SAFETY AND EFFICACY OF MILBEMYCIN OXIME AND LUFENURON TO TREAT SPP. INFESTATION IN SMOOTH BACK RIVER STINGRAYS () AND MAGDALENA RIVER STINGRAYS ().

Fish lice, ectoparasites of the genus , are branchurian crustaceans that can significantly impact fish health by causing mechanical damage to cutaneous barriers and increasing susceptibility to other infections. While many treatments have been reported in teleosts and invertebrates, there are no published treatments for elasmobranchs. This study evaluated the safety and efficacy of a commercial formulation of milbemycin oxime and lufenuron in freshwater stingrays for treatment of spp. Seven juvenile Magdalena river stingrays () and 10 juvenile smooth back river stingrays () had severe infestations of spp. that were identified visually and microscopically. Animals were treated with milbemycin oxime and lufenuron (at 0.015 mg/L and 0.30 mg/L, respectively) in a 6-hr immersion once weekly for two treatments. They were visually examined for skin lesions as well as behavior and appetite daily by animal care staff. A subset of animals was euthanized and necropsied on days 8, 9, 43, and 78 after treatment initiation. There were no spp. detected at the time of the second treatment. Complete gross and histologic evaluations were completed for all animals. At all time points, no gross abnormalities were detected with the exception of thin body condition in some animals; no spp. were noted. Histologic lesions were all attributed to poor nutritional state at the time of acquisition. No histologic evidence of acute or chronic toxicosis was detected. The commercial formulation of milbemycin oxime and lufenuron, applied at the dose and for the exposure time used in this study, effectively eradicated spp. in a population of juvenile and , and did not cause mortality or clinical gross or histologic evidence of acute or chronic toxicity.