Riddle relevant to this thread:
The bite of which animal has killed the most humans throughout history?
The mosquito (I can't back this up with references, but it sounds about right). The black death killed a bunch of people at once, but malaria is more of a "slow and steady wins the race" killer.
Protection from Insects should also work (or there should be another spell that instead works) on animals. Flea and tick protection for your animal companion, or keep the skeeters off of ya. Might be good for bee-keepers too. Need to specify very carefully what sorts of swarms it works on. Don't want it stopping hardly anything that even hits CR 1, but I would think that if you limit it to naturally occurring (rather than magically summoned, or extra-planar) swarms of less than X HD it should work. I have no problem with a 0th level spell protecting a single character from killer bees encountered due to a failed Survival roll.
Precious Alarm, Mass has "levels" where it should be "level" for the targets.