Anyone who has dealt with a strangles outbreak knows the importance of biosecurity—including cleaning items of tack—in curbing the spread of the disease. While routine cleaning kills the causal bacteria on most surfaces, a new study from Sweden shows that extra effort is required to sanitize halters and other gear made of polyester webbing.

How strangles spreads

Strangles is the common name for a systemic infection caused by Streptococcus equi spp. equi bacteria. Affected horses can show a variety of clinical signs, including fever, nasal discharge and swollen or abscessed lymph nodes under the jaw. Infected horses may also show no clinical signs, but still harbor and spread the bacteria for weeks. Quarantine of new horses and disinfection of surfaces can reduce the risk of outbreak or contain one that has already begun.

To investigate the efficacy of various cleaning techniques in eliminating bacteria, researchers at the Swedish University of Agricultural Sciences inoculated wood, concrete, plastic, leather halters, leather gloves and polyester webbing halters with S. equi, and three days later testing confirmed the presence of the bacteria on the items. Three days after that, the items were cleaned using various techniques. Two days later, the items were re-tested for S. equi.

Where bacteria survived longest

The researchers found that the bacteria were most likely to survive on nylon halters, persisting even when the items were washed in conventionally hot (104 degree F) water and tumble dried on the highest temperature setting (158 degrees F) for an hour. After this process, 14 of the 16 halters still tested positive for S. equi. However, when the nylon halters were washed in a machine with scalding hot water (140 degrees F) and dried in the laundry, no bacteria remained.

The researchers say the rough texture of webbing  likely helps bacteria survive routine cleanings. “I think  all material where the dirt  can ‘hide’ is a challenge,”  says  Anneli Rydén, PhD.  “The dirt must be removed. The bacteria can hide in  the dirt, and the dirt can hide in specific materials with a rough surface.”

In contrast, the researchers discovered that leather halters did not readily support the survival of S. equi. In fact,  even without any cleaning some inoculated leather items tested negative for the bacteria days later. While it’s not clear why leather didn’t seem to harbor S. equi, the researchers say this appears to be a universal characteristic of the material.

Leather and other materials

“We thought it could be the way [leather is] tanned,” says Rydén. “However, the surface is smooth compared with the nylon halters. And both were very old (at least 20 years) halters. But also newly manufactured leather material did not support the bacteria.”

The other surfaces—wood, concrete and plastic—were successfully disinfected using routine cleaning techniques.

Rydén says that putting nylon halters in a wash cycle with extremely hot  water is the best method for disinfection, even when strangles isn’t an immediate concern. “I hope owners are using this method. However in other similar materials, like jackets and gloves, the recommendation from the manufacturers is often 40°C (104 degrees F), which might be too low.”   

Reference: “Effectiveness of cleaning and sanitation of stable environment and riding equipment following contamination with Streptococcus equi Subsp. equi,” Journal of Equine Veterinary Science, February 2023.