Epidemiology
Strangles is very contagious, especially with foals, spreading easily from horse to horse and often leading to large outbreaks with many horses affected. It is spread in the discharges (pus) from the nose and burst abscesses. Objects such as water troughs, feed buckets, brushes, reins and other equipment, if contaminated with infected pus, can also spread the disease. Recovered horses can spread the disease for up to eight months, even though they can appear clinically healthy and normal.
Wow! Strangles sounds like some bad stuff! For some reason, I thought that once they'd either had it or been vaccinated for it, that the immunity lasted a whole lot longer than what they said. I think my vet told me that, but I'm not sure. I vaccinated all mine for it last spring and was considering skipping a year, but I don't think I will now.