Disinfecting For Strangles

Q. I have a pony on a farm where strangles has broken out. There are about 80 horses on this farm on about 100 acres (split into different pastures). We don't know where the infection started, but horses which show signs are being treated. What do you do about a farm that is so big with so many horses? How do you treat that big of a problem? Can you spray the pastures with a bleaching agent? I am at a loss for what to tell the owner of this farm to do.  


A. Strangles is caused by a tough, gram-positive bacteria called Streptococcus equi. I hope the owner of this farm is working with a veterinarian, as indiscriminate use of antibiotics can cause the disease to linger in horses for extended periods of time.

The single best thing to do is not move any healthy-appearing horses around, since you don't know which horses are incubating the disease. If possible, the sick horses should be strictly isolated because they need more intensive care, and any nasal discharge or abscess material is highly contagious to other horses. Other factors that spread it are human hands, towels, grooming equipment, flies, and anything else that touches the discharges from a sick horse, then lands on a healthy horse's nose.

Horses which have been in contact with sick horses (from the same pasture or barn) should have their temperatures taken twice a day, since a rise in body temperature of 1.5°F over normal is an indicator that the horse might develop the disease. Horses with fever should be immediately isolated.

There is no disinfectant that can be safely used on pastures. Water and feed buckets should be daily cleaned with a detergent and disinfected with a phenolic disinfectant, then thoroughly rinsed prior to use.

The bacteria can persist in the environment for a variable amount of time, especially when protected by discharge material. Contaminated bedding should be disposed of properly and not spread on pastures, since it also can be a source of contamination.

The farm owner needs to work closely with a veterinarian since there is no easy solution to this tough problem.

About the Author

Roberta Dwyer, DVM, MS, Dipl. ACVPM

Roberta Dwyer, DVM, MS, Dipl. ACVPM, is a professor within the University of Kentucky's Maxwell H. Gluck Equine Research Center and editor of Equine Disease Quarterly.

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