Well, we've mostly eradicated very human-specific diseases. Some do also infect other animals, but we've generally targeted very specific strains and species that are pathogenic to humans. We haven't completely eradicated an entire family of bacteria, or large class of viruses, which seems like it would be more comparable to eradicating all mosquitoes of every genus and species. It doesn't seem that hard to imagine unintended consequences if we eradicated not only the plague bacterium (probably Yersinia pestis), but the entire family Enterobacteriaceae, for example.