ORAL-ADMINISTRATION OF TYLOSIN PHOSPHATE FOR TREATMENT AND PREVENTIONOF PROLIFERATIVE ENTEROPATHY IN PIGS

Objective-To evaluate the efficacy of orally administered tylosin phos phate for prevention and treatment proliferative enteropathy (PE) in p igs. Animals-Crossbred pigs weaned at 24 days of age. Procedure-Pigs w ere challenge exposed with an inoculum of Lawsonia intracellularis str ain LR189/5/83. Seven control pigs received buffer solution. Of 33 of challenge-exposed pigs, 8 were untreated. Two groups of challenge-expo sed pigs were dosed orally with tylosin phosphate via a 2% stabilized premix, starting with 100 or 40 ppm 4 days before challenge exposure a nd continuing for 16 days, when the dose was reduced to 40 or 20 ppm, respectively, which was continued for 12 more days, Another group of c hallenge-exposed pigs was dosed orally with 100 ppm of tylosin phospha te commencing 7 days after challenge exposure and continuing for 21 da ys. Pigs were euthanatized and necropsied 4 weeks after challenge expo sure. Results-The 8 untreated pigs had reduced weight gain; 3 of them had moderate diarrhea 8 weeks after challenge exposure, Five pigs had gross lesions of PE at necropsy. Seven pigs had histologic lesions of PE with numerous L intracellularis organisms. None of the pigs in the control, nonchallenge-exposed, or the 3 groups given tylosin phosphate before or after challenge exposure had clinical signs or lesions of P E. Conclusion and Clinical Implications-Tylosin phosphate can be effec tive for prevention and for treatment of PE, using reported dosing sch edules. We can experimentally induce PE, using the pure culture challe nge-exposure model, for use in testing of treatments.