Q: Can infectious diseases be passed from horse to horse by sharing bridles? I recently lent a friend a bridle when she forgot hers at an event, and someone else told us we should never do that because diseases can be passed on bits. Is that something we need to worry about? If so, would rinsing the bit off be enough to clean it, or should it be disinfected more thoroughly?

A: Several important pathogens associated with diseases of the skin, eyes, respiratory tract or mouth (gums, saliva) can be transmitted by switching a bridle or bit between horses. The most significant of these include the highly contagious equine influenza virus (flu), equine herpesvirus -1 and -4, equine arteritis virus and vesicular stomatitis virus, as well as strangles (Streptococcus equi spp equi) and ringworm (Trichophyton equinum).

Cleaning and disinfection of the bridle and bit will reduce the amount of pathogen present, but the level of disinfection depends on the surface, intensity of cleaning (that is, the removal of organic material), the use of a detergent and type of disinfectant. In other words, if a smooth metal bit has been thoroughly cleaned with soapy detergent and water and then rinsed, the chances for disease transmission are low, compared to a leather or fabric bridle that undergoes similar cleaning. 

Many disinfectants claim to “kill 99.9% of bacteria and viruses.” For these products to be effective, however, any material like hair, skin debris, fluids/mucus from eyes, nose and mouth must be removed first before application of the disinfectant. Furthermore, to be 99.9% effective, these disinfectants might be damaging to the bridle or bit. 

In summary, when travelling with your horse, avoid sharing tack or grooming equipment. And if borrowed gear is returned used but not cleaned, don’t use it on your own horse until it has been cleaned and disinfected properly.  

Lutz S. Goehring, DVM, MS, PhD
Gluck Equine Research Center 
University of Kentucky 
Lexington, Kentucky