Streptococcus equi Survivability with Cleaning and Sanitation

A study examined the survivability of S. equi bacteria on different surfaces following various cleaning and sanitation procedures.
Leather halter hanging on stall door. Leather products do not support S. equi bacteria days after innoculation.
Leather halters did not support S. equi bacteria five days post-innoculation, but polyester-webbed halters still harbored bacteria when washed at lower temperatures. Getty Images

Streptococcus equi, the causative bacteria of strangles in horses, is highly transmissible not just from direct contact with infected horses but also from contaminated equipment and surfaces found in a stable environment. Previous studies have identified survival of S. equi for 34-72 days. The cooler the temperature, the longer the survival. Ambient temperatures in summer reduce survival of S. equi to 1-3 days. 

A study reviewed the efficacy of cleaning untreated wood, concrete tiles, plastic water buckets, new and unused leather halters, leather gloves and polyester webbed halters following inoculation of S. equi bacteria [Ryden, A.; Fernstrom, L.; Svonni, E.; Riihimaki, M. Effectiveness of cleaning and sanitation of stable environment and riding equipment following contamination with Streptococcus equi subsp. equi. Journal of Equine Veterinary Science(2022), doi:].

Three days after the materials were infected with S. equi, all were sampled for the bacteria and some pieces were cleaned and sanitized. Two days later, all treated and untreated materials were again evaluated for bacterial presence. Sanitation involved one minute of scrubbing in lukewarm water and alcohol ethoxylate detergent left to sit for 10 minutes, then rinsed with tap water. Two hours later, materials were soaked in disinfectant (potassium monopersulfate-maleic acid-sulfamic acid) and left to sit for two days. An extra number of 24 polyester-webbed halters were treated similarly and left for three days. Of these, 16 were washed for 39 minutes at 1040 F. Eight were dried by air; eight were tumble dried for an hour at 158F. The final eight polyester-webbed halters were washed at 1400 F for 43 minutes and air-dried for two days prior to bacterial sampling.

Leather materials (halters and gloves) did not support S. equi by five days post-inoculation even prior to cleaning and sanitation. It is possible that chemicals used in the tanning process have an effect on reducing bacterial survival.

Following cleaning and sanitation, all materials cultured negative except for 14 of 16 polyester-webbed halters that cultured positive (the lower wash temperature of 1040 F along with tumble drying did not effectively remove S. equi). However, the webbed halters washed at 1400 F cultured negative. 

The authors noted that the study was performed indoors at constant room temperature. Field conditions of variable temperatures might have additional effects on S. equi survivability. They further purported that with regular cleaning and sanitation, it is possible to remove S. equi from rough surfaces such as concrete and unfinished wood with porous and rough surfaces. The persistence of S. equi in polyester-webbed halters might be due to ease of absorption of contaminants into the woven fabric along with the ability of the material to retain moisture. Only when washed at 1400 F were the halters rid of bacteria. Recognition of the need for more intensive hygienic and sanitation practices is important for controlling fomite-related S. equi infection.

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