Wouldn't a human who is allergic to human DNA have health problems?
That is basically what auto-immune diseases are.
As for the original topic (necro'd as it is) it's . . . actually a really intriguing idea, if the Yeerks went about it the right way. But, don't think about it as an end goal, of obtaining non-sentient animal hosts. Think of it as a means to an end, of obtaining more
human hosts.
Gorillas would technically work for what I have in mind, but they might not be the best option. Dogs (and I'm assuming here that they have bigger brains than horses and thus would be infest-able) would work so much better.
So . . . the main reason the Yeerks almost never transfer themselves from one host to another via ear-to-ear contact, is because the newly freed host would attack, blab, or at least make a run for it, right? Whenever a Yeerk switches hosts, they either have to have a new Yeerk ready to take over, or find a way to discreetly murder the original host.
With non-sentient animals, this is no longer a problem. Even if you assume the animal is smart enough to realize that the thing that was controlling it is now inside somebody else, it still probably won't know what to do with that information. Thus, a Yeerk inside such an animal would be perfectly free to simply bear-hug the nearest human and make the switch. Even if people were watching, nobody would be able to guess what was going on.
Like I said, a (captive) gorilla would work, particularly if the Yeerk was looking to infest the gorilla's zookeeper. Or maybe they could stage an 'escape' from the zoo, and 'attack' somebody (all that would end up in the news would be 'such-and-such person was attacked by a gorilla!' and nobody would be the wiser about what really happened).
But, the real potential here is dogs. Super-easy to capture for infestation, you just dress up like (or infest) a dog-catcher and play catch-and-release. And probably about half of the human population owns a dog. Sure, owned dogs are supposed to be subject to leash laws
for exactly this reason, but nobody really follows those. Step one, catch and infest a dog. Step two, snuggle your head adorably against your master's ear, while the human is sleeping for best results. Step three, re-infest the dog and repeat for remaining family members.
Bonus points if the Yeerks are able to identify and selectively capture the dogs owned by influential people.
P.S. Yeah, this is probably a silly idea. But it still beats Yeerks-in-cell-phones!
