2015 ACVIM Forum Research Abstract Program

PRESUMPTIVE FENBENDAZOLE TOXICOSIS IN THREE HOLSTEIN CALVES. Emily Barrell, Rebecca Ruby, Belinda Thompson, Theresa Southard, Daryl Nydam, Gillian Perkins. Cornell University, Ithaca, NY, USA Fenbendazole (FBZ) is a widely used anthelmintic that interferes with microtubule formation and is considered safe in ruminants. Studies have evaluated a 39 dose (15 mg/kg, PO, q24h for 3 days) for treatment of Giardia-induced diarrhea without complications. Other benzimidazoles have been toxic in a variety of species, resulting in bone marrow hypoplasia and intestinal crypt epithelial necrosis. This abstract describes the clinical findings and necropsy examinations of three 2-monthold Holstein heifer calves with presumptive FBZ toxicosis. The calves had received two courses of greater than 39 the labeled dose of FBZ for 3 days, no FBZ for 3 days, then another 3 days of treatment for presumptive Giardia-induced diarrhea. Clinical signs included fever, tachycardia, dyspnea, profuse diarrhea, and recumbency. All three animals had a persistent and absolute neutropenia. Despite treatment, one calf was euthanized due to a poor response and one calf died. Histologic examination of liver, lung, and intestinal epithelial cells revealed hyperplasia, cell atypia, irregular mitotic figures, and/ or ring mitosis and abnormally clumped chromatin. The bone marrow was hypoplastic with an overall cellularity <5%. The feces were negative for Salmonella spp., bovine viral diarrhea virus, rotavirus, and parasites, and positive for bovine coronavirus. The third calf was treated on-farm and recovered over several weeks. Based on histopathology and history of multiple animals affected, a toxic etiology was suspected, with the only common exposure being repeated administration of high-dose FBZ. This suggests that judicious use of FBZ in calves is warranted. The purpose of this study was to use molecular techniques to determine if dairy heifers are colonized with the same coagulase negative staphylococci (CNS) species before calving that are causing CNS intramammary infections (IMI) at parturition. Holstein and Guernsey heifers at the University of Missouri Foremost Dairy were longitudinally enrolled in the study. Samples including pre-partum mammary quarter secretions and swabbing samples of the teats, muzzle, perineum, and inguinal region were collected at approximately 14 day from expected calving date. Swabbing samples were collected using gas-sterilized electrostatic dusters (Swiffers Ã’ ). At calving, mammary quarter foremilk samples were collected twice, at approximately 3-5 and 7-9 days post-partum, for bacterial culture and somatic cell counting.