Problems with Heartworm Treatment

The perfect treatment for a disease needs to satisfy several requirements:  the treatment should be 100% effective and it should be completely safe for the patient.  If it were also easy to do, and inexpensive, that would be perfect.  When the standard treatment for a disease fails to satisfy all four of those requirements, people begin to look for alternatives.  Sometimes this results in better treatments.  Sometimes it results in the patient receiving no effective treatment because he's busy getting some quack remedy that does nothing at all (or kills him.  Remember Laetrile?).

Treating a dog to clear him of heartworms is a situation where the state of the art is not perfect.  Prevention of the disease with monthly preventive medicine has been effective most of the time.  Treating the dog who has adult, foot-long worms in his heart -- that's a different story.

The conventional view is that the worms are in the right ventricle of the heart, and the big pulmonary artery trunk.  If you do a post-mortem on a dog who has died from heartworms, you'll find a lot of them there.  In a dog with a lower worm burden, there are not so many worms in the heart.

Most of the worms will actually be in the pulmonary arteries (taking blood from the right side of the heart to the lungs to get oxygen).  There may not be any worms in the heart.  If you open this dog at post-mortem, even though there may not be huge numbers of worms, you can cut the lung way out at the edge and find worms in the blood vessels.

The worms don't eat the heart or arteries, they just float.  When there are so many worms present that they clog the outflow from the heart (like roots in a pipe), the heart wears out (prematurely) from the constant overwork of pushing blood through the clog. 

Actually the worms don't just float -- they swim upstream. If they just floated, the pressure in the artery would force them downstream until they hit a branch too small to pass.  This would clog the artery either partially or completely, resulting in poor circulation to the downstream area of lung.  The dog might get a secondary pneumonia in this damaged area.  If he ran hard, increasing heart rate and blood pressure, the damaged artery could blow out, hemorrhaging into the lungs.  Indeed this does happen in some dogs, though most infected dogs develop the less dramatic signs of congestive heart failure: weight loss, coughing (especially after exercise), labored breathing, fainting spells and so forth.

This is ALWAYS what happens when the dog is treated to kill the heartworms.  Worms who have been swimming upstream, keeping the artery open, float downstream and clog up the works.  Unlike an intestinal worm infection (hookworms, roundworms, tapeworms, etc.), there's no exit here.  With intestinal worms, you kill the worms and they leave the body with the next bowel movement.  With heartworms, they clog up the works like a blood clot would (except that few blood clots are a foot long).  You've heard that you shouldn't get an air-bubble injected -- how about a handful of foot-long worms?  The only way to get rid of them is to let the body's microscopic white blood cell defenders eat them.  They'll do it, but it's a slow process, like termites eating your house.  It takes weeks after the death of the worms before the body dissolves them out of the circulation and opens all those clogs.

This is the unsatisfactory part of the heartworm treatment.  It's why dogs feel bad a week or so after they are treated.  That's when the worms die and shift position.  The dog may have a fever, cough, lose appetite, have trouble breathing, or cough up blood.  Sometimes you don't see any of those things, but you can just tell that your dog doesn't feel good.  You know your dog, and even though he may not have specific signs, you can tell when he doesn't feel well.  This is the reason we ask you to restrict the dog's activity for several weeks after treatment -- no hard running for a while.

Most complications of treatment are minor and very treatable.  Severe problems like blood-vessel  rupture or allergic-shock-like reactions are extremely rare.  It could happen, but most dogs have years added to their lifespan when the heartworms are destroyed.

Here's the crux of the matter, and the reason I'm writing today.  Ill effects during the heartworm treatment are related almost exclusively to the dead worms clogging up the pulmonary arteries.  The drug that's used (Immiticide TM - melarsomine dihydrochloride) is unlikely to cause anything worse than some temporary soreness at the injection site.  It takes those little worms five days to die and they're taking a  bath in it.  There just isn't enough drug to bother the dog (unless he has some pre-existing severe liver disease).  That's why it doesn't matter whether your alternative remedy is a better chemical, a cheaper chemical, organic, holistic, homeopathic, herbal or black magic.  If it kills the worms, the arterial blood pressure is going to shoot them downstream and clog up the works.   

I've seen people use D-con rat poison, gunpowder, and levamisole (a sheep-wormer that is VERY hard on the dog's liver).  Today a client brought in some misinformation he'd downloaded from some "Natural" website (with many products for sale).  Their nostrum is alleged to be superior because "There seems to be no risks of the parasites dislodging and creating vessel blockage."  Yeah?  Do the worms die or don't they?  If they die, they're going to move.  You may not have seen an artery pumping, but a two-millimeter artery will shoot three feet in the air if your clamp slips off before you get it tied.  Dead worms don't swim - they go scooting downstream.

