Why do vets require dogs have a heartworm test before giving them preventative heartworm meds?

Question

OK- So, about 9 months ago my vet asked me if I wanted to get my dog tested for hw and put her on hw meds. I couldn't afford it so I said no. The vet tech took me aside and told me that the test was a scam, but she ended up testing my dog anyway for free.

Now I have another dog and I am in the same situation. I have a friend who knows a lot about dogs and thinks it is a scam too. What is the point of the test? Is it true or just a rumor that if they have heartworm and go on the meds that they will die? What are the chances of that? What are the risks???? Side effects??? Is it true that the preventative med and the treatment for heartworm is the SAME? Thanks!!!!

Answer 1

Heartworm Treatment

Treatment of Infection

It has been said that the treatment of heartworm infection is somewhat of an art. There are several strategies that can be used including the option of not treating at all. The important concept to realize is that very harsh arsenic based drugs are necessary to kill adult heartworms and that treating for heartworm infection is neither simple nor safe in itself. Let us review some of the dangers and options in clearing the body of this parasite.

Patient Evaluation

Prior to therapy, the heartworm patient is assessed and rated for risk into one of four categories. Important factors include: how many worms are thought to be present based upon the tests performed, the size of the dog, the age of the dog, concurrent health factors, severity of heart disease, and the degree to which exercise can be restricted in the recovery period. Some hospitals use computerized formulas to categorize heartworm infected patients. The categories into which patients are grouped are as follows:

• Class I: Lowest Risk. Young healthy dogs with minimal or no disease evident on radiographs, normal blood work, and no symptoms of illness. They may cough only occasionally if ever, they only fatigue with exercise, and their chest radiographs are normal.
• Class II: Moderately Affected. Healthy dogs with minimal signs as above, occasional coughing, fatigue only with exercise but with radiographs that show definite evidence of heart disease. Lab testing shows mild anemia, urine dipsticks show some protein present but not severe urinary protein loss.
• Class III: Severely Affected. Dog is suffering from weight loss, cough, difficulty breathing, blatant damage to the vasculature is apparent on radiographs, lab work reveals a more severe anemia and marked urinary protein loss.
• Class IV: Caval Syndrome. Dog is collapsing in shock with dark brown urine evident. Heartworms visible by ultrasound in the AV valve of the right side of the heart, very abnormal blood work. These dogs are dying and can only be saved by the physical removal of adult heartworms via an incision through the jugular vein. If such a dog can be saved from this crisis, further heartworm infection treatment cannot be contemplated until the dog is stable enough to fit into one of the other categories above.

After knowing what class the patient fits in, treatment can be determined. The dog has three groups of heartworms in his or her body:

• The microfilaria that are the newborn children of the adult worms living in the heart and pulmonary arteries. The microfilaria are swimming freely in the bloodstream, possibly in large numbers, and it is the microfilaria that can (through a mosquito) spread to other dogs. The microfilaria are killed so as to keep the dog from spreading the disease.
• The new arrival heartworm larvae, delivered from mosquito bites in the last 6 to 7 months. These are L3 and L4 larvae living in the skin (having arrived within the last 3 months). These will continue their maturation and repopulate the heart and pulmonary arteries if they are not killed before the adult worms.
• The L5 larvae and adult worms living inside the heart and pulmonary arteries. This group requires the arsenic compounds for destruction while the other two groups can be killed with less toxic products.

Killing the Microfilaria and Migrating Worms

Happily the microfilaria, L3, and L4 larvae can all be killed by monthly heartworm preventive products (i.e. Heartgard, Interceptor etc.). This step is done before killing the adult worms so as to quickly make the patient noncontagious and to see that there are as few worms as possible present when it comes time to kill the adult worms. We want as few adult worms as possible as targets for our adulticide therapy because adult heartworms are very large and their death is quite inflammatory. Embolism and anaphylactic shock are important risks. Fewer worm dead bodies mean fewer risks.

The problem with giving heartworm preventive to a heartworm positive dog results from the sudden death of large numbers of microfilaria. All those little worms dying at once create inflammation, possibly enough to cause anaphylactic shock. DEC (Filaribits) cannot ever be used in a heartworm positive dog. Other preventives, such as the ivermectin derivatives and milbemycin, kill the microfilaria more slowly and reduce the chance of reaction. That said, while most heartworm positive dogs get away with taking one of these products safely, ideally the dog should be pretreated with anti-inflammatory medication and observed in the hospital for this first day of treatment.

After this crucial period is over, the heartworm preventive is given normally (monthly) for several months before addressing the adult worms. How long one chooses to wait depends on how urgent the dog’s need is to remove the adult worms. After all, it is the adult worms that cause heartworm disease, not the immature worms addressed by the preventives.

Killing the Adult Worms

The only product currently available for the treatment of adult heartworms is melarsomine dihydrochloride (Immiticide made by Merial). If one goes by the manufacturers’ recommendations, treatment can be done in two doses or three doses depending on the class of heartworm infection. Most universities, however, opt to treat all patients with the three-dose protocol as it creates a more gradual kill of the adult worms (which is safer in terms of embolism and shock).

