Neither do I, nor was it intended that way. I am merely trying to give Gail some options to consider, and if she wants, to discuss them with her vet.

I tried to find valid studies and such, bc I know you like to see that stuff, but I must not have access and am limited in what I do find.

I think her vet could find documentation and would before doing anything I suggest... and I would totally expect him to do so. If she chooses not to consider anything I've posted, that's fine too.

And an FYI: The active ingredients in Denamarin are prescribed quite frequently for humans with liver problems such as Hepatitis.

I am very aware of Denamarin and had a pup that was on it years ago. :)

Wolbachia - Wikipedia, the free encyclopedia

Effects of doxycycline on the endosymbiont Wolbach... [Vet Parasitol. 2010] - PubMed result

Combined ivermectin and doxycycline treatment has ... [Int J Parasitol. 2008] - PubMed result

Wolbachia bacterial endosymbionts of filarial nema... [Adv Parasitol. 2005] - PubMed result

Here's the beagle Doxy study!
Heartworm and Wolbachia: therapeutic implications. [Vet Parasitol. 2008] - PubMed result

DogAware.com Health: Heartworm Disease in Dogs - Prevention and Treatment

Wolbachia-lives symbiotically inside heartworms. | Medical Reference


Oh, I couldn't tell by your posts...:)

I am not going to read every single one of those links. What I read and refer to in this post is the study done at NIH (see second link you posted). What I gather from that study is just what I said previously. That they believe that the Doxycycline's effect on the Wolbachia organism is interferring with the transmission of heartworm disease, not the direct effect on the worm itself. If anyone sees something different in the below referenced quote from the NIH, please explain it to me.


Effects of doxycycline on the endosymbiont Wolbach... [Vet Parasitol. 2010] - PubMed result

The effect of the antibiotic therapy on the worms may have interfered with the transmission of heartworm disease because the population of microfilariae and the number of microfilaremic dogs were reduced and the microfilariae positive samples that were found did not test positive for Wolbachia sp. in many cases. These findings suggest that in areas were doxycycline is extensively used D. immitis transmission may be impaired by the reduction on the number of microfilariae and on the endosymbiotic bacteria in the larvae turning them incapable of completing development once they infected a new host.

As to your last comment, let me simply say this: Just because something such as Denarmin has an effect and is indicated in certain illnesses that effect the liver, it does not to me indicate a wide usage of such product. I am a firm believer that "if isn't broke, don't fix it". Denarmin, while good for liver compromised dogs, IMO should not just be used because someone "thinks" there could be some sort of effect from a medication. I simply believe that many people go completely overboard with things that they want to believe are totally harmless. I have seen people become ill from overdoses of vitamins. I also am totally astounded at the numbers of people who continue to say that Heartgard is harming dogs' livers. Then, so many who read that stuff, don't give preventatives and the poor dogs suffer. Fear mongering to me...plain and simple. I have been giving Heartgard to my dogs for many, many years now and none of them have compromised livers, thank God.

Wow lots of back n forth. First Zoey is NOT going under any slow kill method, instead she will be having the combined Heartguard Doxey for 2mths prior to the adulticide treatment, which she will be hospitalized for at least 2 days for.

She is on a regime where wkly she gets what would be the normal Monthly dose of Heartguard, and on a daily regime of Doxey. And I am very scared about the adulticide treatment, but she must have it; so I shall pray and cross every finger n toe I have that she will come through the treatment like the trooper I know she is.

Believe you me, I am of the nature I want this invader out of her body NOW, but due to the studies I've read that Doxy + Heartguard for 2-3 months is much safer, for the dog, prior to the adulticide, then of course I would do this. In fact I insisted with the specialist that this happen. Please keep in mind that in 2009 there were only 586 dogs in Ontario that tested positive for heartworm; it is still not a "big" deal here. In fact my "specialist" had only ever treated 6 dogs before for heartworm infestation.

And for those that continue to advise me for year round treatment, I will re=iterate a reasonable response; that year round will be balanced against kidney and liver functions being evaluated regularly.

And btw I do know whereof I speak; I get monthly blood tests to evaluate liver function due to the strong nature of the drugs I am on; I have RA = Rheumatoid Arthritis. To date despite having been diagnosed over 15 yrs ago, I have managed to be on these poisonous drugs only one year.

The only thing left for me to say is that I have never seen a pup with liver and/or kidney issues related to heartworm preventatives. I have never seen any research data that indicates the necessity of such testing when vets prescribe these preventatives. And, lastly, it worries me greatly that there is so much fear mongering about heartworm preventatives. I believe there is more of a risk of a dog contracting heartworms when not protected than there is of a liver issue from being given a preventative.

