Join Date: Aug 2009
Location: New South Wales, Australia
There is no vaccine, treatment or cure. Once a horse is confirmed as having the Hendra virus they are euthanased.
They are a spread through Fruit bats (I believe - some kind of bat), and the horse generally catches it by consuming food or water that have been contaminated by the bats excrement. At least that is the main theory I have heard, there has been basically no research into this disease, as the government demands that the bodies of infected horses be cremated instead of being studied.
Having said that it seems a fairly rare disease, but it is very scary. I guess the best way to prevent it would be to have your horses away from the flight paths of bats, and away from fruit trees that may be food sources for these bats.
There are more precautions you can take to minimise the risk of it being transferred to a human, but honestly with the amount of space (paddock) a horse occupies it would be very easy for an area to be contaminated without the owner being aware of it.
As I said its rare, you're horse is much more likely to die of a snake bite than Hendra - as far as probability goes.