The patient receives an intramuscular injection deep in the epaxial (lower back) muscles. This is a painful injection with a painful substance and it is common for the patient to be very sore afterwards at home. Pain medication may be needed. Be very careful of the injection site as the pet may bite if you touch it. The site may actually form an abscess that requires warm compresses. Approximately 30% of dogs experience some sort of injection site reaction which resolves in 1 to 4 weeks. Some dogs develop a permanent firm lump at the site of the injection.

In the two dose protocol, the dog comes back for a second injection the next day on the opposite side of the lower back. In the three dose protocol, the dog comes back one month later for two doses 24 hours apart (the first dose representing an introductory treatment to kill some of the more sensitive worms.) Keep in mind, too many worms dying at once creates circulatory shock.

After treatment, the patient must be strictly confined for one month following the final treatment. No walks, no running around. The dog must live the indoor life. The reason for this is that embolism to some degree is inevitable and it is important to minimize embolism-related problems.

Watch for:

• Coughing
• Fever
• Nose bleeds

If any of these occur, report them to the vet as soon as possible. The most critical time is 7 to 10 days following a melarsomine treatment but they can occur anything in the following month.

Answer 2

I work in rescue and ALL dogs should be Heartworm Tested.I personally go with every two years if there's been no lapse in the preventative being given every month for those two years.Many vets are leaning towards every year because they use a 3 part test that also tests for lyme disease.Yes,It is true about if you give HW meds to a heartworm positive dog that yes,It could die.You really need to research this b/c the cost of treating a hw positive dog is far greater than the prevention.

Answer 3

Heartworm Meds

Answer 4

Heartworm disease in NOT a scam. I have seen several dogs die of this parasite. Heartworm is a parasite carried by mosquitoes. When the immature form enters the blood stream it needs 6 months to reach adulthood and reproduce. This is why puppy do not need to be tested. Adult dogs must be tested because if there is a large amount of immature heartworm (microfiliria) in the bloodstream, preventive can cause a severe reaction including death. This is because the preventive kills the immature form. Imagine a lot of tiny clots affecting the lungs and heart at the same time and you can picture this reaction. The prevention is only part of the treatment if a dog is heartworm positive. The adults must be killed first and then the immature form is slowly killed off over a several months. Please believe your vet...no one is in the profession to make money it is all about care of the animal!

Answer 5

Heartworm Test

Answer 6

Your vet tech is an idiot.

The testing is not a scam. The medication is expensive and will do zero if the dog is already infected. You in essence are wasting good money giving the preventative medication to an infected dog. The test rules out whether the dog is infected or not. If not, you use the preventative medicine. If infected, a totally different treatment is required to save the dog's life.

That vet tech is an idiot because it is not a scam. Heart worm is an actual worm that looks like a piece of spaghetti that works its way in and out of the dogs heart in various locations. All the holes it creates in doing so allows blood to flow outside the dogs heart and makes the heart stop working efficiently. The cure is a form of cyanide to kill the worm. If the worm has grown too large, the cure can kill the dog. This is why early testing when the dog is a pup and keeping up the preventative medicine is so important.

I would report such a stupid vet tech to the vet. She deserves to be fired.

Answer 7

The heart worm test is not a scam. It is a very important test for the diagnosis of heart worms in your pet. If you give your dog heartworm preventative w/o first testing and your dog is positive for heart worms then you could make him/her very sick by giving him the meds! The test is a safe measure before admisinstering the meds. Get your dog tested and then get your dog on some preventative. I rescued a Cocker that was 11 months old and had never been on any treatment and it cost me alomst $500 to get rid of the heartworms! Good Luck

Answer 8

Because if you give a dog with heartworms meds, the worms might not die, but a dog can still live a full life even through it has heartworms, that's what the vet told me anyways and another one said that he would die within a year. And that was about 4 years ago and he's still alive and his self.

Answer 9

yea if you dog has hw and takes the prev meds then your dog will die and also, yes, the test is also a scam.... a 100% big fat stupid scam

why would i say it's a scam? because you get a 6-8 pack of hw prevention meds. you don't take your dog back in 6-8 times to get your fluffy little friend tested every single time do you? of course not... so why does it makes sense for them to insist on getting your dog tested beyond the first time when he/she's already on the medication when there's no risk? there isn't any. it's a shameless money grab.

almost every vet i've met is no better than a shady mechanic using guilt and plucking on your heartstrings to squeeze $$ out of you.

on top of that, most of the medicine they say "if you love your dog, you'd do this" is actually adverse to their health... the risk doesn't outweigh the rewards.

scammy scam scammed

Answer 10

a) there is an increased risk of reaction to the medication if the dog/cat has heartworm

b) it works on the heartworm larvae that are less than 30 days old


some newer treatments lessen the risk of reaction or even eliminate it so that is becoming less of an issue, however treating a pet with an adult heartworm infestation with a med designed to limit the larvae from incubating properly will end up with a very sick animal

Answer 11

If you leave your dog outside a lot,then put them on meds. It stops Hw before they can hurt you dog. The point of the test is to see if your dog has Hw. I was told that treatments are 2 different things. Once your dog gets Hw it will always have it. The worms weaken the heart and can kill the dog.