Strangles in Horses: Survival of Causative Bacterium on Equipment, Fixtures

The bacterium that causes strangles, Streptococcus equi subspecies equi, transmits easily from horse to horse and from horse to inanimate objects, such as tack, water buckets, and stall doors. Effectively cleaning equipment and fixtures decreases disease transmission, which is important in minimizing spread and recurrence.

According to a Swedish research team, S. equi is a hardy organism, surviving on wood for 63 days at 36° F (2° C), on glass and wood for 48 days at 68° F (20° C), and in the environment for 34 to 72 days.^*

“Exposure to sunlight and high temperatures decreases the bacterium’s survival to only a few days,” explained Catherine Whitehouse, M.S., of Kentucky Equine Research.

In addition to establishing appropriate biosecurity protocols, disinfection plays a key role in reducing disease transmission.

To evaluate the efficacy of one cleaning and sanitizing protocol, the researchers contaminated various items with S. equi, including concrete tiles, wooden boards, plastic water buckets, leather gloves, and halters made from leather and polyester webbing. The inoculated bacteria were then allowed to grow for three days. At that time, half of the inoculated surfaces were cleaned and sanitized. This protocol involved:

• Cleaning each surface/item for one minute with lukewarm water;
• Applying a detergent (alcohol ethyoxylate 15%) for 10 minutes;
• Rinsing off the detergent and leaving it to rest for 2 hours;
• Disinfecting with a combination of potassium monopersulfate, maleic acid, and sulfamic acid for two days.

Polyester halters underwent additional testing to evaluate the efficacy of this protocol. After letting 24 disinfected halters rest undisturbed for three days, 16 were washed in a washing machine at 104° F (40° C) for 39 minutes. The remaining eight halters were washed at 140° F (60° C) for 43 minutes. Halters were air-dried or tumble-dried.

Bacterial sampling of all surfaces that had been artificially contaminated with S. equi and then cleaned/decontaminated was performed three and five days later.

“After cleaning and sanitizing, all surfaces inoculated with S. equi were culture negative except for a subset of polyester halters,” said Whitehouse.

Fourteen of the 16 polyester halters washed at 104° F (40° C) and tumble-dried were still culture positive. But the polyester halters washed at 140° F (60° C) were culture negative.

In contrast, the researchers noted, “It appears that, even without cleaning and sanitation, leather products commonly used in horse sports fail to support longer-term survival of S. equi.”

Thus, except for the polyester halters, routine protocols for cleaning and sanitation are appropriate for eliminating S. equi from everyday items and barn surfaces.

“Effective cleaning and sanitizing protocols are imperative biosecurity measures for strangles given that this disease is highly infectious, easily causing outbreaks and economic losses,” concluded Whitehouse.

A robust immune system is essential for reducing disease severity, and a complete and balanced diet will allow the horse’s immune system to function optimally.

“For those horses that travel extensively or are exposed to outside horses, consider immune-boosting supplements such as vitamin E, vitamin C, and long-chain polyunsaturated fatty acids such as DHA and EPA found in EO-3,” advised Whitehouse.

 ^*Ryden, A., L-L. Fernström, E. Svonni, and M. Riihimäki. 2023. Effectiveness of cleaning and sanitation of stable environment and riding equipment following contamination with Streptococcus equi subsp. equi. Journal of Equine Veterinary Science 121:104204.