View metadata, citation and similar papers at core.ac.uk brought to you by CORE

provided by Wageningen University & Research Publications

Bull. Eur. Ass. Fish Pathol., 23(4) 2003, 152 Praziquantel treatment of captive white- spotted eagle rays (Aetobatus narinari) infested with monogean trematodes

Max Janse1* and Fred H.M. Borgsteede2

1Burgers’ Zoo, Schelmseweg 85, 6816 SH Arnhem, the Netherlands, 2Institute for Animal Science and Health (ID-Lelystad), P.O. Box 65, 8200 AB Lelystad, the Netherlands

Abstract Captive white-spotted eagle rays (Aetobatus narinari) were infested with Clemacotyle australis (Monogenea: Monocotylidae) on the skin and with a species of the Hexabothriinae on the gills. Different behavioural changes have been described caused by these infections. Oral treatment with 10-40 mg praziquantel per kg bodyweight had no effect. Bath treatment with 20 mg praziquantel per litre for 45-90 minutes showed good results against both parasite species. The presence of cleaner wrasse (Labroides dimidiates) in the display tank decreased the infections of the rays.

Introduction Materials and Methods Trematodes belonging to the Monogenea have Origin and maintenance of the rays been described from many elasmobranchs in Eight white-spotted eagle rays, originally captivity. A good overview is given by from the Maldives, were kept at the quaran- Cheung (1993). Infected fish may die if they tine facilities of Burgers’ Ocean, Arnhem, the remain untreated. Treatment with Netherlands. The rays were kept in three praziquantel has been proven to be effective round black tanks (diameter ca. 3 m, water against monogenean infections (Schmahl and height ca. 1 m). Water temperature was be- Mehlhorn, 1985; Schmahl and Taraschewski, tween 25° and 26°C, pH between 7.9 and 8.1,

1987; Schmahl et al., 1989). salinity between 33 and 34 ppt and O2-con- centration between 95 and 98%. Body width White-spotted eagle rays (Aetobatus narinari) of the rays was between 37 and 56 cm, their kept at Burgers’ Zoo in Arnhem, the Nether- estimated body weight between 0.5 and 4.0 lands showed behavioural changes and kg. After 2 to 4 months in quarantaine the rays proved to be infected with monogeneans. The were transfered to a display tank of 1.5 mil- aim of the present study was to describe the lion litre. Water temperature was between different behaviour of the infected rays and 25.0° and 25.5°C, pH between 7.9 and 8.1, sa- to measure the effect of a praziquantel treat- linity between 33.0 and 33.5 ppt and nitrate ment. As an alternative method for chemo- - levels at 20-25 mg NO3 -N/l. therapy, cleaner wrasses (Labroides dimidiates) were introduced in the display tank with the rays. Bull. Eur. Ass. Fish Pathol., 23(4) 2003, 153

Feeding of the rays for 90 minutes (Noga, 2000; J. Coreira, pers. The first month after arrival, the rays were comm.). In the first trial, the bath (25°-26°C) daily fed three times a day, 7days a week, with was aerated with pure oxygen to be sure that mussel (Mytilus edulis), razor shell (Ensis the O2-content stayed above 80%. The results siliqua), gamba (Penaeus sp.), squid (Loligo sp), were not very promising, therefore, to avoid

Atlantic herring (Clupea harengus), whiting the possible influence of the pure O2, the trial (Merlangius merlangus), mackerel (Scomber was repeated with compressed air. scombrus), scad (Trachurus trachurus) and Treatment in the display tank ansjovis (Engraulis encrasicolus). In the second When fish are kept in a display tank it is diffi- month of quarantine the rays were trained to cult and stressful for the fish to take them out. feed individually from a stick. After 2 months, Bath treatment is under those conditions no the rays were fed twice a day for six days per option and therefore it was investigated if the week with the same food items as in the first presence of cleaner wrasses (Labroides month. These items were alternatively offered dimidiatus) would be of influence on the ex- to encourage a variable diet and to avoid food ternal appearance and behaviour of the rays. preference.

