As an aside from, it’s better to have your dog SNAP tested for heartworms and treat them *only* if they become positive.
Heartgard is not a very good wormer as it totally misses whipworms, which are just as deadly as hookworms and has too many side effects for my comfort.
Better to dose everybody with Panacur every month or two to knock out intestinal parasites and check for heart worm a couple times a year.
[oh, yeah, *this* heretical post is gonna get me some blow back, I bet]
:)
I would never contradict you on any dog issue, but heartworm prevention is dependent on geography, among other things.
My sister is a mega-dog lover and has several, along with numerous other animals. She and her husband own a horse farm in central Florida.
Where she lives, it's not a question of if a dog gets heartworms; it's when. All untreated dogs who spend even minimal time outdoors get heartworms sooner or later, and it's usually sooner. She treats all of her dogs year round.
Where I live (Kentucky), heartworms are somewhat common, but a dog that spends most of its time indoors may be able to forego heartworm treatment. My dog spends a fair amount of time outdoors and I live near a creek, so I give her a preventive during the warm weather months but not in the winter. Heartworms, as I'm sure you know but others may not, are mosquito borne.
BTW, ivermectin should never be given to collies. I don't know why, but my vet confirmed that. I don't know if that includes Border Collies--which is what I have--but to play it safe, I don't give it to my dog.
BTW, heartworm preventives work backwards, not forwards. They get rid of any heartworms the dog may have picked up over the last 30 days or so., but will not prevent the dog from picking up the parasite in the month going forwards.
That's my understanding of the issue, anyway.