As to testing ... my vet does lab testing on all of my pups yearly. I believe that to be a good standard of care. I go to my doctor for my yearly and take my pups for the same.

I don't understand why you would be reticent to give your dogs HW preventative year round when you already have one dog that has been diagnosed with HW and now will undergo treatment. I too hope you reconsider your stance on this. There is no valid reason to forego this preventative the benefits of which greatly outweigh any perceived risks.

Best wishes.

The only drug used in this study was Doxycycline. If they're not killing the adults with Immeticide, then the reason for the population of microfilaria being reduced is that the Adult Heartworms cannot breed and make more microfilaria.

The microfilaria in dogs treated with Doxycycline is affected by the death of the Wolbachia (caused by the Doxycycline) "turning them incapable of completing developement" (if they cannot reach adulthood, they cannot reproduce).

IMHO, these findings are saying that treating Heartworm positive dogs with Doxycycline can effectively limit the spread of this disease.

I believe the purpose of using Denamarin (which is harmless in dogs with uncompromised livers and improves liver function) along with Heartworm preventatives is to give the liver an extra boost as these medications go through the dogs system. Any medication given to a dog causes the liver to work harder, as it now has the medication to process and eliminate from the body.

This happens anytime anything, including food, is ingested by a dog. The liver works to remove what the body does not need or by products from what it has taken and broken down.

Many things that are eaten by dogs can cause liver cell death. The liver produces new cells to take their place. This is what the liver does. Denamarin (and similar products) have been proven to prevent liver cell death and supports the liver in the regeneration process.

I may start using Denamarin for all my dogs, when I give them their Heartworm meds. I am going to talk with my vet about it first, before I make any decisions. I am considering this option, as Dr Dodds recommends giving it, and I respect her opinions on such things.


Because of my fear of Heartworm Disease, I too was under the impression that more is better, hence my decision to treat my dogs year round. Thank you for starting this thread, as my current research has taught me that this is not necessary for the area in which I reside, and I now feel very comfortable with giving my dogs a break from the unnecessary medication over the winter months.

From what I've read, the plan for Zoey sounds very good. The Doxy will weaken the adult Heartworms, stop them from reproducing, and prevent any microfilaria from growing to adulthood, the increase in the frequency of the Heartgard will begin to kill off some of the weakest adults, and the Immiticide will kill the rest of them.

I was unaware that you were suffering with RA. I do know that it is very difficult to manage, and I truly wish you the best of luck with that. I will keep you in my prayers, along with your pups.:D

Well, I think I've said about all I can about heartworm disease and preventative. The bottom line is that I will use preventative year-round and try my very best to help my dog avoid deep and very painful injections of arsenic.

Any drug can cause side effects including liver damage. So if we start giving Denamarin before giving heartworm preventatives, then we would need to do that before giving any and all drugs. I suppose if that's what an owner wants for their dog(s), then that's their choice. However, we could apply the same theory to glucosamine and joint health, Azodyl and kidney health, mega doses of omega 3 and skin/tissue health, enzymes and pancreas health, probiotics and intestinal health, etc., etc. And you'll have a dog living on completely unnecessary supplements. That isn't standard of care and it isn't what I consider good medicine. It gets out of control very quickly. To each their own. Just as I don't take SAMe and milk thistle daily (because I take drugs), my dog(s) won't either unless there is a diagnosed liver problem.

Also, animals can and do get heartworm disease even in places wehre it freezes. It is showing up here during the winter when owners stop the drug. What each owner does is between them and their vet. I can't and won't agree that skipping preventatives during the winter is okay. And besides, tehre is now concern over the new MP3 strain. The best chance that the older preventatives have at killing the larvae are if the preventative is giving for three months consecuively after infection. So if the dog gets infected in October and the drug is stopped for the winter in November?? This may become more of a concern when some data is released about where this strain has spread to.

And btw, Ellie's post bile acids have been up to 106. That doesn't even come into the year-round vs. half-year equation. Her liver would be in much more rouble if I had to have arsenic injected into her.

How many months do you stop the medication? In Maryland, I can't imagine it would be more than 3-4 months. I don't see how 3-4 months, or even 6 months off, would dramatically reduce the risk, if there is one, of detrimental effects of heartworm preventatives. If damage is a concern, test annually. :confused:

Crystal, I agree, it is up to the individual to make decisions with the vet.

