Heartworm Preventatives

Posted by Aaron

Thursday, June 18, 2009

Now that I've talked about heartworm disease, here's the skinny on heartworm preventatives:

You now know that mosquitoes are the carrier for heartworm. Exposure to mosquitoes is therefore required. Risk is highest for dogs outdoors at the hours of dusk and dawn when the little buggars are out feeding.


Mosquitoes come indoors! Dogs go out to pee or at the very least poo (usually). Although your risk is lower as an indoor only cat - about 1 in 4 SICK cats are considered 100% indoor by their owner. There is no such thing as a dog that doesn't need preventative.

Preventatives are critical. One common misconception is that heartworm preventatives work for the NEXT month after they are given. What's happening is that the preventatives are killing off any larva that the pet has been infected with over the LAST month. In other words, we assume that the pet has been infected and the preventative is killing them before they grow to adults.

There are many different heartworm preventatives out there. They all do the same thing - they kill the larva. All of the preventatives you should be able to get today are in the same class of drugs. Some people are still using Filaribits (DEC) but if you are - STOP. Some preventatives have activities against other parasites - some kill intestinal parasites or fleas in addition to heartworm larvae.

Common products you'll find are:

  • Heartguard (plus)
  • Interceptor (or Sentinel)
  • Advantage Multi
  • Revolution
  • Iverheart (plus)

They each have really pretty literature that shows how they are the best product on the market and all of their competition sucks. The truth is somewhere in the middle. They all have their ups and downs. Go with your veterinarian's recommendation. I'm a Heartguard man. Always have been. Always will be. All of these products are effective. All of these companies support their product claims. It's really a matter of your situation, what you think is easiest, and what your veterinarian recommends for your area.

The most important concept is that they are all intended to be given once a month. You have to use them once a month. The one exception out there is ProHeart. This is an injectable heartworm preventative that is given every 6 months.