Field Efficacy Study of Gamithromycin for the Control of Bovine Respiratory Disease in Cattle at High Risk of Developing the Disease

Bovine respiratory disease (BRD) is one of the most economically significant sources of losses arising from poor performance and mortalities in cattle entering feedlots. Antibacterial treatments are administered to cattle in the feedlots therapeutically or prophylactically for control of pathogens associated with BRD. Gamithromycin is an azalide 15-membered semi-synthetic macrolide antibiotic that has been developed for the treatment and control of BRD. Two separate field studies were conducted at feedlots in Texas and Nebraska to evaluate the efficacy of a single treatment with gamithromycin administered subcutaneously at 6.0 mg/kg body weight for control of BRD in calves at high risk of developing BRD associated with Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis, the primary pathogens responsible for outbreaks of BRD. The proportion of treatment successes in the group treated with gamithromycin was significantly higher (P<0.05) at both sites than in the saline-treated control group. There were no deaths associated with BRD in either group at either site. A single treatment with gamithromycin at the time of entry at the feedlot provided rapid and prolonged therapeutic and preventive efficacy against the primary pathogens responsible for outbreaks of clinical BRD for at least 10 days after treatment in each study.