Sorry to hear about the heartworm You did everything to prevent it and I thank you for sharing this...thought ivermectin was fail proof for this. Hoping your baby will be okay!
We are using Advantix for flea/tick/mosquito and for now are still on heartguard/ivermectin until we do a follow up blood test on them to see if we are still seeing the microfilaria (baby heartworms---for those who may not know, the ivermectin will NOT kill the adults but is supposed to destroy they immature ones so if we are seeing the mf, the drug is not working).
She was weighing options for us for what to switch over to and is still talking with southern labs to see how they are testing for resistance.
She should be fine in the end and right now is furiously telling off the trains going by in the distance.
Our current vet only has heartgard... since our pup is part herding dog I changed her to interceptor after checking the ingredients.
Interceptor has Milbemicin I think.... it's by Novartis. And can be used for slow kills also. It's what the vet I worked for preferred.
Thanks promiceacres. I will ask her about that. There were a few chemicals she mentioned but I don't recall that one---she might have said it but it was a lot to take in.