Captive African elephants (Loxodonta africana) are susceptible to many types of gram negative bacterial infections such as Escherichia coli, Mycoplasma spp., Salmonella spp., Klebsiella spp., Pseudomonas spp., and Proteus spp. Enrofloxacin (Baytril®, Bayer Health Care, Animal Health Division, Shawnee Mission, KS) is a potentially effective antibiotic for treatment of these bacterial infections in elephants. Very limited data exists on the pharmacokinetics of enrofloxacin in elephants2 and most of the dosage regimes for gastrointestinal absorption are based on horse dosages since they share a similar gastrointestinal tract1.
Three African elephants from Wildlife Safari in Winston, Oregon (two 37-year-old females and one 26-year-old male) were used to determine whether therapeutic levels of enrofloxacin could be achieved through rectal administration of liquid injectable enrofloxacin (Baytril 100®, 100 mg/ml; Bayer Health Care, Animal Health Division, Shawnee Mission, KS) at a dosage of 2.5 mg/kg. A pretreatment baseline blood sample was collected. Following administration, blood samples were collected at 45 minutes, 1.5, 2.5, 5, 9, 23, and 36 hours to determine plasma enrofloxacin levels. Plasma enrofloxacin levels were measured at North Carolina State University, College of Veterinary Medicine using high-performance liquid chromatography (HPLC) analysis. Plasma ciprofloxacin levels were measured concurrently.
Results indicate plasma concentrations of enrofloxacin did not reach adequate bactericidal levels for any of the following common bacterial isolates in captive elephants: Mycoplasma spp., Escherichia coli, Salmonella spp., Klebsiella spp., Pseudomonas spp., and Proteus spp. The study determined that a rectally administered dosage of 2.5 mg/kg of liquid injectable enrofloxacin was insufficient to obtain therapeutic levels in African elephants. The low plasma levels of enrofloxacin in all three elephants may be a result of poor absorption in the distal large intestine. A future study will determine if oral administration provides a more efficient mode of drug delivery and absorption in African elephants. It is also possible that the current dosage of 2.5 mg/kg is too low to achieve adequate therapeutic levels.
I would like to thank the elephant and veterinary staff at Wildlife Safari for their participation in conducting this study. Thanks to Doctors Modesto McClean, Jason Bennett, Andi Chariffe, Tessa Lohe, and Benji Alacantar. Also, thanks to Dinah Wilson, Carol Matthews, Anthony Karels, Mary Iida, Shawn Finnell, Patches Stroud, and Katie Alayan.
1. Haines GR, et al. Serum concentrations and pharmacokinetics of enrofloxacin after intravenous and intragastric administration to mares. Can J Vet Res. 2000;64(3):171–177.
2. Sanchez CR, et al. Pharmacokinetics of a single dose of enrofloxacin administered orally to captive Asian elephants (Elephas maximus). Am J Vet Res. 2005;66:1948–1953.