Colloidal Iron to Disinfect a Horse Hoof

Addition of colloidal iron oxide material to hoof scrubs with chlorhexidine yielded the most effective bacterial count reduction.

horse hoof veterinarians examining
Addition of colloidal iron oxide material to hoof scrubs with chlorhexidine yielded the most effective bacterial count reduction. Getty Images

At times there is a need for effective hoof disinfection. There are a variety of products available for this purpose. Italian researchers with concerns over antimicrobial resistance looked at the use of colloidal materials as an alternative to eliminating microorganisms and parasites from the skin surface with less adverse effects on skin as occurs with some currently used antiseptics [Isola, M.; Piccinotti, C.; Magro, M.; et al. Colloidal Iron Oxide Formulation for Equine Hoof Disinfection. Animals 2021, 11, 766; https://doi.org/10.3390/ani11030766].

Initially, an in vitro study established the ability of a colloidal suspension of iron oxide, organic acids and detergents (Iron Animals or IA) to eliminate Staphylococcus aureus. Iron oxide colloids catalytically induce cell death through production of cytotoxic free radicals; trichloroacetic acid precipitates protein by sequestering water molecules bound to proteins. Sodium dodecyl sulfate is a denaturing detergent to disrupt membranes and denature proteins while lowering surface tension to allow permeation of medication into the hoof for greater contact with microorganisms.

The in vivo study compared 10% povidone iodine (PI) and 4% chlorhexidine (CHx) separately, then looked at the effect of concurrent use of Iron Animals (IA) with each of those two antiseptics.

Eleven horses from the same farm and management were used for the in vivo part of the study. Hooves were cleaned with a hoof pick and trimming of the sole and frog as necessary. Then, a firm, sterile brush was used to perform two consecutive 3-minute scrubs, with sterile saline rinse in between. The foot was then dried with sterile gauze and a 2 cm2 frog sample was removed. Then 10 ml of IA was applied and wrapped in place with the hoof sealed inside a plastic bag and the limb held off the ground for 15 minutes. Then, the dressing was removed, and a second frog sample acquired.

This procedure was done for each antiseptic choice—two scrubs with PI on the left hoof or CHx on the right hoof. Each scrub treatment was followed by application of 10 ml of IA on the excised frog area and sole.

To test for efficacy of IA used alone, a fragment of LF hoof sole served as control while the RF hoof sole had two consecutive scrubs with PI, was rinsed and dried, then sampled. A rear hoof was prepared similarly, but instead of PI scrubs, gauze soaked in 10 ml of IA was placed on the hoof sole for 15 minutes, then a sample removed with a sterile scalpel.

Each tissue sample underwent microbiological analyses within 24 hours with the samples stored in saline and at an appropriately cold temperature.

Looking at the results:

  • CHx lowered bacterial load by seven-fold compared to PI.
  • PI alone did not accomplish sufficient disinfection.
  • After application of IA, both PI- and CHx-treated hooves had a significant reduction in bacterial load: 27% improvement for PI + IA; 55% improvement for CHx + IA.
  • IA applied by itself “showed a significantly lower bacterial load and a superior antibacterial effect compared to the rear hoof sample treated with PI.”

In summary, addition of the colloidal iron oxide material to scrubs with chlorhexidine yielded the most effective bacterial count reduction. Following use of IA, bactericidal activity of both disinfectants resulted in an overall improvement in 82% of all the cases.

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