Treatment Results and Discussion Due to behavioural changes and the subse- Behavioural changes quent demonstration of monogeneans on the Within a couple of days after arrival, some of skin, it was decided to treat the rays with the rays showed a stressful behaviour that be- praziquantel. came worse within two weeks. This was ex- Oral treatment pressed by: The first oral treatment was given at a dose tips of the pectoral fins were kept high rate of 10 mg praziquantel per kg body weight above the median line during swimming; (kgBW). The drugs were offered as a part of a spinning movements where the body was tablet in the food items (in the tail of the held in a vertical position; gambas or under the skin of food fish). Possi- tail and pelvic fins were angled upwards ble regurgitation was carefully observed. The during swimming; effect of the treatment was measured on the jumping out of the water against the net basis of presence of monogeneans in skin coverage of the tank; scrapings of the dorsal side of the pectoral fins swimming against the current close to the taken before and after treatment . Because of water outlets; lack of results, the study was repeated with upside down swimming in one extreme an oral dose of 40 mg per kgBW. case; Bath treatment regular resting on the bottom; scratching with the ventral side on the Due to the lack of results with the oral treat- bottom of the tank. ment, bath treatment was given. We started with a dose of 20 mg praziquantel per litre Bull. Eur. Ass. Fish Pathol., 23(4) 2003, 154

Praziquantel dose Mode of No. No. consecutive Effect (mg/kg body weight) application treatments days treatment 1t0.0 T41able Non e 1t4.3 T21able Non e 1t6.7 T21able Non e 2d0.0 L11iqui Non e 2t5.0 T22able Non e 4t0.0 T11able Non e

Table 1. Oral treatment with praziquantel of 7 captive white-spotted eagle rays (Aetobatus narinari) infected with monogenetic trematodes

This behaviour caused haemorrhages on the Oral treatment tips and sides of the pectoral fins and on the The results of the oral treatment are presented skin under the pectoral girdle. Successful in Table 1. Skin scrapings after the treatment treatment was given by oral dosing of did not show a reduction in the parasite in- enrofloxacin (Baytril®, Bayer) at 10mg per festation. Possibly the treatment should have kgBW per day during 7 days. The haemor- been done over a longer period to get better rhages healed within a month. However, the results. skin became paler in colour. Skin scrapings Bath treatment showed that the colour change was due to a The results of the bath treatment are shown thick layer of mucus. Large numbers of mono- in Table 2. The treatment gave much better genetic trematodes identified as Clemacotyle results than the oral treatment. The treatment australis were present. One ray died 58 days accompanied with oxygenation with pure O after arrival due to the monogenean infection 2 gave some result, but less than with aeration. and total exhaustion. This parasite has been The treatment resulted in a normal behaviour earlier described by Beverley-Burton and of the rays. After treatment in combination Whittington (1995). with aeration, many parasites could be col- Treatment lected from the bottom of the tank. Identifi- Treatment of monogeneans in elasmobranchs cation showed that not only C. australis was is often done with trichlorphon (Gruber and present, but also a species belonging to the Keyes, 1981; Stoskopf, 1993). However, we subfamily Hexabothriidae. Because these had bad experiences with the treatment of a parasites were not found in the skin scrapings, cow nose ray (Rhinoptera bonasus) and a white- it is very probable that they parasitized the spotted eagle ray who died after bath treat- gills. ment with Trichlofon Tugon®80 (Bayer) at a All parasites on the bottom of the treatment dose of 0.2 mg per litre in a mixed tank were still alive and remained so for at elasmobranch display tank. Necropsy showed least four hours. The effect of treatment was in both animals large congestions in their go- that they lost contact with the host, maybe due nads. Therefore we decided to try oral and to temporary paralysis of the muscles in- bath treatments with praziquantel (Droncit®, Bayer). Bull. Eur. Ass. Fish Pathol., 23(4) 2003, 155

Conc. (mg Oxygenation Treatment Results (decrease in parasite no.) praziquantel/l) /aeration time Neone Seom Complet

