Study: Antibiotics Might Protect Horses during Transport

Long-distance transportation is a stressor for horses that could prompt poor performance, illness, and other life-threatening health issues. Recently, a team of Japanese researchers determined that certain antibiotic administration could reduce transport-related illness in our four-legged counterparts.

"During long-distance travel the horse's raised head induces inflammation, and the number of bacteria in the lower airways increases," explained Takeru Tsuchiya, DVM, from the Hidaka Training and Research Center at the Japanese Racing Association in Hokkaido. "Fevers that develop during or after transport caused by bacterial infections can cause respiratory pneumonia, which interrupt training and race schedules."

Previous studies found that administering interferon-α (an immune stimulant) before transportation correlated with decreased severity of transportation-associated fever and improved clinical condition after transportation.

"This protocol did not completely prevent fever in the horses, and further prophylactic measures are needed," added Tsuchiya.

Current data suggest that the antibiotic medication enrofloxacin (administered at 5 mg/kg of body weight) reaches the lungs following intravenous (IV) administration, and circulating levels remain elevated for 24 hours after administration. Tsuchiya and colleagues therefore hypothesized that enrofloxacin administration prior to travel could prevent fever associated with transportation.

To test this theory, the researchers randomly divided 32 Thoroughbreds being transported to a horse sale in Japan into two groups. They administered interferon-α (once daily for three consecutive days prior to shipping) to all study horses, but administered 5 mg/kg enrofloxacin IV on the day of transport to the treatment group only (the control group received saline).

Following a 26-hour van ride:

  • Three of 16 horses in the enrofloxacin group were febrile (rectal temperature greater than or equal to 38.5°C, or 101.3°F) versus nine of 16 control horses;
  • Two horses in the enrofloxacin group required additional antibacterial treatment (a penicillin-streptomycin combination) following transport compared to seven horses in the control group; and
  • No adverse effects to the interferon-α or enrofloxacin were noted in any horses.

"In addition to the decreased number of fevers, a beneficial impact of the enrofloxacin was noted on white blood cell counts and analysis of tracheobronchial aspirates (from the windpipe)," relayed Tsuchiya.

Considering the continued importance of judicious antimicrobial use to minimize the emergence of antimicrobial-resistant bacteria, the authors did emphasize that enrofloxacin should only be used as prophylaxis against transportation-associated fever when the duration of transportation is anticipated to be more than 20 hours.

Tsuchiya added, "It is also important to ensure that horses are not considered to be at risk for developing transportation-associated fever (e.g., if the horse has undergone laryngoplasty or has a history of pneumonia) before long-distance transportation."

The study, "Effects of a single dose of enrofloxacin on body temperature and tracheobronchial neutrophil count in healthy Thoroughbreds premedicated with interferon-α and undergoing long-distance transportation," appeared in July in the American Journal of Veterinary Research. The abstract can be viewed on Pubmed

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.