I wish that our standard heartworm treatment was 100% effective, safe, easy and inexpensive.  It doesn't totally satisfy any of those criteria.  It is usually effective in eliminating all the worms, most dogs have no complications (or very minor and easily treatable ones), and it just takes two injections, 24 hours apart.  But, it's not cheap.  And you have to let the body deal with those dead worms.  There's just no way around that, no matter how you kill them.

P.S. Don't forget to give your dog his heartworm preventive.

Comments

[Doc]

Hello, Lynn,

There are some specialists who feel that heartworm positive dogs are more likely to experience ill effects with Interceptor than with Heartgard (a different drug).

I personally have not seen reactions with it, but some people have, and this may be part of your problem.

The Snap Test is pretty specific, in that it is unlikely to react to things other than the protein from the adult female heartworm reproductive tract.

Sensitivity refers to how many worms you would have to have present in order for the test to pick it up. This type of test (Snap, Abaxis, Witness, other "chair-side" tests) can give false negatives if fewer than four adult female worms are present.

A second Snap test may not tell you what you want to know. If positive and there WERE some type of cross-reaction (non-specific) , it might be the same thing. If negative, it might mean that you just have very few worms and were lucky to find them the first time.

In a case where there is uncertainty in our own lab, we always send a new sample out to an outside reference lab, like Antech.

If there are very few heartworms, most dogs have disease only in the pulmonary arteries, not in the heart. However, there is no good way to count the worms unless the dog dies and you cut him open.

If there are very few or no worms present, then the enlarged heart is probably due to something else, and could be worked up separately. An echocardiogram (ultrasound exam) can give you better information about the heart function than just an X-ray and physical exam.

Since I have not seen your dog or its circumstances, I can only give general information. You really need to discuss this with your veterinarian.

Best wishes.

[Holly]

Hi. I am confused about treatment for a very small rescued Brussels Griffon who is heartworm positive. She is young but very lethargic. The x-rays show a somewhat enlarged heart and pulmonary edema so my vet wants to use Immiticide. We are doing a month of doxy along with lasix and enalapril in the meantime. The rescue vet (without doing bloodwork or x-rays) says she's too small for the shots and should do doxy and Heartguard only because of her size (6.5 lbs.)

Does a small size increase a dog's risk? I'm obviously very concerned about making the wrong decision here. It didn't take this little girl long to be a very important part of our family. Thanks for any information.

[Doc]

Hello, Holly,

Very small dogs don't have much room for the dead heartworms to occupy. Three worms takes up a lot more of their pulmonary artery space than three worms in a German Shepherd Dog. They are indeed more likely to suffer complications from the breakup of the dead worms.

HOWEVER, they are also more likely to suffer illness with a small number of worms, for the same reason. Thus, I feel they should be treated.

The problem with just leaving the dog on Heartgard is that eventually, the heartworms present will die of old age. When this happens, the complications will be similar to those that would occur if you killed them with the treatment.

The difference is, with the treatment, you are doing everything possible to minimize the complications, and you also know when they will occur. Thus you can be watching the dog more closely and restricting its activity during this time.

You can't do that for the rest of the dog's life.

It sounds to me like your veterinarian is proceeding appropriately. I cannot give specific advice, as I have not seen your dog.

Discuss your concerns with your veterinarian.

Good luck.

[Beth]

Thank you so much for putting this info up.

Today I just found out that my dog Jewel (a German Shepard/Pit Bull mix) has heart worms. This has come as a hard blow for me.

To make a long story short: she is 3 years old, we got her as a puppy and have always had her on prevention until last year sometime (got busy). It tears my heart to know that it is my fault.

I don't want her to go through the pain, and knowing that other problems could come up makes me feel even worse. Also, she isn't too active, but every time she sees me she gets very exited (jumping around and everything). She is an all-the-time-outside-dog, so I can't watch her 24/7. But the main thing is, we can't pay for the treatment, and/or the other things that would happen. I am so sick over this and have cried for hours.
Would be be worth it to get a second opinion? (we have been going to this vet hospital for years, though it was a different vet) or should we really consider putting her down? I know that that isn't the best option, but at the moment I can't see any other way to keep her from being in pain.

[Doc]

Hello, Beth,

Not having seen your dog, it's hard for me to give you specific advice.

