Horse thrush is a bacterial infection induced by excessive dirt and stuff in the frog of the horse's foot. Thrush has a very distinct smell and the horse is probably going to have a sensitive middle area of its hoof and maybe also the wider areas of the frog. Splits in the tissue with darkened areas are an usualy indication of horse thrush.
Most people don't have spare cash to shell out on keeping their horse thrush-free so it's possibly good to know that there are methods to look after your horse on a tight budget should thrush strike. Antiseptics can assist and a lot of people use Betadine, Kopertox or Thrush Buster. Perhaps a bit ov an overkill and not ideal, some people even apply bleach or hydrogen peroxide. It is however important that care is be taken so as not to do more harm by employing the wrong product or chemical.
It's perfectly possible to treat your animal yourself if the situation is noticed in time. Although, if your animal appears to be looking lame then you should consider calling on a vet. You should not leave it for too long because it will severely damage the foot of your animal.
Daily inspection of the frogs of the horse's feet is a good prevention against thrush. Proper foot care with a hook knife and perhaps a miniature wire brush to clean out the cracks in the animal's feet is important to make sure that your horse does not get thrush.
Preventing thrush is important and keeping the horse away from soft and muddy areas for prolonged periods is advisable as is making sure that the stable is kept clean. You need to ensure that your horse doesn't collect a build-up of muck in it's feet. That's your best chance of towards maintaining your horse thrush-free.