When i had Julz as a puppy i gave her Heartguard for the first few years, she has not had it in the last 8-10 yrs and her Dr. told me since she was basically an inside dog that she would be fine.
When i was yonger we never gave heartworm med's to our dogs and they were okay without it.
I don't know if where you live has anythign to do with it but i am in FL.
My fingers are crossed that all works out for you and you pups
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