We have several patients whose owners are not able to do the treatment right away. We put those patients on Heartgard. This will keep them from getting many more heartworms, and is unlikely to cause a problem. At least you are "holding the line".

While it would be better to clear the dog, I wouldn't have problems with holding the line until you are able to. If the dog feels okay, I cannot see any reason to euthanize at this point.

We treat plenty of dogs who are outside while their owners go to work. Certainly 24-hour observation would be ideal, but it is almost never the case.

It sounds like there is some failure to communicate here, either from the veterinarian to you, or from you to me.

Please contact your veterinary hospital and ask to see your regular doctor. Share your concerns with him/her.

Best wishes.

[Barb]

This is a great site. Helps to know that others are going through this. We adopted a male lab in January this year. When we took him to the vet, we found out that not only did he test HW+, but his previous owner knew that he tested HW+ in June 2009 and did nothing. Maddening.

Here's our update: we treated the 4 weeks of doxycycline to kill the wolfbachia. We also did a shot of invermectin. We did the first immiticide shot in February. Rather than do the 2nd/3rd shots after 30 days, our vet chose to wait at least 3 months. We used monthly Heartguard in between the treatments.

Her line of thinking is that since the first Immiticide shot only kills adults, and the Heartguard only kills the microfalria, then we waited 3-4 months for any surviving baby heartworms to grow into adulthood. That way, all worms would be killed at all stages. Any worms that survived the 1st shot and made it to adulthood would be killed with the 2nd and 3rd shots.

Have you heard of this process before? The vet was at a conference the week before my appointment, and said that this was presented. It does stretch out the healing process, but seems to possibly have a higher percentage kill rate.

Anyway, we had shot #2 yesterday, and #3 this morning. I am just hoping and praying that we'll get through the next critical time period as the worms die off.

Any thoughts on this new 3-4 month approach? It makes sense to me, even if it does take more time.

[lynn]

Is doxycycline use recommended for dogs in all stages of heartworm? Is it now standard protocol to use this? My vet is not using it, and I'm just wondering in what situations it's not indicated.

[Doc]

The use of doxycycline is widespread. Is it the standard of care? I don't know that I could say that. It is recommended by the heartworm society researchers.

While some dogs do not tolerate it, having nausea and so forth, most do well with it. It inhibits the Wohlbachia micro-organism which is beneficial to the heartworm. This causes the heartworms to become weaker (and more easily killed), and smaller (less to dissolve afterward).

That being said, we treated thousands of dogs without it until the research recommending it was done.

In most cases, I believe that it cannot hurt and that it probably helps a little. I haven't done any controlled research, so I rely on those who have.

Thanks for reading and writing.

[Doc]

Hello, Barb,

The delay of three to four months would be important based on what time of year the dog is being treated. If you are already six months past the peak mosquito season, then everything that is going to develop is already developed.

In my area, that peak is July and August. If I diagnose and start treatment in January, there is little use in waiting three months for the next treatment.

If I am treating in September, then I certainly would finish treatment in January.

It is a function of when the dog's unprotected exposure to mosquitoes has taken place, and the time of year that treatment has begun.

Clear as mud?

[lynn]

I read about people using the terms "weak positive" antigen test result or "strong positive" antigen result. Could you explain what that means? Does it have any bearing on diagnostic plan or treatment plan?

Thanks.

[Doc]

Theoretically, that would indicate smaller or larger worm burdens.

In my opinion (and that of some bona fide experts, which I'm not), this is a qualitative test. Positive means yes, negative means no (or less than four adult female worms - false negative results can occur when worm burdens are this low).

I do not feel that you can make a meaningful determination of the number of worms from how "strong" the test result is. It's a color change, like a pregnancy test. "How pregnant are you?"

I make my estimate of worm burden based on the number of unprotected months of mosquito exposure, age of the dog, and whether there are any outward clinical signs of disease (as opposed to just a blood test result).

Chest X-rays will show changes in the pulmonary arteries, lungs and heart size.

For what it's worth, my opinion is that the usefulness of the blood test is just "yes or no".

If it turns up "yes" when I don't think it should, then we draw another blood sample and send it out to an outside reference lab to double-check.

Thanks for reading and writing.

[Jodi]

Our newly adopted pup (a German Shepherd-- approximately 2 years of age and 55 lbs) just completed her Heartworm treatment two weeks ago, the day before we adopted her.

She is not yet spayed (and delivered a litter at some point in her young life) and we're getting conflicting advice from two different veterinarians regarding when it is safe to spay her. Our vet is willing to spay her 6-8 weeks post treatment, the vet that the rescue uses (and administered her heartworm treatment) suggests waiting six months before spay.

