Do you ever wonder why it is you administer heartworm medication to your dogs (and some of you, to your cats)? If you’re reading this I know you’re not illiterate. You can surely tackle the print on the side of a box with ease. However, did you ever wonder how common these wormy creatures are and whether you actually need to give a drug each month to kill it?
An increasing number of my clients do. Surprisingly similar (albeit less widespread) to the raging debate on vaccines, heartworm resistance is on the rise—and I don’t mean drug resistance. The one I refer to is a purely human phenomenon.
Ever since Filaribits Plus (back in the seventies and eighties) was found to cause devastating liver damage to some dogs and then Ivermectin (the active ingredient in Heartgard) was determined to be hazardous to the health of select breeds (collies and Aussies) a movement of anti-heartworm proponents has been slowly gaining ground.
No doubt, drugs are an imperfect way to deal with disease. Natural immunity is always preferred. However, dogs don’t have natural immunity against heartworms. The slithery things are much too smart for that. They have been living successfully inside dogs for centuries, perhaps even for millennia.
Heartworms don’t really aim to hurt dogs, they just want to have a place to live and breed. Killing off their host is an unwanted by-product of their lifestyle. Because dogs have only recently achieved a greater lifespan (due to their overwhelmingly successful interaction with humans in recent decades and the medical attention that comes with it) heartworms have become a more serious health risk, particularly to the geriatric population. But all dogs, even young dogs, are at risk for disease, even for serious reactions to the worms in some cases (such as liver and or kidney failure and, more commonly, respiratory disease).
For this reason preventative heartworm medication is a must for dogs living in climates that support mosquitoes. Year-round, monthly administration is by far the safest means of control. Eliminating mosquitoes entirely is impossible.
Some of my clients contend that heartworms are preventable via natural supplements that boost the immune system. No study bears this out. Some believe that controlling the mosquitoes (eliminating standing water in the environment and using citronella collars) is the way to go. But there’s no way to ensure that NO mosquito gets to your dog.
I even have some clients that boast that their dogs have never received a heartworm pill and yet have never tested positive. This is fairly common. It’s the rest of us that keep their dog free of heartworms by eliminating our dogs as hosts, thereby reducing the overall population of larvae in the environment. If that`s you, I hope I can help you reconsider.
Much like the issue of vaccination, it’s always safest to be the one unvaccinated animal in a population of vaccinates. Of course it’s best not to assume the risk of a reaction if you know that everyone else is protected and can’t transmit any disease to you. So it’s perfectly safe to not administer heartworm medication as long as the rest of the dogs receive their heartworm pills.
My contention, then, is that it’s our civic duty to keep as many dogs free of heartworm disease as possible by taking our dogs out of the host population with monthly medication. Sure, all drugs have their risks (I repeat that constantly in this blog), but the risk of heartworm medication reactions is miniscule by drug standards. The dose needed to kill larvae is teeny tiny; only one dog in about 5,000 reacts adversely (usually minimally) to these drugs.
If you don’t give your dog any other drug and you live in a mosquito prone environment, please consider this one—if not for the sake of your own dog, for that of all the strays that have no access to healthcare and might be helped by your generous contribution to the reduction of heartworm in the overall population. Thanks!
Dolittler
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The problem that I hear about the most often (as a volunteer rescuer) is the cost of the medication. Far too many dogs are surrendered to the shelter in my area, or come to the shelter as strays, that are heartworm positive. Even where owners want to provide the preventative, they can't always keep to a strict schedule because of cost.
I've been administering to my dogs the liquid form of Ivermectin that is supplied as a cattle dewormer for 15 years now. I learned about it from people who raise hunting dogs in the rural area that I live in, and my vet helped me figure out the proper dose. It costs about $35 for a 50 ml bottle, a bottle that will last for years. Why is this option not better known and accepted? Is it because it is an "off-label" use of the drug?
Rita
Rita October 3rd, 2006 07:51:00 AM
This is absolutely fascinating. I hope you'll explain the differing advice about the 9 months vs year around Heartguard (well, that's what I used when I had a dog). My dog never had a problem with heartworm or the prophylactic, but when I get another dog, I'd like to understand what's best.
I'm really enjoying your blog, by the way. Great stuff, and great storytelling.
Bardiac October 3rd, 2006 10:36:00 AM
Regarding the cost - we started using the new generic form of Heartgard Plus, called Iverhart Plus. Our vet doesn't volunteer the information that they carry it, we have to ask, but it saves us lots of money since we have several large dogs.
We use it every month of the year in South Alabama. We're not willing to take a chance that there might be even one mosquito in the middle of winter.
Margie October 3rd, 2006 11:28:00 AM
I agree that it's more about cost than a philosophical issue about "natural" care. Consider the number of dogs coming out of Katrina who were heartworm positive. I've lived in the Deep South (Florida Panhandle). It's an economic/education issue.
Still, I wish more veterinarians would volunteer the off-label use of cattle Ivermectin. It's cheap as dirt, and it could save many pet lives when money truly is an issue.
I write about "the minimums" of pet care here:
http://spadafori.typepad.com/woof/2006/01/what_are...
Gina October 3rd, 2006 11:45:00 AM
This is a fasciniating issue Dr Patty and I want to thank you for bringing it up and discussing it.
If cats are susceptable to heartworm as well, why have I never heard of heartworm preventative for them?
And if it is strictly a cost thing (which I don't think should be an issue as when you adopt a dog you should carefully evaluate your finances to ensure you can provide it with the best of care in this case heartworm prevention but I digress), why aren't there less expensive alternatives. Its easy for me to go to the drug store and get real motrin or the Life brand version of the same drug and save money.
Just a few thoughts.
