Marley, S.E., S.E. Knapp, M.C. Rognlie, J.R. Thompson, T.M. Stoppa, S.M. Button, S. Wetzlich, T. Arndt, and A. Craigmill. 1995. Efficacy of ivermectin pour-on against Ostertagia ostertagi infection and residues in the American bison, Bison bison. Journal of Wildlife Diseases. 31(1): 62-65.
ABSTRACT: Sixteen American bison, Bison bison, were artificially infected with 10^5 infective stage larvae of Ostertagia ostertagi on 21 April 1993. At 42 days post-infection eight bison were treated with 0.5% ivermectin pour-on (500 ug/kg bodyweight) and eight treated with the carrier only. Bison were necropsied 17 and 18 days post-treatment (21 and 22 June 1993, respectively). Mean (+/-SE) of 5,413 (+/- 1,716) adults and 565 (+/- 305) immature O. ostertagi were recovered at necropsy from bison treated with the carrier. No O. ostertagi were detected in bison treated with ivermectin pour-on. Based on the levels of the ivermectin marker metabolite in liver and adipose tissue 18 days post-treatment, the established bovine withdrawal time of 48 days appears adequate to insure that violative residues do not occur.
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Target Animal Safety and Tissue Residue Studies.
In cooperation with the NRSP-7, the safety (toxicity) and tissue residue studies for ivermectin pour-on will be completed this year. The goal of the efficacy and these studies is to obtain label clearance for use of ivermectin pour-on against Ostertagia ostertagi in American bison. Currently, no approved anthelmintics are available for treating bison.
The current safety and tissue residue studies run concurrently, and will begin in February with a March completion. Twenty-six head of yearling bulls will be held at the Center for Bison Studies and treated with ivermectin pour-on. The animals are then regularly examined for adverse reactions to the drug, and tissues are sampled from bison necropsied 1, 3, 5, and 7 days post-treatment to determine the accurate withdrawl period and ivermectin tissue residues.
Principal Investigator: Dr. Stuart E. Knapp
Some information on the NRSP-7 (formerly IR-4) can be found
on the
Current USDA Research Database at the
Community of Science Database Service.
Search for the Project Numbers MICL08052, MICL07581, MICL07604,
and MICL07577 when using the database search to find the reports
describing the NRSP-7. Also, search with the keyword "Bison" to find
other U.S. and Canadian research sposored by the USDA.