I'd like to be conservative and ensure that all of the dead worms have cleared her system before subjecting her to surgery but I also don't want her to unnecessarily go into heat either (that said, our other two dogs are spayed females and she doesn't have access to any male dogs so pregnancy isn't an issue.)

Thank you for your website, it's been immeasurably helpful!

[Doc]

Hello, Jodi,

The physical bulk of the dead adult heartworms should be totally dissolved by 5 to 6 weeks post treatment.

Theoretically, this means that you have no more risk than a dog who never had heartworms by the time you get to the six-week mark.

However, there may be weakened pulmonary arteries as a result of the downstream movement of dead worms and partial blockages that result. These weakened areas are more susceptible to breaking and bleeding under stress.

This accounts for dogs who get the go-ahead for return to normal activity, and have a bleed when they start exercising again. This is rare, but it does happen occasionally (like, for me, 6 times in 30 years).

This would be more a factor in exercise than in anesthesia, in my opinion.

Six months sounds like an arbitrary figure, but if the dog isn't healed by then, it probably never will be.

At six weeks, you've just gotten rid of all the chunks of worm, so you could conceivably have some need to heal.

I have spayed heartworm positive dogs because there was a strong risk of unwanted pregnancy, which would be a mess in the situation they were in. If the dog seems healthy otherwise, I am okay with this. Of course, this is in a dog that I am actually seeing and examining (which I cannot do with yours).

You make a risk versus benefit decision with anything you do.

Since you can prevent exposure to the male, I'd have a tendency to wait at least till three months post treatment. My bias, based on experience, may be nothing more than my own prejudice. There's a lot of gray area here.

Good luck.

[lynn]

Can heartworm lead to hair loss? Or can the preventative Interceptor cause hair loss? Since he's recently adopted, I'm not sure what's typical shedding for my dog (Chow-Corgi) for this time of year. Near his hind quarters, his hair is coming out in chunks. He is otherwise showing no clinical signs.

[Janet Evans]

Dear Dr,
I am the very proud mother of the best dog in the world (sorry you other mothers...) named Riley who is a Lab Mix I got from the pound 7.5 years ago. He had a rocky start, getting an auto-immune disease when he was about a year old and went on/off prednisone a handful of times over the next few years, seeming to need smaller doses for less time during each flair-up. The vet seemed very sad that first episode and appeared to strongly be preparing me for the realization that Riley would be living a short and troubled life - but my priceless companion has been auto-immune-disease-free for about 4 years now (it went away? is that possible?) Plus he has a number of "lumps-and-bumps" now that the vet says are just fat-based fluid-filled sacks that come with age and are not-pretty but also not-harmful. The lump on his side is the size of a good grapefruit.
He went to the vet 2 months ago for poor exercise tolerance and she ran a barrage of blood tests (all good) and felt it was probably arthritis, giving him some nutritional supplements. He went again last night for the gradual onset of panting in addition to the exercise intolerance and she ran tests to find he is positive for HW. He is not coughing. We are awaiting the "confirmation test" that should be back in 10 days before starting treatment. She X-rayed him and saw "a good-sized round mass in-between his heart and his lungs which could be the worms or could also be a tumor." She saw it on one view but not on the other. He tested negative for HW 8 months ago (November) so, I assume with no mosquitoes in Ohio in the winter months, got this 3-4 months ago at the most.
You are truly an angel here on Earth for answering questions and I know God will find a place for you some day... A couple of questions that I have: Is it that "confirmation" lab test that is sent out that tells me what "Stage" Riley is in? Is it a good sign that he has not yet developed a cough? Do tumors and worms look alike on an X-ray? Does his health history complicate his ability to go through the usual HW protocol you describe so thoughtfully? Do you think my best friend can do this? It will break my heart to an extent I can't describe to lose him (I might die with him) but above all else I don't want him to suffer.
Bless you for your precious time.
Jan

[Doc]

Hello, Lynn,

I have not seen hair loss associated with either the heartworm disease or with the oral preventives. Sometimes there is a spot of hair loss where topical preventives are applied (such as Revolution or Advantage Multi).

I would be looking elsewhere for the cause of the hair loss.

Sorry about the late reply. I was out of the country for two weeks visiting my daughter who is a Peace Corps volunteer in Zambia. We had not seen her for 17 months.

[Doc]

Hello, Janet,

A really enlarged pulmonary artery trunk looks almost like a growth on the side of the heart base when you look at the X-ray from the ventro-dorsal view (dog lying on back, X-rayed from the underside of the chest). This is called "pulmonary knob" by some folks.

