I give liquid Ivomec to the dogs for heartworm preventative as well as a general wormer. It is the active ingredient in meds like heartguard only I don't have to take out a loan to get enough for all the dogs!

I live in the South and heartworms are a big problem here! I only paid like 26 dollars for a 5oz bottle. You give 1cc per 20lbs. I don't give it during the Winter months. I start in the Spring and do it every month until the mosquitoes are gone. The Vet that cropped Uzi's ears taught me about it 15 years ago. I have been using it ever since and have never had a heartworm issue.
Many people get up in arms about it....but I have done research on it in the past few years (after someone told me I was going to kill my dogs) and there was nothing found that made me willing to stop. Like I said, it's the active ingredient in in heartworm meds sold by the Vet...it is also what is used to treat dogs that have heartworms. I'm just cutting out the "extra" ingredients and the middle man. I can buy it at my local feed store. This bottle though I bought the day Uzi got her crop....the Vet that did her crop sells it.
I do Ivomec 1% too. For anyone reading this,
never ever use Ivomec Plus. It has extra stuff in it to kill parasites in cattle...and dogs cannot handle it. It is the little dogs that people really have to be careful for and can over dose more easily like Jan said. Ideally, it would be better to dilute the amount in propylene glycol if the dosage is too small to draw accurately in a syringe. This is what they dilute the ivermectin with to make the ivomec 1% solution. Vegetable oil can be used but it's not as accurate as propylene gylcol because it doesn't mix as well.
As far as flea/tick we use a natural spray since we don't have problems with them. I make sure to heavily apply it/reapply and the stuff we use can be used on humans too. I also brush them right there at the park and have them lay in the grass while I go over every inch. Since owning the dogs and going this route, I have only found one tick on Paige a few years ago, and it was almost as soon as he was on her, not in embedded. I like the idea of the collar tag a lot, though!
You give 1cc per 20lbs. .
I did read that your vet taught you this 15 years ago but is this amount you are giving undiluted Ivomec??? I just wanted to point out to anyone reading this (and hey, maybe you are unaware and it may help???) that wants to be accurate as possible, that this amount is too much if it's undiluted. That is
10,000 micrograms per 20lbs...when it should be
66mcg/20lbs of ivermectin which equals 0.2cc... and that is a 30:1 dilution in propylene glycol! The 1cc per 20lb dosage you have, of undiluted 1% solution of ivomec (if it is undiluted), is just over 151.5 times more ivermectin than the recommended amount! I know dogs with demodex mange do get treated with a higher amount, sometimes daily, but they usually don't get demodex more than once.
I just wanted to put a word of caution out there and hope you understand since, there is discussion going on in this thread of concern over giving our pets toxins and trying to minimize the amount given. And hey, I'm no vet but the amounts match up with the amounts in Heartgard and I've run it by my vet and they were "ok" with the dosage so maybe you have some info on your dosage that I'm not aware of...? It's just good discussion to gather details and decide what's best for your dog from there on.
http://www.dogaware.com/health/ivomec.html#efficacy