The word "animal" is often used to mean "non-human animal." Context is key. I bet your locality has an Animal Control department, and you understand from contex

The word "animal" is often used to mean "non-human animal." Context is key. I bet your locality has an Animal Control department, and you understand from context that it referes to non-human animals. Jumping species tends to be a rare event with regard to diseases. But it is an important event, hence the article.