Bt Crystal Proteins for Control of Gastrointestinal Parasites in Livestock

As with ruminant livestock, anthelmintic resistance is a serious problem in the equine industry. Resistance has been reported to all drug classes labeled for equine usage, and prevalences are rapidly increasing. Multidrug resistant parasites are now a common finding on managed horse farms all over the world, which is posing an increasing threat to equine health and economy in the equine industry. The pharmaceutical industry has not introduced new anthelmintic drug classes for equine usage since the early 1980s, and there a no new developments expected in a foreseeable future. The University of Kentucky-based equine parasitologist, Dr. Martin Nielsen, will devote 10% of his fulltime effort to this study during the three study years. The work will include evaluating Bt crystal protein formulations in cecum-fistulated ponies and evaluating treatment efficacy of chosen formulations in studies planned for years 2 and 3. Our contribution to this study will include the following: 1) Establishment of three ponies with cecal fistulas. All procedures will be performed at the University of Kentucky Research Farm with assistance from an experienced equine surgeon. Once established, Bt crystal protein formulations will be evaluated, when evaluated orally versus directly in the cecum. Cecal content samples will be collected and shipped to the University of Massachusetts for analysis of Bt crystal protein content. Parasite fecal egg counts will be determined in the ponies to assess treatment efficacy. 2) Performance of controlled efficacy trials in ponies. In each of years 2 and 3, fifteen ponies naturally infected with cyathostomin parasites will be randomly allocated to three groups of five. Two groups will be treated with two different types of Bt crystal protein (year 2) and two different dosages of the same Bt crystal protein (year 3). The third group will be kept as an untreated control. Fourteen days post administration, all ponies will be euthanized and necropsied for generation of total worm counts for an evaluation of efficacy. Parasite specimens will be identified using morphological criteria.