If you dewormed your horse in June and it's July, for example, you don't need to deworm them again.

如果你在6 月和 7 月为马驱虫，那么你不需要再次给它驱虫。

You can cause harm by deworming a horse when they don't need it because we can actually cause resistance against the medications that we use to deworm horses in those parasites that do exist in the environment.

在马不需要的时候给马驱虫会造成伤害，因为我们实际上可能让马对我们用来驱虫的药物产生抗药性，而这些寄生虫确实会存在与环境中。