Repeated giardia infections (I think)
Before getting into the issue, I want to make sure to point out that I've been in constant contact with my vet regarding this, but I'm hoping to crowdsource some additional ideas.
Back in May, I adopted two barn cats (I posted about them previously). Due to one cat being extremely aggressive, I've had them separated for a few months now. And they are "barn cats" in that they live in my covered, heated, sealed garage (3,600 sq. ft.) - they do not go outside AT ALL. I feed them wet food three times a day, plus leave dry food and water (which I change out every 3rd day) for them.
I've watched both cats play with mice that make it into the barn, to the point that they'll kill the mouse and leave the body - I haven't seen either eat a mouse, I've found no carcasses that have been chewed or pieces of mice. I understand that doesn't mean they don't eat them, but I've cleaned up probably 10 dead mice and none have shown any signs of being eaten, just killed.
Anyway, shortly after getting the two cats one of them - Theory - had bloody diarrhea. I took her to the vet and they found three infections, including giardia. We gave her Panacur granules, plus had to dose her twice a day for two weeks with methimazole liquid. Being a skittish barn cat, it was incredibly stressful - hard to catch, hard to get her to settle down, etc. We did the best we could, and the problem went away. After medication, we took a sample back to the vet and it was tested and found to be negative, so we were good.
Then, about 4 weeks later, it happened again - bloody diarrhea. I took her back to the vet, she tested positive for giardia again, so we did the Panacur granules only, this time for five days instead of three. Once again, the problem went away. I took a sample to the vet and it again tested negative.
She's been mostly fine for the last three weeks - I say mostly because about a week ago I was cleaning her litter box and as I scooped some of her poop into the bag, I thought I saw something black in it, like maybe a spot of dark blood. Then today, she had bloody diarrhea again. I just took the sample up to my vet for them to test and am waiting for a call.
It's possible that something else is causing bloody diarrhea, but the vet (actually, two different vets at the same office) both attributed it to the giardia. I'll know a little more later today, but trying to figure out where she could be getting it? I know that standing water is a usual culprit, but that isn't an issue - indoor only, freshwater changed regularly.
The vets both told me that giardia can be hard to get rid of, so I don't know if she keeps catching it or has never gotten rid of it. And if she's had it all along, then that leads to two questions: 1) why did she test negative after medication both times and 2) why did the symptoms go away?