Efficacy of fenbendazole against gastrointesti- nal nematodes in white-tailed deer

We provided fenbendazole to captive (N q 77) and free-ranging (3 study areas) white-tailed deer (Odocoileus virginianus) in Louisiana to determine effects on gastrointestinal nematode burdens. Fenbendazole reduced gastrointestinal nematode burdens of captive and free-ranging white-tailed deer. Mean eggs per gram of feces from captive deer decreased P<O.Ol and P<O.Ol, respectively) 89% and 84% after provision of fenbendazole in doses approximating 0.47 and 0.62 g/deer, respectively. Doses approximating 0.42-0.46 g/deer did not affect (P = 0.61) eggs per gram of feces collected from free-ranging deer. Mean eggs per gram of feces collected from free-ranging deer was affected by fenbendazole treatment (P= 0.04) and decreased an average of 86% (SE = 1.9) on the 3 study areas after provision of fenbendazole in doses approximating 1.67-1.82 g/deer. Eggs per gram of feces collected from the distal colon and abomasal parasite counts from abomasa of freeranging deer harvested on the study areas were associated positively (r = 0.706, P<O.OOl), were affected by fenbendazole treatment (P<O.Ol andP<O.Ol, respectively), and decreased 66% (SE = 5.1) and 52% (SE = 7.4), respectively, after provision of fenbendaFunding was provided by Hoeschst-Roussell Agri-Vet Company, Inc., Somerville, N.J. Additional materials were provided by Urbana Laboratories, St. Joseph, MO. Authors wish to thank T. Jones and G. Berger for use of their lands and V. Herbert and N. Bradley for assistance with data collections. This manuscript was approved for publication by the Director, Louisiana Agricultural Experiment Station as Manuscript 91-22-5248. Manuscript accepted 24 Oct. 1992. zole in doses approximating 1.67-1.82 g/deer. A reduction in the crosstransmission of gastrointestinal parasites common to deer and livestock might be possible through fenbendazole treatment of deer.