Abstract

Fenbendazole is a commonly used anthelmintic in fish, although sensitivities have been reported in temperate benthic freshwater species.^2,4 To investigate associations of fenbendazole with morbidity or mortality in teleost fish, a retrospective study was performed using the clinical records at the National Aquarium, Baltimore. Fenbendazole (Panacur 10%, Intervet Inc., Millsboro, DE) was provided as a medicated gel food at doses of 250 or 1000 mg/100 g of food once daily for two days. The electronic clinical records database Tracks® was queried for the term "fenbendazole" or "Panacur," and records of teleost fish between January 1, 2005 and December 31, 2010 were identified. The query returned 454 records of fenbendazole use in individual or groups of teleost fish during this period. Morbidity or mortality within ten days of fenbendazole use was identified in 44 cases. Medical records from the 44 cases were evaluated in detail, and morbidity/mortality event association with fenbendazole administration was categorized as likely, unlikely, or unknown. There were 21 likely events, 16 unlikely events, and 7 unknown events. The most commonly observed adverse effects likely associated with drug administration were tachypnea, dyspnea, gill pallor, lethargy, erratic swimming, decreased appetite, and death. Most adverse effects were observed between 4 and 6 days of treatment. Adverse effects were noted in 16 species from 9 genera: madtoms (Noturus spp.), suckers (Catostomus commersoni, Hypentelium nigricans), darters (Etheostoma spp.), brook trout (Salvelinus fontinalis), pencilfish (Nannostomus spp.), and small Amazonian catfishes (Corydoras spp., Brochis splendens, and Dianema urostriatum). The majority of fish sensitive to fenbendazole at these doses were New World freshwater benthic species. Further research is needed to critically assess toxicity, such as pharmacokinetics, drug distribution analysis, and toxicity trials.^1,3

References

1.  Davis LE, Davis CA, Koritz GD, Bevill RF. Comparative studies of pharmacokinetics of fenbendazole in food-producing animals. Vet Hum Toxicol. 1988;30:9–11.

2.  Hadfield CA, Clayton LA. Fish quarantine: current practices in public zoos and aquaria. J Zoo Wildlife Med. 2011;42:641–650.

3.  Kitzman JV, Holley JH, Huber WG, et al. Pharmacokinetics and metabolism of fenbendazole in channel catfish. Vet Res Commun. 1990;14:217–226.

4.  Noga EJ. Fish Disease: Diagnosis and Treatment. 2nd ed. Ames, IA: Wiley-Blackwell; 2010:398.