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~D61 Warc\ North American Journal of Aquaculture 69:207-210, 2007 @ Copyright by the American Fisheries Society 2007 DOl: 10. 1 577/A06-054. 1 1'70 ro [Communication] Removal and Quantification of Asian Tapeworm from Bony tail Chub Using Praziquantel DAVID L. WARD* Arizona Game and Fish Department, Research Branch, 2221 West Greenway Road, Phoenix, Arizona 85023, USA Abstract.- The spread of the Asian tapeworm Bothrio- cephalus acheilognathi has been identified as a potential threat to endangered cyprinid fishes, such as bony tail Gila elegans and humpback chub G. cypha. Praziquantel is often used to remove Asian tapeworms from these species, but little information is available on the effectiveness or side effects of these treatments. I performed laboratory experiments using bony tails (110--457 mm total length) to evaluate the dosage and time needed to effectively remove 100% of Asian tapeworms using praziquantel. A low dose of 0.7 mg/L for 24 h was not effective at removing all Asian tapeworms, whereas a 24-h exposure at 1.5 mglL and higher was 100% effective. A bath treatment of 12-h duration only appears effective at the highest dose of 36 mg/L, but not all Asian tapeworms are cleared from the host within this time frame. No short-term mortality or side effects of praziquantel treatment were observed. Praziquantel bath treatments can effectively and safely remove 100% of Asian tapeworms from bony tail if dosage and treatment duration are adequate. In some cases, repeated treatments may be necessary to ensure that Asian tapeworms are not spread into new environments. Endangered cyprinid fishes are increasingly being cultured or reared at fish hatcheries for reintroduction or translocation into areas where populations have become depleted. Rare species present challenges to fish culturists because they often need to be treated to remove parasites, such as the Asian tapeworm Bothriocephalus acheilognathi, but there is little information available on methods for treatment, treatment effectiveness, or potential side effects of treatment in these species. Asian tapeworms were probably introduced into North America with grass carp Ctenopharyngodon idella imported from China to control aquatic vegeta- tion (Hoffman and Schubert 1984) and have since become widespread through the stocking of infected fish and bait bucket introductions. Asian tapeworms are potentially fatal to multiple age-classes of fish (Schaperclaus 1986) and can cause high mortality when infecting new host species (Hoffman and Schubert 1984). Asian tapeworm is considered one of * E-mail: dwardagf@qwest.net Received July 27. 2006; accepted October 28. 2006 Published online June 11, 2007 the most dangerous cestodes of cultured carps (family Cyprinidae) in Europe, causing heavy infections in juvenile cyprinids, especially when spreading into new locations (Heckmann and Deacon 1987). When parasites are numerous, marked enlargement of the abdomen can occur with severe hemorrhagic enteritis and intestinal blockage (Hoole and Nisan 1994). Asian tapeworms can also weaken and eventually rupture the intestinal wall, causing damage to other internal organs (Heckmann 2000). The rapid life cycle and nonhost specificity of this parasite allows it to spread very quickly, making it difficult to control. Praziquantel (Droncit) is an anthelmintic developed by Bayer Corporation (Leverkusen, Germany) for treatment of tapeworm infestation ip humans and animals (Andrews et al. 1983). Praziquantel is absorbed by tapeworms directly from the treatment water and affects the parasite by breaking down the tegument, causing the cestode to undergo spastic paralysis and detach from the intestine of the host. The host then sheds the dead tapeworms as either whole worms or worm segments. An advantage of using praziquantel to evaluate parasite loads is that it does not require killing and dissecting fish. Praziquantel has been used effectively to treat parasites in many fish species (Poole et al. 1984; Schmahi and Taraschewski 1987; Sanmartin Duran et al. 1989; Plumb and Rogers 1990; Mitchell 1995) and has become the treatment of choice for control of Asian tapeworm in hatcheries and ornamen- tal fish ponds. Treatments typically consist of holding fish in a water bath that has been dosed with praziquantel for 12-24 h (Mitchell 2004). No stan- dardized methods for praziquantel use currently exist and little information is available on dosage effective- ness or side effects in endangered fishes. I conducted laboratory experiments using bony tail Gila elegans to evaluate the dosage and time needed to safely and effectively remove 100% of Asian tapeworms using praziquantel. Methods Red shiners Cyprinella lutrensis infected with Asian tapeworms were collected from the confluence of the Verde and Salt rivers in Arizona and transported to the 207