While it is possible that your previous heartworm test was a false negative (fewer than four worms can certainly be missed on the test), I would think that at least the dog wouldn't have had much of a worm burden. Thus, it seems very unlikely to me that a dog in that condition would develop a huge pulmonary artery in such a short period of time. This makes me very concerned that there is a mass of some kind in the chest.

The confirmation test is a more sensitive test for the presence of the adult heartworm protein. Commercial laboratories give us "quality control" when we don't believe our own results. It is basically just a "yes or no" test, though.

It would not tell you anything about the dog's health, other than whether or not heartworms are present. Small numbers of heartworms generally are quite well tolerated, causing no changes in the dog's health or appearance (incredibly enough).

In other words, if a dog with one heartworm is coughing, he is coughing for some other reason.

Dogs with a history of auto-immune disease can have a relapse triggered by any major illness or event. So it is theoretically possible that going through the heartworm treatment could do that. I really don't have specific experience or expertise in that particular situation.

I am certainly not able to make specific recommendations for your dog. Your veterinarian knows your dog and has seen the tests and X-rays, and is the best person to advise you.

That being said, your description does not put heartworms very high on my list as the cause of this dog's "ain't doing right" condition.

If nothing else turns up, you might ask your veterinarian about referral to an internal medicine specialist.

Good luck.

[lynn]

Thanks, Doc,

Another question: can the ingredient in Interceptor cause drowsiness or vomiting in some dogs? Just gave him month number 3 dose of Interceptor a few days ago and he seemed to get really drowsy, his eyes weren't as wide and bright; just didn't seem to feel good, he vomited 9 hours later. Last month's dose was given with Benadryl, which causes drowsiness anyway, this last dose was not given with Benadryl. He did have a reaction (vomiting, increased respiratory rate) 2 1/2 hours after his first dose (in hospital). The vet said this reaction happened earlier than in most dogs. I'm wondering if he could be sensitive to the ingredient and if it would be better to switch to another product, and what is the protocol for switching products?

[Doc]

Hello, Lynn,

There are some specialists who prefer not to give Interceptor to dogs who already have heartworms, particularly if they have circulating microfilariae (baby heartworms).

I have had numerous dogs who became positive while taking Interceptor, and I allowed them to keep taking it with no problems.

However, if there seems to be a problem every time you give it, I would ask your veterinarian about switching to Heartgard, at least temporarily. That seems to be less of a problem for dogs that have heartworms already (at least in some cases).

It would be worth a try.

Share your concerns with your veterinarian.

[lynn]

Thanks again for the info. I have shared my concerns with the vet; the vet would like to keep him on the Interceptor and monitor his reactions for now because of the resistance of the Heartgard. I didn't realize that the resistance issue was specific to Heartgard. Can you explain this? Because its been around longer? Used more? Does this seem to be the case all over or specific to the southern regions?

Another vet pointed out that the dogs hair loss was of no concern; just shedding his undercoat. Difficult to know what's normal with a very recent adoptee coinciding with very recent diagnosis.

I just got the dog back two days ago from injection 1. He seems to be doing well.

Awhile back you mentioned the importance of putting pressure on the injection site to avoid infection. A vet friend in Atlanta who sees far more cases than AZ, told me to make sure that the injection site gets shaved before administering the injection. He's seen some bad secondary infections from dogs who were not shaved at the site. I just wanted to pass that along for everyone else about to go through injections now or when the immiticide becomes available to you. My dog was shaved and the injection site looks great, no swelling or redness. He's on tramadol for pain, and is only exhibiting mild soreness.

[Doc]

Hello, Lynn,

In my practice I have seen about the same rate of failure percentage-wise with Heartgard, Interceptor, and Revolution. I had more dogs on Interceptor, so I had more failures with Interceptor. The percentage was the same.

[Carmel Hunt]

Hi. I have a 12 year old mixed breed who has been on Heartguard preventative most of his life. Unfortunately, he recently tested positive for heartworms. We live in the South, and he is an outside dog. Anyway, the vet said because of his age and the expense that we should just give him prednisone, doxcycline, and sentinel, and that he would eventually suffer from congestive heart failure. Will this regimen even help? What exactly will it do? What is the pattern of treatment? The vet mentioned to give him the prednisone alternating months. What do you recommend for the frequency of these meds?

