Heartworm disease is a serious and potentially fatal disease in dogs.  It is caused by a parasite called Dirofilaria immitus.  These worms live in the heart and adjacent blood vessels of infected dogs.  The disease is transmitted by mosquitos.  In Texas, ALL dogs (even those that spend all their time indoors) need to be on heartworm preventive YEAR-ROUND.   Do not stop giving preventive in the winter months.  Dogs need to be put on preventive for the rest of their lives.  We recommend yearly heartworm checks so that if a dog is found to be infected, we can treat the heartworms before they cause damage to the heart and other internal organs.  The most common clinical sign of heartworm disease usually is no sign at all.  Other signs include chronic coughing, tiring easily, unwillingness to exercise, difficulty breathing, lethargy, and enlarging abdomen.  Dogs who have heartworms should not be put on heartworm preventive unless you have talked to a veterinarian first.  Prevention is safer and less costly than treatment.

The medication (Immiticide) used in heartworm treatment today is much safer than the medication used in the past.  For past treatments we had to give four intravenous injections of an arsenic based compound named Caparsolate.  The new treatment involves two injections in the lumbar back muscles 24 hours apart.  This will slowly kill the adult heartworms over the next month.

To make this procedure as safe as possible, blood testing and chest x-rays are performed to make sure that your pet does not have any underlying health problems.  The blood work is to make sure that the liver and kidneys are in the best possible shape (to metabolize the drug given) and that there is no hidden infection.  The chest x-rays are not to see how large the heart is.  Many dogs will have an enlarged heart because of the heartworms.  This enlargement will not significantly improve after the treatment.  The x-rays are to see if there is any inflammation in the lungs.  If the lungs are severely compromised and the pet is treated for heartworms, the extra burden of the dying heartworms could potentially cause death.  This is because when the heartworms die, they will travel to the lungs where they will be absorbed back into the body.  This can cause a lot of inflammation and we do not want the lungs to be overwhelmed.  Just because lab work and x-rays are performed, that does not guarantee that your pet will have absolutely no trouble with the heartworm treatment.  Certain precautions still have to be taken.

If the lab work and x-rays show some underlying problems, then we will address those problems before beginning heartworm treatment.  If the lab work and x-rays look good, then the injections will be started.  Based on when the first injection is given, your pet will stay in the hospital for 2-3 days so that we can monitor his reaction to the treatment. 

After heartworm treatment, it will take about 4 weeks for the adult heartworms to die.  This treatment does not affect any immature heartworms.  The immature heartworms will slowly be killed by giving the Heartgard® heartworm prevention monthly.  In the past, other mecications were used to kill these immature heartworms, but here at Claws & Paws Veterinary Hospital we feel the safest method is the slow kill with the Heartgard®.  During the next 4-6 weeks, it is very important that your pet’s exercise be severely restricted.  As the adult worms are dying, they will migrate to the lungs where they will be absorbed back into the body.  What we do not want is for your pet to do running and jumping where the blood starts flowing rapidly and a lot of worms migrate to the lungs at once.  We recommend a recheck examination on your pet 2 weeks after the treatment so that the Doctor may listen to the heart and the lungs.

After treatment your pet needs to be closely monitored for any changes in appetite, vomiting, diarrhea, back pain, lethargy/depression, and especially coughing.  Coughing is a sign that there is inflammation in the lungs.  Should your dog start coughing, we would like to see your pet that day.

The immiticide treatment is 98% effective.  Out of all the dogs treated over the past several years, there has been only one dog that needed a second treatment.  As far as safety is concerned, it is much safer to treat your pet for the heartworms than not to treat it.  Treatment also will not prevent re-infection.  After heartworm treatment your pet will need to be put on the prevention and kept on it.  If your pet misses a month later on, he could get heartworms again.

The quote that you have been given for the cost of the heartworm treatment includes the lab work and x-rays, cost of the immiticide, and hospital care.  Any follow up examinations done here at our hospital for the next month related to problems from the heartworm treatment are also included in the estimate.  Not included is the 6 month follow up occult heartworm test;  any treatment or extra lab work/x-rays needed before treatment can be started;   the heartworm prevention to go home following treatment;  any needed medications due to complications;  and if a second heartworm treatment is needed.

The safety of your pet is our primary concern.  Please do not hesitate to call our hospital should you have any concerns or questions.

Note: This article is provided by Claws & Paws Veterinary Hospital® for informational purposes only.