The clinical and histopathologic effects of potentiated chlorhexidine in the upper respiratory tract of horses

Vet Surg. 2021 Aug;50(6):1209-1217. doi: 10.1111/vsu.13649. Epub 2021 May 11.


Objective: To describe the bactericidal and fungicidal properties of a 0.0005% chlorhexidine (CHD) solution potentiated with EDTA-Tris buffers (CHD-EDTA-Tris) and evaluate the safety of 0.0005% CHD-EDTA-Tris in the upper respiratory tract (URT) of normal horses.

Study design: Clinical, prospective study.

Animals: Eight healthy, skeletally mature horses.

Methods: In vitro-serial dilutions of CHD-EDTA-Tris and EDTA-Tris alone were evaluated for bactericidal and fungicidal activity against Aspergillus fumigatus, Escherichia coli, Staphylococcus aureus, Streptococcus equi subspecies ssp. equi, Streptococcus equi ssp. zooepidemicus, and Pseudomonas aeruginosa. In vivo-eight healthy horses were topically treated twice with 30 ml of 0.0005% CHD-EDTA-Tris. Mucosal samples from each location were evaluated for the presence of inflammation or pathologic lesions.

Results: Solutions containing CHD were superior in fungal and bacterial killing to those without. In vitro-a 0.005% CHD-EDTA-Tris was 100% effective against all bacterial and fungal species evaluated, while a 0.0005% CHD-EDTA-Tris was less efficacious against A. fumigatus and S. equi ssp. equi. In vivo-a 0.0005% CHD-EDTA-Tris did not cause any clinical, gross, or histologic abnormalities when topically applied to the equine URT.

Conclusions: A 0.0005% CHD-EDTA-Tris was highly effective for killing of common bacterial and fungal isolates in the equine upper respiratory tract. Short-term topical treatment of the equine URT with dilute CHD did not cause gross or histological inflammation in the tissue.

Clinical significance: A 0.0005% CHD solution with EDTA-Tris should be considered for treatment of clinically relevant inflammatory or infectious conditions or in the URT of the horse.

Publication types

  • Clinical Trial, Veterinary

MeSH terms

  • Animals
  • Chlorhexidine* / pharmacology
  • Horse Diseases* / drug therapy
  • Horses
  • Nose
  • Prospective Studies
  • Streptococcal Infections* / veterinary
  • Streptococcus equi*


  • Chlorhexidine