Simon is quite correct.
Fatality due to conflict is not common but the hounds occasionally get a clawed slap which keeps them respectful.
The question is why would the leopard- possessing superior strength, ability and bite force evade the hounds by climbing a tree? Why not simply kill them all continue down the path unbothered?
Well the fundamental criteria for the continued existence of every individual predator is to maintain physical health and avoid injury. A drop in condition compounds the effects of external and internal parasites and disease weakening the animal in turn affecting it's hunting capability and reducing it's protein intake thereby perpetuating the spiral. So the risk of any injury is cause for avoiding conflict.
On the other end the hounds have benefitted from a relationship with man that simulates a social pack with benefits like constant caring. The effects of injury are less threatening to the hounds as they have a support structure that will care for them. So although their deep instinct is to pursue game and not competing predators, they can be trained to exclude all other scents but those of the leopard and overcome the injury risk calculation.