[Gina Downs]

Had our cocker spaniel treated 5 hours ago with his first shot.
For the past 5 hours, he can not get comfortable, fidgets, lays in unusual positions.
When walking, his right rear leg is toeing-in and his walks clumsily, often positioning that right foot too far under his body.
In just the last hour, he has started some toe-dragging with that right foot. Not severe, and he corrects upon moving further into the stepping process.
Also, he has started to drool excessively. Both ears are wet as if he drank from a flat bowl.
Have given him 2.5 mg Diazepam to try to make him more comfortable.
Forgot to mention ... the vet had to stick him twice unsuccessfully and then changed needles and successfully administered on the third try.
Do you think he is just experiencing more pain than usual because of the three 'sticks' at the site, or should we be concerned that something else is going on?

[Doc]

Hello, Gina,

Please call your veterinarian and let him/her know what is happening.

The medicine in the treatment (Immiticide) can cause a lot of inflammation at the injection site. This can occur no matter how smoothly things go and how little it seems to bother the dog at the time.

This can range from being absolutely undetectable to a dog that is crying constantly with pain. Diazepam helps with anxiety, but has no pain relieving properties to speak of.

Please contact your veterinarian about this, as human 0ver-the-counter products can be harmful to your dog. However, it sounds very much like your dog needs pain medication.

The pain usually subsides in a couple of days, and most dogs don't have this type of reaction, but the ones that do get painful do need some help.

The difficulty in walking may indicate that the inflammation is causing enough swelling to put some pressure on a nerve root.

Call your veterinarian and report this situation.

Best wishes.

[Gina Downs]

Thank you so much.
We did call our vet and he said to give Ecotrin low dosage. We did and our cocker finally got comfortable.
This morning, he is walking fine and is almost as merry as usual.
Unfortunately, we have to have the second shot administered in another hour or so.
I want to choke the irresponsible owner who failed to give this fabulous dog heartworm preventative. In fact, ANY owner who doesn't take this disease seriously. Don't wait to see first hand how painful the 'cure' can be, you can't imagine the pathetic, helpless look your dog adopts when under this kind of stressful treatment.
GIVE THE PREVENTATIVE and GET SERIOUS about giving it according to protocol.

Thank you, doctor, for listening and giving valuable advice.

[April]

I have a 6 year old Golden Retriever mix that I adopted from a local animal shelter three years ago. They were a small, low budget operation and since he was already neutered when his previous owners surrendered him the shelter signed him over for free. He seemed very vibrant and healthy so we opted to use Southern Agriculture's walk in vaccination clinic to get his shots, but unfortunately did not get a comprehensive medical exam. The following year we scheduled Tanner for follow up shots and a full exam because his breathing had become noticeably quick and labored and he seemed to have trouble getting comfortable and would roam and switch locations several times before settling and going to sleep. He tested positive for heartworms, and his chest X-ray showed significant signs of infection. Dr. Poteet put him on Doxycycline and Heartguard, and Prednisone I think, and a few weeks later he started the Immiticide injections. Shortly after the final round of shots my husband and I went through a bankruptcy and divorced. I took Tanner with me when I relocated, and have just recently been in the financial position to start taking him to the local vet. It's been a little over a year and his recent bloodscreen tested negative for heartworms. She said everything looked good, but I am still concerned because his breathing is still fast and heavy, and he now gags and coughs, sometimes vomiting clear liquid. The only thing the vet found was a yeast/bacterial infection in his ear which has been treated and since gone away. Should I be concerned about the breathing and gagging? He just doesn't seem comfortable and I can hear him breathing from across the room. He will take several rapid breaths and then pause, wheeze as if he is straining, and then let out a heavy sigh before continuing with the same pattern. He also has excessive thirst. It's not unusual for me to fill his indoor bowl two to three times a night after I've gotten home from work. Are these symptoms normal after heartworm treatment, or are they totally unrelated? Any advice or insight would be greatly appreciated!

[Doc]

Hello, April,

Those are not normal findings after a heartworm treatment.

If I were seeing a dog with this description, I'd be doing a complete blood count, Biochemistry panel, and chest X-rays.

You should share your concerns with your veterinarian who is actually seeing your dog.

When they don't hear from you, they assume that things are going well.

Get in communication with your veterinarian and tell him/her that things are getting worse and that you are worried.

Good luck.

[Michael]

I have a 10 year old Siberian Husky who recently tested for mild/severe case of Heartworms. He's presently going through the treatment process (shots completed 15 days post now) and is feeling and eating better, but my question is regarding his leg. A couple days ago his leg grew to about double it's normal size and vet put him on furosemide for pitting edema. The vet stated that its a sign that his body is working hard to fight off the worms and it is a good and bad sign, is this true? How concerned should I be right now about his kidney failure. I understand his age is not on his side right now. We just moved to this town so trust in my vet is not at 100%. Thank you for your time!

