Experimental evaluation of tulathromycin as a treatment for Campylobacter jejuni abortion in pregnant ewes.

OBJECTIVE: To evaluate the efficacy of tulathromycin for prevention of abortion in pregnant ewes when administered within 24 hours after experimental inoculation with Campylobacter jejuni.

ANIMALS: 20 pregnant ewes between 72 and 92 days of gestation.

PROCEDURES: All ewes were inoculated with a field strain of C jejuni (8.5 × 108 to 10.6 × 108 CFUs, IV). Eighteen hours later, ewes received either tulathromycin (1.1 mL/45 kg [2.4 mg/kg], SC; n = 10) or sterile saline (0.9% NaCl) solution (1.1 mL/45 kg, SC; sham; 10). Ewes were euthanized immediately after observation of vaginal bleeding, abortion, or completion of a 21-day observation period. Necropsy was performed on all ewes, and tissue specimens were obtained for bacterial culture and histologic examination.

RESULTS: 1 sham-treated ewe and 1 tulathromycin-treated ewe developed signs of severe endotoxemia and were euthanized within 24 hours after C jejuni inoculation. Seven sham-treated and 2 tulathromycin-treated ewes developed vaginal bleeding or aborted and were euthanized between 4 and 21 days after C jejuni inoculation. The proportion of tulathromycin-treated ewes that developed vaginal bleeding or aborted during the 21 days after C jejuni inoculation (2/9) was significantly less than that for the sham-treated ewes (7/9).

CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that administration of tulathromycin to pregnant ewes following exposure to C jejuni was effective in decreasing the number of C jejuni -induced abortions. Because of concerns regarding the development of macrolide resistance among Campylobacter strains, prophylactic use of tulathromycin in sheep is not recommended.