Strangles is the common name for the contagious strep throat of all equines, no other animals get it, and is a very serious and very contagious bacterial disease caused by the bacterium Streptococcus Equi, variety: Equi. It can be passed from horse to horse the same way we pass our own strep throats around and that includes direct contact with the snotty nose, coughing near another horse, contaminated feed bins and waterers, and, of course, being carried around by humans to another horse or another location. This should tip you off to the problem of you and your horses trying to avoid being exposed to the bacterial exudates that you might not even be able to see. The only reasonably sure way of keeping your horses from getting sick is to vaccinate them long before they are exposed to the disease. There are several vaccines available through your veterinarian, including 2 injectables and one live culture squirted up the horses nose. The injectables are killed vaccines and are safe but usually cause stiff and sore muscles and sometimes even fevers for several days after injection. For those reasons, many vets will use the live intranasal vaccine, and even though it is alive, it causes much less reaction from the horse. It is harder to give correctly so should be done by an experienced professional and care should be taken not to contaminate any other sterile vaccines or injections done at the same time, as it can cause an infection in the muscle if injected with other sterile substances. For that reason, many vets will give it all by itself and not at the same time as other vaccines.
Be sure to check with your veterinarian about 'Strangles' vaccines and get the vets opinion about the different types and your need to vaccinate yearly and keep the animals safe from a very serious disease. Bob Saunders dvm