[Doc]

Hello, Michael,

When heartworms die and break up, the pieces can block blood vessels. This is generally in the lungs. The inflammation involved in the process could certainly cause a blood clot to form somewhere else.

It is not common to see a leg swell after treatment.

I feel sure that your veterinarian is using a safe dose of furosemide (a diuretic, generic for Lasix), so I wouldn't be too worried about the kidneys on that account.

If the leg swelling does not go down rapidly, be sure to tell your veterinarian. Just because your dog has been treated for heartworms, this does not mean he cannot have other diseases.

Usually a big leg means a swollen lymph node that won't let fluid drain. It can also be an infection in the leg itself, or inflammation from some other cause.

Be sure to keep your veterinarian informed of your dog's progress.

Good luck.

[lynn]

My dog is 8-9 weeks post immiticide treatment. My vet had scheduled an 8 week check-up and I was told it was to be for a HW antigen test.

I moved to another state. Just had the dog tested at the new vet 8 weeks post immiticide treatment. The vet drew blood, came back about 10 min. later and said he was negative. Great!

Just got a call from the vet that although the test was negative, he went back and looked again afterward and he saw small traces of antigen and wants to test again and have it sent to a lab.

Can you guess how this may have happened? Can a Snap test change from negative to positive?

Is 8 weeks too soon to do a SNAP test? What is the recommended schedule for testing to see if the worms have cleared?

Should I be keeping the dog exercise restricted (no hiking with me)until he tests negative?

I don't use "blessing" very often, but your blog has been a blessing during this long ordeal.

Thank you for your time!

--Lynn

[Doc]

Hello, Lynn,

At 8 weeks post Immiticide treatment, we would not expect any physical chunks of worm to still be present. Thus, a gradual return to normal activity is what we usually recommend at this point.

Even though there are no "chunks" of worm left, there can still be heartworm protein (antigen) circulating in a dissolved form in the blood stream for four to six months after the Immiticide.(This is per Dr. Ron Blagburn, heartworm researcher at Auburn University).

We routinely test at four months post-Immiticide, but if the dog were still antigen positive at that point, I would test again two months later.

Bear in mind that the antigen test often gives false negative results if there are fewer than four adult female worms in the dog's body. It is possible to have a negative antigen test and still have a small number of worms that have escaped death in the treatment. This is unusual, but possible.

From your description of your situation, I would ask your veterinarian about delaying the follow-up test until four months post-Immiticide.

[Lara]

Is there anything you can give a dog post Immiticide to alliviate symptoms, more specifically the pain and coughing/gagging?

[Doc]

Hello, Lara,

We generally send our patients home with prednisone for the inflammation in the pulmonary arteries.

Most patients only have pain at the injection site for a couple of days, if at all (most dogs do not seem bothered, but some are very painful). We generally use tramadol for pain in these cases.

You should call your veterinarian and let them know you are having problems.

Good luck.

[Charles]

Hi Doc,
I have a 5 year old Rottweiler who has completed his heartworm treatment but is continuing to lose weight despite my increasing his food intake, I have already wormed him with Pancur. What else could be causing his weight loss? He was 105 before treatment now he weighs just 80.

[Doc]

Hello, Charles,

This is not expected with the heartworm treatment. The weight loss should be worked up as though the heartworm treatment had never happened.

If stool exams are negative (and the panacur was a good start), the next step for me would be screening bloodwork - CBC, chemistry panel, thyroid.

Nothing there, then imaging of the chest and abdomen.

I think it is very unlikely that this related to the heartworm treatment. Immiticide could be toxic to the liver, but that is a very rare event. The bloodwork would indicate liver damage.

Routine blood tests won't tell you about liver function. There are other tests for that, like bile acids. The liver assembles what you eat into a form that can be used or stored.

Weight loss is either:
1. no access to proper food
2. inability to digest food
3. inability to absorb nutrients from the gut into the bloodstream
4. inability to utilize the food (liver disease or diabetes, for instance)
5. nutrients being consumed by parasites
6. nutrients being consumed by fast-growing cancer cells
7. nutrients being lost via kidney or gut damage

You need to take this guy back to your veterinarian.

Good luck.

