Pulmonary lesions and clinical disease response to Mannheimia haemolytica challenge 10 days following administration of tildipirosin or tulathromycin.
This clinical trial evaluated the impact of metaphylactic antimicrobial administration 10 d before experimental inoculation with Mannheimia haemolytica (MH) to mitigate pulmonary lesions. Thirty-three crossbreed heifers were procured as a single group and were randomly allocated to 1 of 3 blocks and to treatment, tildipirosin (ZUP; 4 mg/kg) or tulathromycin (DRX; 2.5 mg/kg) or saline (SAL; 1 mL/45.5 kg), within block on arrival at Kansas State University. All trial procedures were staggered by 7-d intervals for each block, resulting in all animals within a block receiving treatment, challenge, and necropsy on the same dates. Heifers within each block received an endoscopic MH challenge 10 d following treatment administration (d 0) and were housed in individual indoor stalls for 3 d postchallenge. Clinical illness scores (CIS), respiration quality scores, appetite scores, and injection site reactions were recorded on all animals from d 0 through d 13. Rectal temperatures were measured once daily on all animals from d 8 through d 13. Heifers were necropsied, and lung lesions were evaluated on d 13. Lung lesion data were evaluated using nonparametric methods (Kruskall-Wallis), and standard least squares models were used to evaluate the remaining variables. The pulmonary lesion scores (percentage of affected lung) ranged from 3.3% to 39.8% for all heifers with 92% (11/12) of ZUP-treated heifers having <10% lesions. Tildipirosin-treated heifers had lower (P < 0.05) lung lesion scores when compared with DRX- and SAL-treated heifers. Lung weight expressed as a percentage of BW was lower (P < 0.05) in ZUP heifers compared to DRX- and SAL-treated heifers. The probability of receiving abnormal CIS, appetite scores, and respiratory scores was lower (P < 0.05) in ZUP-treated heifers compared to DRX- and SAL-treated animals. This study showed that heifers treated with tildipirosin 10 d before MH challenge have less pulmonary damage and fewer clinical signs of illness compared to heifers treated with DRX or SAL.
Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan 66506.
D E
DE
Amrine
B J
BJ
White
R L
RL
Larson
D A
DA
Mosier
D000818:Animals; D000890:Anti-Infective Agents / Q000627:therapeutic use*; D019072:Antibiotic Prophylaxis / Q000379:methods* / Q000662:veterinary; D002417:Cattle; D004187:Disaccharides / Q000627:therapeutic use*; D005260:Female; D006571:Heterocyclic Compounds / Q000627:therapeutic use*; D008168:Lung / Q000187:drug effects* / Q000473:pathology; D016978:Mannheimia haemolytica / Q000276:immunology*; D012766:Pasteurellosis, Pneumonic / Q000188:drug therapy* / Q000276:immunology / Q000382:microbiology; D015645:Tylosin / Q000031:analogs & derivatives* / Q000627:therapeutic use; D018942:Macrolides
D000890:Anti-Infective Agents; D004187:Disaccharides; D006571:Heterocyclic Compounds; D015645:Tylosin; C576258:20,23-dipiperidinyl-mycaminosyl-tylonolide; C485204:tulathromycin; D018942:Macrolides