Shannon
Shannon October 3rd, 2006 01:16:00 PM
Rita: What you're doing (assuming you're using the right dose) is pharmacologically appropriate. It is not, however, approved by the FDA. A vet could get in trouble for telling you to use it. If we have even one product on the market approved by the FDA for heartworm prevention then we are legally compelled to use that product first.
Dr. Patty Khuly October 3rd, 2006 10:10:00 PM
Bardiac: The number of months a year corresponds to the presence of mosquitoes. If you have mosquitoes year-round then you use the product for twelve months. If you live further north, then six months might be appropriate. Check with your vet.
Dr. Patty Khuly October 3rd, 2006 10:13:00 PM
Margie: Iverhart is a perfectly good alternative to Heartgard. See my answer to Rita for an explanation on the Ivermectin thing. I agree that Ivermectin should be made available to shelters for maximum cost-effectiveness.
Dr. Patty Khuly October 3rd, 2006 10:16:00 PM
Gina: I combined my answer to you with that of Margie's. I wish we didn't live in a society where the use of a perfectly acceptable drug becomes problematic due to the byzantine nature of the government (and society's love for the lawsuit)--but here we are...
Dr. Patty Khuly October 3rd, 2006 10:20:00 PM
Shannon: Cats are not the hartworm's true host. If cats get infected it's an "accidental" infection. The stats on incidence of heartworm in cats are very difficult to interpret but I just don't think anyone really knows how big a problem heartworm is for cats--that's the bottom line. We assume it's a pretty rare thing but--who knows? If yprice is not an issue, consider Revolution or Heartgard for cats. If your cat lives outside, it's a no-brainer: Revolution takes care of all basic parasites and heartworm.
And as to your second comment: Amen.
Less expensive alternatives: See Margie's Iverhart comment.
Dr. Patty Khuly October 3rd, 2006 10:25:00 PM
I like it when you talk about controversial topics like this. Now, of course, I have to give my own opinion. :)
<a href="http://web.archive.org/web/20050307092438/http://www.bullovedbulldogs.com/heartworm.htm">This</a> is one of my favorite sites about heartworm. It leans towards natural prevention, but I think it's pretty balanced. It also does a great job of explaining the life cycle of heartworm.
I really don't like that the drugs are called heartworm "preventatives", since then it gives the impression that your dog will never get heartworm (of any stage) if they take them. In reality, the dog can still be infected, it's just that the drugs kill various stages of the parasite--they are essentally poisons. So there's never much of a chance for the heartworms to become full-blown adults.
I personally do not give heartworm preventative to my dog, but then again I live in the SF Bay Area, where mosquitoes aren't usually a problem. Even my (allopathic) vet said that she's okay if people decide not to use the preventative. If I moved to an area where mosquitoes were more of a problem, then I may reconsider my decision. However, I think I'd be more inclined to just do a heartworm test every six months instead of giving a drug every month. From what I've read and understand, heartworm is fairly easy to treat if it's caught early. I also believe that dogs with strong immune systems aren't likely to get life-threatening infestations--as you said, it's not in the heartworm's best interest to kill its host.
But that's just me, and I realize the risks I take with my choices. I also realize the benefits. I don't believe that my dog's immune system can ever be truly healthy if I am giving her drugs every month.
And just in case I haven't mentioned it yet, I really love your blog, and I do find it very informative as well as interesting to read. So thanks for taking the time to write! :)
Janine October 4th, 2006 01:35:00 PM
Oops, looks like HTML doesn't work. Just be sure to copy/paste the entire link there, not just the part that auto-linkified.
Janine October 4th, 2006 01:37:00 PM
I find it hard to believe that mosquitos are not a problem in the SF Bay area when Yolo County, just inside the valley, has a very high rate of West Nile Virus infections.
Natalie October 4th, 2006 02:49:00 PM
I personally haven't seen many mosquitoes where I live. But I live in an suburban area.
This map shows heartworm risk in the US; the Bay Area is green (<1%):
http://cal.vet.upenn.edu/merial/hrtworm/images/usc...
Janine October 5th, 2006 01:53:00 AM
The discussion continues on Dogged:
http://www.doggedblog.com/doggedblog/2006/10/pick_...
Gina October 5th, 2006 12:57:00 PM
I,too, consider heartworm meds not a "preventive" but a poison. I refuse to give it to my boys. My standard poodle is in very obvious distress for several days after he was given his Interceptor pill. He would pant, pace, and he had a panicky look in his eyes.
So instead of poisoning him every month, I get him tested twice a year. Then, if he tests positive, I will at that time treat him .
Just because the government or a company says it's safe don't make it so. My dad served in WWII and was in Japan right after the bombs were dropped. The servicemen were all assured that there was no risk.... my dad died of cancer of everything....it's amazing that if enough people say it's true, we tend to believe a lie.
Agadore's momma March 25th, 2007 12:39:00 AM
I came across this article dealing with Seasonal Heartworm Medication Schedules. Have you read it or heard of it, and what is your opinion of their conclusions?
http://www.journals.elsevierhealth.com/periodicals/ysvms/article/PIIS1096286798800108/abstract
If it takes 6 months for a larva to become an adult, wouldn't dosing a dog for HW every three months give just as much protection, at less dosage total, than dosing for 12 months straight, especially during times of year when mosquitoes aren't even active in many regions?
Pai March 1st, 2009 03:43:58 PM
I have two dogs one was adopted from a shelter and the other I purchased. I give them interceptor as a heart worm preventative. Normally I do on the same day (26th) of each month *but* sometimes I forget and I give it to them a couple days sooner or a couple days later. Could they potentially get infected if it is not done exactly every 30 days?
Thanks,
Juan
Juan May 26th, 2009 11:31:01 PM
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