The effect of reduced treatment time and dosage of enrofloxacin on the course of respiratory disease caused by avian metapneumovirus and Ornithobacterium rhinotracheale.

A dose titration and reduced duration medication study were performed to evaluate the current enrofloxacin treatment schedule in growing turkeys experimentally infected with avian metapneumovirus and Ornithobacterium rhinotracheale. Experimental groups of 17 four-week-old turkeys were first infected with avian metapneumovirus and 3 d later with O. rhinotracheale. Enrofloxacin treatment in the drinking water was started 24 h after O. rhinotracheale inoculation. In the dose titration study, enrofloxacin doses of 5, 10, and 20 mg/kg of BW were administered for 5 successive days. In the reduced duration medication study, the following enrofloxacin regimens were compared: 25 mg/kg of BW per day on d 0 and 2; 15 mg/kg of BW per day on d 0, 2, and 4; and 10 mg/kg of BW for 5 successive days. In both studies, all enrofloxacin treatments were equally efficacious (i.e., equally capable of shortening the course of clinical disease), eliminating O. rhinotracheale from the respiratory tract and reducing gross lesions. Ornithobacterium rhinotracheale bacteria were not recovered from any of the birds on enrofloxacin-supplemented media, indicating that none of the used treatment regimens promoted the selection of bacterial clones with reduced susceptibility or resistance to this antimicrobial agent. In conclusion, none of the alternative enrofloxacin treatment regimens yielded better results than the current prescribed treatment (i.e., 10 mg/kg of BW for 5 successive days) of O. rhinotracheale infections in turkeys. However, the reduced duration of application would offer a less time-consuming and equally effective alternative.