Heartworms are large parasites that live in the arteries of the heart.  Their presence obstructs blood flow through the heart, resulting in heart failure.  The immature heartworm is microscopic and circulates in the blood throughout the body.  Mosquitoes transfer the immature heartworm from dog to dog via their bite in much the same way that malaria is transmitted.

Prevention

During Mosquito season dogs should be put on medicine to kill the immature heartworm before it has a chance to mature in the heart.  In Kentucky, our winters are mild, and we get warm spells during which the mosquitoes will come out of dormancy.  Therefore, we recommend keeping your dog & cat on preventive medicine all year.  Cats that go outdoors should also be placed on preventative!

The preventive medicine for cats & dogs comes in two forms:
Monthly chewable or a table form – These products are packaged with a supply of stickers for marking your calendar to remind you when to give it.  Monthly preventative is made with broad weight ranges, so it is easier to dose large, fast growing puppies.
Monthly topical spot on – Revolution is a spot on that is effective preventative against heartworms as well as fleas and some other parasites. 

Testing

Dogs should be tested yearly, even when kept on prevention all year.  Nothing is 100% effective!  Puppies 6 months or older must test negative prior to starting the preventive medicine.  A fatal reaction is possible if some types of prevention are started in a heartworm positive dog.

Cats have lower worm burdens than dogs making testing hard.  For them we recommend that they be placed on the preventative without being tested first.  There is not one definitive test and for them, the preventative medication is the treatment in a positive cat!  

Treatment

Heartworms can be treated by giving the dog atoxic compound to kill the heartworms.  This medication can also be dangerous to the dog. This treatment usually requires hospitalization, and it can be costly.  Some dogs may not be able to tolerate the treatment at all; it is much safer and less expensive to prevent the infection.

Click here for printable version. (PDF)

< BACK TO LEARNING CENTER