• 1. Stanton AL, Kelton DF, LeBlanc SJ, et al. Effects of tulathromycin on incidence of various diseases and growth of young heifers. J Am Vet Med Assoc 2013; 243:267276.

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  • 2. Baytril 100 [package insert]. Bayer HealthCare LLC, Shawnee Mission, Kan.

  • 3. Extralabel animal drug use; fluoroquinolones and glycopeptides; order of prohibition. Fed Regist 1997; 62(99):2794427947. Codified at 21 CFR §530.41.

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  • 4.21 CFR §530.

Concerns about extralabel fluoroquinolone use in food-producing animals

Kurt Matushek DVM, MS, DACVS1
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  • 1 Editor-in-Chief.

In its July 15, 2013, issue, the JAVMA published a report1 on the effects of prophylactic tulathromycin administration on the incidence of various disease conditions in dairy heifer calves. The study was conducted at a commercial dairy heifer-raising facility in New York state, and calves included in the study were assigned to a treatment or control group at the time of arrival at the facility. Calves in the treatment group were given a single SC injection of tulathromycin (100 mg) at the time of arrival, and calves were observed for the next 8 weeks.

As described in the report, calves treated with tulathromycin were significantly less likely to develop droopy ears (considered indicative of otitis media), diarrhea, or a fever than were calves in the control group. However, incidences of bovine respiratory disease and lameness did not differ between groups.

Although the study focused on decreasing the incidence of various diseases, and not on the treatment of calves that developed any of those diseases, the authors did report that calves that developed droopy ears were given enrofloxacin, a fluoroquinolone antimicrobial, by barn staff at the time clinical signs were first observed.

Shortly after this report was published, the journal was contacted by a reader, who suggested that the described use of enrofloxacin in these calves appeared to be prohibited under current US FDA regulations. Enrofloxacin has been approved “for the treatment of bovine respiratory disease (BRD) associated with Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis in beef and non-lactating dairy cattle; and for the control of BRD in beef and non-lactating dairy cattle at high risk of developing BRD associated with M haemolytica, P multocida, H somni and M bovis.”2 Although otitis media (ear droop) can be caused by infection with M bovis, it is not a respiratory disease. Thus, use of enrofloxacin to treat droopy ears in dairy calves would not be in accordance with current label indications. And, the FDA has, since 1997, prohibited the extralabel use of fluoroquinolones such as enrofloxacin in food-producing animals.3

When contacted regarding these concerns, the authors pointed out that the use of enrofloxacin in these animals was not part of the experimental protocol, and that they did not prescribe the drug or promote its use. Further, prior to the start of the study, they had discussed with the farm owner which aspects of existing management and treatment protocols could be changed for the study, but found that the farm was unwilling to change existing treatment protocols.

We bring this issue to the attention of our readers not to call into question the conclusions of the study. The data appear sound, and because the outcome of interest was the proportion of calves that developed droopy ears, treatment of calves after clinical signs developed should not have had any effect on the authors’ findings.

However, the judicious use of antimicrobials in animals in general and in food-producing animals in particular is of paramount importance to the veterinary profession. Although debate continues as to the extent to which antimicrobial use in animals contributes to increases in antimicrobial resistance in bacterial organisms of importance in human medicine, it is clear that antimicrobial use in animals is not without risks.

The AVMA has been and continues to be a strong advocate for judicious use of antimicrobials in animals, and the JAVMA supports these efforts. The editors routinely review all manuscripts to identify potential concerns prior to publication. This includes concerns related to extralabel drug use, but also includes concerns related to compounding, animal welfare, pain management, euthanasia methods, and a wide variety of other things. When such concerns are identified, the manuscript is modified or rejected, depending on the circumstances.

Unfortunately, concerns related to the use of enrofloxacin in the report by Stanton et al1 were not raised prior to publication, and the editors have gone back to review the history of this manuscript to identify areas where our processes can be modified and strengthened. At the same time, we call on veterinarians—not just those in food animal practice, but all veterinarians—to redouble their efforts with regard to the judicious use of antimicrobials. We also stress that while judicious use principles allow for extralabel drug use under certain circumstances, they require that any such use be in compliance with current regulations.4 Current regulations unambiguously prohibit the extralabel use of certain drugs and substances in food-producing animals, and enrofloxacin is among the drugs so prohibited.

Judicious antimicrobial use is critical to protecting animal health and welfare and promoting public health and food safety and is vital to retaining current uses of antimicrobials in veterinary medicine. Without it, we may someday find ourselves in the position of not having access to crucial drugs needed to treat our patients.

  • 1. Stanton AL, Kelton DF, LeBlanc SJ, et al. Effects of tulathromycin on incidence of various diseases and growth of young heifers. J Am Vet Med Assoc 2013; 243:267276.

    • Search Google Scholar
    • Export Citation
  • 2. Baytril 100 [package insert]. Bayer HealthCare LLC, Shawnee Mission, Kan.

  • 3. Extralabel animal drug use; fluoroquinolones and glycopeptides; order of prohibition. Fed Regist 1997; 62(99):2794427947. Codified at 21 CFR §530.41.

    • Search Google Scholar
    • Export Citation
  • 4.21 CFR §530.