Admittedly, I initially committed to year-round Interceptor for some of the other things it covers. The more I read about HW and the more weather and pest anomalies I see, the happier I am to keep doing the preventatives going all year.

It is a shame it cannot be up to the poor pups and the vets. :( The poor pups have no say in their own care. That is all I have left for this thread other than....

I will continue to pray for Zoey and hope her heartworm treatment goes well.

As I said I have nothing more for this thread; but I need to address this that I saw after I posted. I am not going to banter with you on this topic. I read the study and see nowhere that it says that the conclusion was the weakening of adult heartworms.

From the site...below...and I remain convinced the study had to do with the effect of Doxy on Wolbachia. If it were so effective against heartworms, that would be a breaking development and the end of immiticide treatments! I have not heard that forthcoming.


Doxycycline treatment did not alter the detection of adult parasite antigens with the exception of two animals, though the number of animals carrying Wolbachia sp. DNA decreased, despite the presence of the microfilariae.

DogAware.com Health: Heartworm Disease in Dogs - Prevention and Treatment

Doxycycline should also be given to dogs that are being treated with monthly Heartgard (slow kill method) or any type of alternative heartworm treatment method, as it will weaken the heartworms, prevent them from reproducing, and reduce the chance of adverse effects caused by the heartworm infection itself, and by the worms dying. Wolbachia will repopulate over time, so the treatment with doxycycline should be repeated intermittently. A study on cattle infected with onchocerca volvulus (a filarial parasite similar to heartworms that cause a disease called River Blindness) showed that the Wolbachia repopulated within six months following short-term (two week) daily treatment with oxytetracycline. A combination of this short-term treatment with long-term intermittent treatment (double the dose, or 20 mg/kg, injected once a month for six months), eliminated 80% of the adult female worms as well as sustaining the depletion of Wolbachia. See this abstract for more information. In dogs, this might translate to giving doxy for two or three weeks at normal doses to start with, then repeating the treatment at twice the normal dose for one week out of each month as long as adult heartworms are present. The double dosage (10 mg/kg twice a day) is used to treat tick disease, so it is safe.

Wolbachia-lives symbiotically inside heartworms. | Medical Reference

Studies indicate that this parasite contributes to the adverse effects of both heartworm infection and heartworm treatment, including inflammation,
embolism and allergic reaction.
Treatment with doxycycline for 30 days to kill the Wolbachia parasite weakens the heartworms and makes them unable to reproduce, and greatly
reduces the chance of adverse reaction during heartworm treatment.


The Evolution of the Cell

There is compelling evidence that mitochondria and chloroplasts were once primitive bacterial cells. This evidence is described in the endosymbiotic theory. How did this theory get its name? Symbiosis occurs when two different species benefit from living and working together. When one organism actually lives inside the other it's called endosymbiosis. The endosymbiotic theory describes how a large host cell and ingested bacteria could easily become dependent on one another for survival, resulting in a permanent relationship. Over millions of years of evolution, mitochondria and chloroplasts have become more specialized and today they cannot live outside the cell.


As the Wolbachia is a living, thriving, inseparable part of the Heartworm, if one hurts/kills it, one is damaging the Heartworm itself.

I am aware of what the Doxy is for and also the concurrent use of Heartgard and told Gail about it in PM when she had PMd me with an inquiry. It is nothing new in terms of hw treatment. The main action of Doxy is to kill the Wolbachia. period If there is a side effect on the worms, it is just that...side effect. It is not curing the hw postive dog. Doxy is not capable of that.
Bottom line....immiticide is still needed or the adult worms live on and are hazardous to a pup. There are many people who subscribe to the "slow kill" as described earlier and I think it should be used in only extreme cases.
Rescuers are taking hw positive dogs and doing it and it makes me sick. if they cannot afford the appropriate treatment, they should save the dogs that are negative and leave the positive ones to rescues who will go the extra mile.
You all know how I feel about people who short cut treatment for their pups. People really need to rethink what they do in terms of preventatives as a lot of pups could be saved from the ill effects of HW treatment for only a few bucks/month and no side effects as some want to think.
I know what I know and will treat my pups accordingly and on the advice of veterinarians...not people on the internet. As for heartworm treatment, I have cared for many pups with heartworms in my time with rescue. It breaks my heart every time I have one because it is preventable. What they go through is very sad. Anyway.......This is not what the thread was for and I am as guilty as anyone for taking it off topic; and I will not be back.
Prayers for Zoey. I really hope she does well with her treatment, Gail! :)