fish in the course of 24 hours being traced out. In the first group - totally 2860 pcs of fingerlings were distributed in two tanks; the treatment was carried out with a solution of sodium chloride at a concentration of 3 ppt (0.3%) and duration of the treatment period 10 days. The manipulation was made in two standard tanks with dimensions 4 х 1.0 х 0.8 m without water flow. The airing of water was made by micro-compressors, the quantity of the dissolved oxygen and the temperature varying in close limits respectively mg/l and С. On the 5 th day of the treatment the larvae were transferred in two other tanks with clean water and the same concentration of sodium chloride, a total replacement of water being performed. In the second group - totally 223 pcs of summerlings a short-term bath with a solution of sodium chloride was carried out at concentration of 50 ppt (5%) at different treatment periods for 5 minutes (140 pcs) and for 3 minutes (83 pcs) water temperature being 14 0 С without airing. Three days after the first treatment every fish from the two weight groups were secondarily treated at concentration of 50 ppt and a treatment period of 3 min. Baths were carried out in vessels with a volume of 30 l at water temperature of 14 0 С, without airing. Fish were dipped into the solution in groups consisting of pcs, the solution being replaced two-three times during the manipulations. Immediately after the bath the treated species were transferred in tanks with dimensions 4.0 х 1.0 х 0.8 m at a strong water flow of the water and airing with micro-compressor. Results A. Zaikov, T. Hubenova and P. Vasileva The test on the sensitivity of paddlefish to the experimented concentrations and treatment periods that has been preliminarily carried out, showed that fish bear them quite well, no losses being registered. And this was that fact that gave grounds for the undertaking of a massive treatment of the invaded fish. The results achieved and the data on the treatment of the two age groups of paddlefish fingerlings and

4 Treatment of Infected with Ichthyophthirius multifilis Paddlefish Table 1 Salt treatment of infected with Ichthyophthirius multifilis paddlefish Polyodon spathula Age Average body weight, g Fish number Dose NaCl, ppt Treatment period Survival rate, % Fingerlings days Summerlings First min 95.0 treatment min 97.6 Second treatment min summerlings - with a solution of sodium chloride are shown in Table 1. The microscope investigation that has been carried out 10 days after the treatment of the fingerlings showed that they were entirely relieved from parasites. No losses were registered in the course of the experimented period. During the first treatment of summerlings the survival rate is high in both experimented different treatment periods. Comparatively minimal losses were established, 5% and 2.4% respectively at treatment periods of 5 and 3 min. Three days after the baths that were carried out it was found out that there were still individual parasites on the fish, which imposed their secondary treatment. It was performed on all species under the conditions described above, the concentration being 50 ppt and the treatment period being 3 min. A week after the bath it was found out that there were neither young, nor adult forms of ichthyophthirius. Discussion The investigation of the infected with parasites fish from the two age groups shows that ichthyophthirius is located along the whole body of the fish. Parasites are extensively registered on all fins, on the upper and lower part of the rostrum, on the mouth, which imposed the undertaking of urgent treatment measures. The infection of fingerlings with ichthyophthirius has most probably taken place via young forms of the parasite transferred with the water from the pond, the former finding suitable conditions for development at a temperature and high density of fish in the tanks appropriate for them. Fingerlings of paddlefish do not change their behaviour when placed in a solution of sodium chloride at a concentration of 3 ppt, they move smoothly around in their typical way, consuming the food that has been put for them. During the whole treatment period of 10 days no death rate, anxiety acts or any other untypical reaction were registered. Although in the current research the recommended by Mims et al. (1999), Mims (2001) increasing of the temperature up to 30 0 С was not applied, it was confirmed that the long-term bath with sodium chloride at a concentration of 3 ppt is an effective measure for treatment of ichthyophthiriosis.

5 314 Unlike the treatment of fingerlings where the stress is minimal or is practically lacking, summerlings at the high concentration of sodium chloride of 50 ppt undergo strong shock, their behaviour changing considerably. Placed in the treatment solution, their initial reaction is violent, increasing their speed and striving to jump out of the bath. Such a reaction lasts for approximately sec, after which fish become passive, lying laterally or lying on their back performing occasional convulsive movements. Due to the exuberant secretion of mucus their bodies turn white. Having been treated and transferred in the tanks with clean water, considerable water exchange in the course of 2-5 minutes being at hand, they lie on the bottom and then repeatedly try to swim and lie again, gradually resuming their normal behaviour. It is necessary to be noted that the established death rate is registered in fish that have been most extensively invaded by parasites with a deteriorated general status, i.e. they have lost little weight, with acts of billing swimming with their rostrum visible on the surface of the water. Conclusions To fight ichthyophthiriosis spread among fingerlings of paddlefish (Polyodon spathula) with weight of the long-term bath with a solution of sodium chloride at a concentration of 3 ppt, treatment period of 10 days and water temperature of С could be successfully applied. The repeated short-term baths with a solution of sodium chloride at a concentration of 50 ppt, treatment period of 3 min and water temperature of 14 0 С are an efficient means for treatment of one-summer-old paddlefish invaded by ichthyophthirius. References A. Zaikov, T. Hubenova and P. Vasileva Hubenova, Т., А. Zaikov, J. Каranikolov and D. Grozev, First results of paddlefish rearing (Polyodon spathula, Walbaum) in Bulgaria. Animal Sciences, 3: (Bg). Ford, L., R. Ciprino and T. Penniston, Isolation of Aeromonas salmonicia from paddlefish, Polyodon spathula. Journal of Wildlife Diseases, 30 (3): Graham, K., E. Hamilton, T. Russel and C. Hicks, The culture of paddlefish a review of methods. In: J. Dillard, K. Graham and T. Russel (Editors), The paddlefish: status, management and propogation, Modern Litho Print Company, Jefferson City Missouri, USA, pp Mims, S., Aquaculture of paddlefish in the United States. Aquat. Living Resour., 14: Mims, S., W. Shelton, F. Wynne and R. Onders, Production of paddlefish. SRAC Publication, 437: 1-4. Moshu, A., On the parasites fauna of paddlefish (Polyodon spathula) from fish ponds in Europe. Bilding Parthnerships for the 21 st Century (Proceedings of Third International Symposium on Aquatic Animal Health), Baltimor, Maryland, USA, 96 pp.