The Efficacy of Tulathromycin
Mar. 23, 2021
The objective of this negative controlled, blinded, randomised, parallel group study was to compare the efficacy of two injectable macrolide antimicrobials, tulathromycin and tildipirosin, administered by single subcutaneous injection at dose rates of 2.5 and 4.0 mg kg−1 bodyweight, respectively, in the treatment of an experimentally induced Mycoplasma bovis infection in calves. A total of 238 M. bovis‐negative calves were challenged on three consecutive days with M. bovis by endobronchial deposition.
Post‐challenge, a total of 126 animals fulfilled the inclusion criteria and were randomly allocated to three treatment groups: tulathromycin, tildipirosin and saline. Clinical observations for signs of respiratory disease and injection site assessments were conducted daily for 14 days post‐treatment. The animals were then killed, the lungs were examined for evidence of lesions, and samples collected for bacterial isolation. Calves treated with tulathromycin had a lower percentage of lung with lesions (P = 0.0079), lower mortality (P = 0.0477), fewer days with depressed demeanour (P = 0.0486) and higher body weight (P = 0.0112) than calves administered tildipirosin.
Mycoplasma bovis is one of the main primary and secondary bacterial pathogens associated with the bovine respiratory disease (BRD) complex along with Mannheimia haemolytica, Pasteurella multocida and Histophilus somni, and constitutes a major source of both welfare and financial concern for the cattle industry worldwide Manusell & Donovan 2009). It is an important cause of respiratory disease and arthritis in feedlot cattle and young dairy and veal calves worldwide as well as being a causative agent of mastitis in dairy cattle (Maunsell et al. 2011). In Europe, M. bovis is considered to be involved in BRD outbreaks in one to two‐thirds of herds (Nicholas & Ayling 2003; Vangeel et al. 2011), although in the past, the difficulties with culturing the organism in the laboratory may have resulted in an underestimate of the actual number of cases confirmed.
Like all Mollicutes, M. bovis is inherently refractory to certain groups of antimicrobials, such as beta‐lactams, because it does not possess a cell wall, which limits the range of effective products available for its control. Commercially available M. bovis bacterin vaccines have poor efficacy for the prevention of M. bovis‐associated respiratory disease in calves (Maunsell et al. 2009; Soehnlen et al. 2011) although work to develop more effective vaccines is ongoing (Zhang et al. 2014). As a result, treatment and prevention of the disease in the field is limited at present to management strategies and antimicrobials. Evidence is accumulating that the susceptibility of M. bovis to antimicrobials is reducing (Nicholas et al. 2000; Gautier‐Bouchardon et al. 2014), potentially further limiting the range of effective products available.
Tulathromycin injection is a 15‐membered semi‐synthetic macrolide antimicrobial. Due to the unique chemical structure of the molecule, which has three nitrogen/amine functional groups, tulathromycin is the first member of a novel subclass of macrolides known as triamilides (Evans 2005). Tulathromycin is authorised by the European Medicines Agency (EMA) for the treatment and prevention of BRD associated with Mannheimia haemolytica, Pasteurella multocida, Mycoplasma bovis and Histophilus somni. The efficacy of tulathromycin in the treatment and prevention of M. bovis infections in cattle has been established in several studies (Godinho et al. 2005; Moyaert et al. 2012). Tildipirosin (Zuprevo®, MSD Animal Health) is a semi‐synthetic derivative of the naturally occurring 16‐membered macrolide tylosin. Tildipirosin is authorised by the EMA for the treatment and prevention of BRD associated with Mannheimia haemolytica, Pasteurella multocida and Histophilus somni. The in vivo efficacy of tildipirosin for the treatment or prevention of M. bovis infections has not yet been reported.