EFFECTIVENESS OF 2 FLUOROQUINOLONES FOR THE TREATMENT OF CHRONIC RESPIRATORY-DISEASE OUTBREAK IN BROILERS

1. Chronic respiratory disease (CRD) caused by Mycoplasma synoviae in association with Escherichia coli is the disease most frequently encou ntered in poultry in Mexico. 2. Differences of antimycoplasmal activit y, pharmacokinetics and cost among fluoroquinolones were the impetus f or this clinical evaluation of efficacy of enrofloxacin and norfloxaci n-nicotinate in broilers with CRD. 3. A total of 99,600 broilers, natu rally infected with M. synoviae and E. coli, were treated with enroflo xacin (10 mg/kg/d for 3 d) (n = 49,800) or norfloxacin-nicotinate (20 mg/kg/d for 3 d) (n 49,800). 4. Based on survivor analysis, there were no significant differences of efficacy of the 2 drugs. Survivor proba bilities were above 0.99. 5. These results indicate that enrofloxacin and norfloxacin-nicotinate are efficacious for treatment of CRD. Quest ions remaining to be answered by other studies include: public health concern about the use of fluoroquinolones for the treatment of CRD; cl inical superiority of one of these drugs on the basis of an attribute other than antimicrobial activity, such as cost:benefit ratio or abili ty to prevent bacterial resistance. 6. Clinical efficacy is not a rele vant variable in assessing whether norfloxacin-nicotinate or enrofloxa cin should be used for the treatment of CRD associated with E. coli in broilers.