Heartworm is a yearly jab these days. The worming is of intestinal worms. Heh, my chi, Tiffany, needed the monthly tablets. She LOVED chicken hearts so I would cut a slit in one, insert the little heartworm tablet, put it and the rest in her dish and she would eat it all up. One time she saw me do that, after that the tablet was left in the dish when the hearts were finished. Got a couple more down her in a blob of leverworst or butter but, nope, stopped taking even them. So suspicious! After that it was force, not too hard with a chi which struggles to break skin in a vicious bite

Then the yearly shots came in, phew!
The heartworm jab stingsโdog will accept the parvo etc shot without much protest, WWII erupted when the heartworm jab was started. Last jab she had Demi had to be wrapped, a muzzle was not enough.