Louisiana-based breed rescue here -- we're in one of the highest HW areas in the country, and most intake dogs are either already positive or will turn out to be so in 6 months or so (as you can't really trust a negative test result until you get at least two negatives 6-7 months apart if dogs have been off prevention/stray). We manage it on a shoe-string budget.
We've been using the Doxy + Advantage Multi protocol to clear HW infections for 10+ years. I think of it as "medium-fast" -- it's not super-fast like immiticide or super-slow like ivermectin. It's right in the middle. It used to be vets who didn't deal with a lot of rescues scoffed at it. A few Northern vets even fussed at our adopters who move up there -- the vets thought we were crazy and it was "impossible" that this protocol would work as fast as we said it probably would. But the rural South Louisiana vets who first figured this out were right -- and the research now proves that it works.
I've attached a 2019 article to share with any shelter or rescue vets who push back on doing this -- they need to read it. (There's another one in the same journal from 2015, with a member of the AHWS board as a co-author discussing "immature" HW, but the one I attached examines effectiveness on ADULT HW). This is NOT the old ivermectin slow-kill protocol -- Advantage Multi is the ONLY prevention product that builds up to a steady state in the serum after 3 months, so it's constantly bombarding the HW with moxidectin (instead of being cleared by the liver in between doses). If the vets look at the pharmacology of how Advantage Multi differs from oral meds, they'll start to understand why the worms start dying around the third month on it.
We've learned a few things along the way. First, the 30 days of Doxy needs to be at the "heartworm dose" not the lower "kennel cough dose" -- something like 10 mg/kg day (divided in half, 12 hours apart, with a meal) -- but run that by your vet. The benefit of that higher dose for the full 30 days is that it not only starts the HW treatment (with a big anti-inflammatory punch in the lungs from the Doxy), but it also knocks back subclinical tick disease that you don't know about. You might not ever know that you saved a dog from RMSF by doing that long, expensive round of doxy during HW treatment (instead of just 2 weeks of it), but it will be happening with some of your dogs in the background. The two-week alternative doxy program won't give you that extra layer of tick disease protection like the 30-day program. I'm totally convinced that the 30-day protocol saves money in the long-run because it's doing multiple good things for dogs exposed to multiple disease vectors.
The cheapest price we've found for BIG dogs for Doxy is Wedgewood Compounding Pharmacy in NJ -- they compound 300 mg and 400 mg chicken-flavored wafers that are scored and easy for fosters to cut up (e.g., to give half in the AM and half in the PM). They'll only give the price to a vet, but any shelter vet or private vet working for rescue can have a tech call them for pricing. It's cheaper and easier than fooling with several 100 mg capsules for big dogs getting large doses.
Advantage Multi just went generic, so you can now buy off-brand versions of it--Allivet, Chewy, etc. all have alternative cheaper versions of it now. One little-known bonus benefit of it is that in addition to being pretty decent flea and intestinal worm prevention, it also kills rat lungworms -- dogs that eat frogs and snails or rats can get those, and they can cause meningitis-like symptoms that most vets won't recognize as a parasite, so it's an extra weird thing you won't have to worry about (and, yes, they're in the Deep South--we had a dog come out of New Orleans canals with one of the first canine cases in Louisiana). It's also the only prevention product that has zero documented HW resistance in the Gulf states for the new ivermectin-resistant strain of HW that's emerging (see the Auburn study for more on that).
We've used Advantage Multi to treat hundreds of dogs -- it works, if they stay on it post-adoption. The vast majority of our HW+ dogs have had a negative HW test in 1 year after their first dose (but that means they cleared the worms several months before, as it takes a while for antigen to decline). We've had a few that cleared in as few as 6 months, and a few that went out to 18 months, but it's basically a bell-curve, with most dogs right around the 12-month mark.
I really like the Doxy+Ad-Multi protocol because the worms die slowly -- so the side effects are greatly reduced. If the dog starts coughing in this phase, it needs some pred, and possibly an xray to make sure that it's a good candidate to continue -- if its disease is so advanced that the dog is at high risk of Caval Syndrome, it may need fast-kill protocol instead, but that's been very rare in our experience. If they're going Caval, they might even need surgery--pulling worms out through the jugular vein one by one. Our rescue's vet is one of the very few in our area who has done that surgery successfully many times -- a lot of clinics won't do it.
I've known some vet clinics in South Louisiana using Pro-Heart on HW+ dogs to kill the worms, but I wouldn't do it. If you look up the insert for Proheart, it has a black-box warning that it should only be used on young, HEALTHY dogs. ProHeart was pulled off the market in 2008 because of reports of dogs dying, and it was required to carry the black-box warning when it came back on the market. That's enough for me to wary that we'd end up with worms dying off quickly and causing an emergency that puts a dog in the vet ER ICU....which means several thousand dollars to save the dog. I'd rather minimize those risks!
For those who do fast-kill treatment with immiticide, it's not a walk in the park. It's arsenic-based and extremely painful--they NEED pain meds after those injections. It usually requires an over-night at the vet, and then rigid crate rest. My breed is also side-effect prone, with at least 10% of them getting into respiratory distress even following the crate-rest protocol, and we've known several that died when they threw a clot in the lungs during the AAHA treatment protocol. When that happens, they start coughing up blood. It's an emergency, and they have to be put in an oxygen-crate in a clinic with ICU, and prognosis is poor. We haven't had these sorts of emergencies with the Doxy-Ad-Multi protocol -- and while the "party line" is that heartworms keep doing damage during this treatment, I've known many GSDs live to a ripe old age having done it, so I'm not convinced that the risk-reward really favors the fast kill protocol -- the 2019 paper attached below supports that.
Shelters and rescues can also cut the cost of Ad-Multi by buying the big-dog tubes (88-110 pounds), emptying them into a vial, and then pulling the correct dose for smaller dogs into a needle-less syringe. A vet can calculate the exact dose per pound for you, or you can look at the breakdown of the Ad-Multi cartons and figure it out very easily. It works out to costing a lot less (and you don't have to stock lots of different sized tubes, unless you're handing them out to fosters).
------------------------------
Maggie Thomas
President
Red Stick German Shepherd Rescue
------------------------------