2O0.0 100% 2 92200 1r9.3-20.5 A0i 9013 1r9.4-20.5 A5i 4011 2r5.0 A5i 4002 Table 2. Bath treatment with praziquantel of captive white-spotted eagle rays (Aetobatus narinari) infected with monogenetic trematodes. volved with their clamp mechanism. It is not was thought that part of the problem was clear if these “free living” parasites can clamp caused by small confined space of the quar- to their host again during a subsequent con- antine tank. This way two animals were re- tact. Maybe that a higher dose of praziquantel leased in the large display tank creating less would kill the parasites, but at the dose of 25 confinement stress. Within one week they had mg/l the rays became already disoriented and to be removed from the tank since feeding were breathing heavily, so that a higher dose became a problem. may be toxic for the rays as well. The disori- Eight cleaner wrasses (Labroides dimidiatus) entation may also be caused a pH drop (ap- were introduced to reduce the trematode in- proximately 0,3-0,5 pH decrease) of the wa- fection. It was observed that the cleaner ter during the treatment. wrasses regularly “cleaned” the skin of the Biological treatment in the display tank rays and gradually the skin colour lost its pale After the bath treatment, the 7 rays were kept greyish colour and became darker. Therefor for 20 months without problems in a multi- indicate that the cleaner wrasses were able to ple species display tank. Gradually some rays control the parasites on the skin. Only one ray developed pale greyish patches on the dorsal had to be removed from the display tank and side, identical to the colour change observed was treated in a bath after which he was re- in the quarantine period when infected by turned to the tank. skintrematodes. The rays were caught from Oral treatments with praziquantel proved to the display tank and a skin scrape was done. be ineffective against skin monogeneans On six rays, juvenile C. australis could be (Clemacotyle australis) of white-spotted eagle found and on two rays also adult worms. On rays (Aetobatus narinari). Bath treatment of 25 one ray no skinparasites were found. mg praziquantel for 45 minutes with aeration Possibly the effect of the bath treatment was proved to remove the parasites from the skin, not 100% and living parasites were brought although the parasites did not die as they were with the rays into the display tank. Also the found alive on the bottom of the tank. In big display tank may have become infested by the display tanks, cleaner wrasses (Labroides trematodes due to the introduction of two in- dimidiatus) seem to be able to control the para- fected rays one months after their arrival. It site infection at a level which is not harmful for the rays. Bull. Eur. Ass. Fish Pathol., 23(4) 2003, 156

Acknowledgements Noga, E.J. (2000) Fish Disease. Diagnosis and treatment. 367 pp. Iowa State University Without the help of all keepers of Press. Ames, USA. Burgers’Ocean the results would not have been so successful. We would also like to Schmahl, G. and Mehlhorn, H. (1985) Treat- thank Joao Coreira (Ocenanoria de Lisboa, ment of fish parasites. I. Praziquantel effec- tive against Monogenea (Dactylogyrus vastator, Portugal) and Danny Winkels (Waterweelde Dactylogyrus extensus, Diplozoon paradoxum). Wholesales, Den Haag, the Netherlands) for Z. Parasitenkunde. 71: 727-737. their suggestions about the treatments. Schmahl,G. and Taraschewski, H. (1987) Treat- ment of fish parasites. 2. Effects of References praziquantel, niclosamide, levamisole-HCl, Beverley-Burton, M. and Whittington, I.D. and metrifonate on Monogenea (Gyrodactylus (1995) Clematocotyle australis (Monogenea: aculeati, Diplozoon paradoxum). Parasitol. Res. Monocotylidae) from the white-spotted eagle 73: 341-351. ray Aetobatus narinari (Rajiformes: Schmahl, G., Taraschewski, H. and Mehlhorn, Myliobatididae) on the Great Barrier Reef: H. (1989) Chemotherapy of fish parasites. redescription, emended generic diagnosis, Parasitol Res. 75: 503-511. and oncomiracidium. J. Parasitol. 81: 616-625. Stoskopf, M.K. (1993) Shark pharmacology Cheung, P.J. (1993) Parasitic diseases of and toxicology. In: Fish Medicine (Stoskopf, elasmobranchs. In: Fish Medicine (Stoskopf, M.K., Ed.) Chapter 102, pp. 809-816. Saunders M.K., Ed.) Chapter 100, pp. 782-807. Saunders Company, Philadelphia. Company, Philadelphia.

Gruber, S.H. and Keyes, R.S. (1981) Keeping sharks for research. In: Aquarium systems. (Hawkins, A.D., Ed.) Chapter 14, pp. 373-402. Academic Press, London.