[Cindy]

My 14 1/2 yo flat coat retriever rescue was cured of heartworms about 12 years ago. I am curious as to whether this condition/treatment many years ago could have resulted in some damage and is a reason for his rapid breathing, at this senior age. We realize he is old, has arthritis and likely CUshings (I.e. almost constant panting). He is now on tramadol, about 1 wk on novifit so far. Blood test did not show any unusually high readings, negative for parasites in stool. No heart or other problems during examination. Due to his age and how stressed he gets when we see the vet we are reluctant to run too many tests, and would not want to put him on the drugs for cushings. He is due for an ultrasound in a couple of wks. It is difficult to tell if this almost constant rapid breathing (about 64 breaths a minute)even when sleeping is because he is in pain. His gums have always been a light pink. His appetite is good as well as his bodily functions. He does seem to tire easily on the way back from a walk and can get wobbly. He continues monthly iverhart max. We just want him to be as comfortable as possible, and seeing him decline is heartbreaking. We have the highest confidence in our vet. Could his heart or lungs be functioning at a diminished capacity because of heartworms at an early age?

[Doc]

Hello, Cindy,

I think this is unlikely to be a major component of your dog's problem. If he had suffered much heart and lung damage at the time, he probably wouldn't have survived to be 14&1/2 years old.

I understand your concern about stressing him with diagnostic procedures, but they may allow for a treatment that will improve his quality of life, if not actually extending it.

Just keep sharing your concerns and observations with your veterinarian.

Good luck, and thanks for reading and writing.

[A Facebook User]

Thank you for this blog and the concise, well-communicated information. Would you please help clarify my dog's situation for me? She appears to be a long-haired Chihuahua, adopted from the shelter on January 12. On January 4, the shelter listed her as HW positive based on the IDEXX test. They "aged" her at about six months and she weighs about 8.5 pounds; she was spayed January 9. She came home with five days worth of doxycycline.On January 13, we took her to our vet, who did a HW panel, which also came back positive. She had two views shot on January 19, which came back completely normal, and no microfilariae were detected. Also, the vet estimated her age at 8 months rather than six months. We continued the doxycycline for three weeks, then she got her first injection of Immiticide on February 3. We were told at that point that she would need her second injection in 30 days, and no continued doxycycline. however, I see that you mention two injections in 24 hours as standard protocol. On top of all this, my father died on January 15, and I've been preoccupied with all that entails, and now I'm confused about the right treatment for Josie, not to mention the challenge of keeping a very friendly, very happy, apparently otherwise very healthy young dog quiet! Oh, and congratulations on your daughter's Peace Corps work - very impressive.

[Doc]

Hello, Facebook User,

Since heartworms take six months to develop to a detectable stage, we know that your dog is older than six months (though we don't know how much older).

The normal appearing chest X-rays and the very young age of the dog mean we are probably dealing with very few worms. This makes the prognosis pretty good.

Very small dogs can have problems with very small numbers of worms, simply because they don't have much room for the worms to get clogged up in. Two worms in a tiny dog take up a lot more of the pulmonary artery volume than ten worms in a huge dog.

The effect of the four weeks of doxycycline can last for up to 3 months, so that's why you aren't taking it again.

I suspect that if you simply ask your veterinarian about it, they really are planning to do two injections when you return. I suspect this is just a little glitch in communication, as it sounds as though your doctor is doing a great job for you.

Always ask your veterinarian when you have questions. We are often so sure that we are great communicators, and don't realize we have not fully succeeded in that area.

We would much rather you'd keep asking until you are satisfied that you understand the answers.

As far as keeping the dog quiet, we just try not to encourage any strenuous exercise. It is not desirable to keep the dog in a cage for two months.

The exception would be a dog who is having noticeable complications, and then we often do confine them to cage rest until those complications resolve.

Thanks for the kudos to my daughter. She is happy in her work, and that makes me feel like a parent who didn't screw up too badly.

Thanks for reading and writing. Don't forget to call your veterinarian with your questions.

[karen brown]

I was wondering if the worms inside the heart produce more babys. Or if the larvae only comes in through the blood stream via a misquito bite??

[Doc]

Hello, Karen,

Oddly enough, the answer to both of your questions is YES.

The adults in the heart do produce babies that circulate in the bloodstream (microfilariae).

These babies are like Peter Pan - they never grow up.

Babies that are sucked out of the dog by a mosquito undergo a change inside the mosquito. Then they ARE capable of growing up when the mosquito transmits them to another dog (or even back to the same dog).

I couldn't take blood from an infected dog and infect another dog, no matter how many babies were in the blood. The mosquito is not only a carrier, but an essential part of the parasite's life cycle.

Thanks for reading and writing.