Oh, yes it is!
While I agree the borders need to be protected from illegal humans (pleasse don't send them here), there are many danges posed by animals. Ever heard of Bird Flu, Congressman? How about West Nile Virus? Leptospirosis? All carried and transmitted by birds.
And just what do you attribute the recent revival of POLIO and TUBERCULOSIS to? The ILLEGAL INFILTRATORS bring disease too, but I guess they bring the diseases "other American's aren't willing to contract"!
If it's bad for the animals to illegally enter...why is it ok for the populace?
Infectious diseases carried by non-human animals are much more transmittable to other non-human animals than to humans. While people have (or can develop) immunities, can be vaccinated or treated, animals cannot, and the resulting epidemic(s) could devastate the food supply. There is much work to be done on many fronts