gamithromycin and Respiratory-Tract-Diseases

The objective of this study was to evaluate one strategy for control (metaphylaxis) of bovine respiratory disease, with and without co-morbidity with otitis media, in dairy heifers at a commercial development facility. Individual heifers were the experimental unit. At weaning, 1 of 3 experimental treatments (gamithromycin, tulathromycin, or no medication) was randomly assigned to 1,567 heifers from 11 different dairies. Gamithromycin was administered to 631 heifers, tulathromycin was administered to 621 heifers, and no medication was administered to 315 heifers (negative control). Heifers were then commingled and penned according to body weight. Each pen contained heifers from each group, and periodically, larger numbers of heifers were penned together. All heifers were observed for the subsequent 42 d and treated according to protocols prescribed for the facility. Morbidity due to respiratory disease was less for heifers medicated with gamithromycin than for heifers medicated with tulathromycin. Morbidity due to respiratory disease was less for heifers medicated with gamithromycin than for heifers in the negative control group. Fewer heifers medicated with either antimicrobial were subsequently treated because of co-morbidity with otitis media. Mortality was not different among the treatment groups. Heifers medicated with either antimicrobial had greater average daily gain than did heifers in the negative control group.

Topics: Animals; Anti-Bacterial Agents; Body Weight; Cattle; Cattle Diseases; Disaccharides; Female; Heterocyclic Compounds; Macrolides; Morbidity; Otitis Media; Random Allocation; Respiratory Tract Diseases; Weaning

OBJECTIVE To compare predictive values, extent of agreement, and gamithromycin susceptibility between bacterial culture results of nasopharyngeal swab (NPS) and bronchoalveolar lavage fluid (BALF) samples obtained from calves with bovine respiratory disease (BRD). ANIMALS 28 beef calves with clinical BRD. PROCEDURES Pooled bilateral NPS samples and BALF samples were obtained for bacterial culture from calves immediately before and at various times during the 5 days after gamithromycin (6 mg/kg, SC, once) administration. For each culture-positive sample, up to 12 Mannheimia haemolytica, 6 Pasteurella multocida, and 6 Histophilus somni colonies underwent gamithromycin susceptibility testing. Whole-genome sequencing was performed on all M haemolytica isolates. For paired NPS and BALF samples collected 5 days after gamithromycin administration, the positive and negative predictive values for culture results of NPS samples relative to those of BALF samples and the extent of agreement between the sampling methods were determined. RESULTS Positive and negative predictive values of NPS samples were 67% and 100% for M haemolytica, 75% and 100% for P multocida, and 100% and 96% for H somni. Extent of agreement between results for NPS and BALF samples was substantial for M haemolytica (κ, 0.71) and H somni (κ, 0.78) and almost perfect for P multocida (κ, 0.81). Gamithromycin susceptibility varied within the same sample and between paired NPS and BALF samples. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated culture results of NPS and BALF samples from calves with BRD should be interpreted cautiously considering disease prevalence within the population, sample collection relative to antimicrobial administration, and limitations of diagnostic testing methods.

Topics: Animals; Bronchoalveolar Lavage Fluid; Cattle; Cattle Diseases; Genome, Bacterial; Macrolides; Male; Mannheimia haemolytica; Nasopharynx; Pasteurella multocida; Pasteurellaceae; Predictive Value of Tests; Respiratory Tract Diseases