There is no harm in treating an animal with alcohol, because when an animal eats an impure substance, – in this case we are saying alcohol- it does not make the animal forbidden. In fact, the animal meat is permissible as long as the effect of that impure thing is not visible on it. In fact, the most sound opinion among the saying of Islamic scholars- may Allah have mercy on them- is that alcohol is not impure, thus, if there is a need and a benefit that the specialists recommend, there is nothing wrong with it.