Understanding Heartworms

With mosquito season upon us, it’s time to think about heartworm disease. Transmitted through mosquito bites, this is a serious parasitic disease that can do major damage to your pet’s heart and other internal organs. Most veterinarians now recommend that you administer heartworm preventatives all year long. However, these toxic medications aren’t benign and, scientifically, they are not necessary for more than a few months per year in our area. With a better understanding of the disease, how it is transmitted and prevention options, you will be able to make an educated, healthier choice for your pet.  

Fortunately for our pets, heartworm is not so easy to contact in the Northeast. However, with rescue groups bringing so many dogs from the South to this area now, it has become more prevalent. Per “The Heartworm Handbook” by Melinda Miller, Hospital Director of Smith Ridge Veterinary Center, the mere presence of mosquitoes isn’t enough for a pet to be infected with the parasite. Heartworms have a very complex lifecycle that requires specific species of mosquito and precise timing as the mosquito has to have bitten previously infected animals in order for it to pick up and transmit larvae. Even more important: the larvae picked up by the mosquito can’t mature inside the mosquito and be infective to other animals until there are at least 8 to 14 continuous days of temperatures above 57 degrees day and night.  

Since our temperatures in the Northeast limit the potential for exposure to heartworm, is it imperative to treat your pets every month? Heartguard and other treatments are not harmless. They are systemic pesticides. To eliminate unnecessary doses of toxic chemicals for your pet, Smith Ridge Veterinary Center, an integrative veterinary practice in South Salem, NY, recommends the following protocol:

In May of each year: run a SNAP test. If the test is clear, begin administering a heartworm preventative such as Heartgard or Interceptor. These preventatives are proven by research to be 100% effective when given every 45 days. The drug manufacturers convinced the FDA that the public couldn’t remember to administer the preventatives unless it was on a 30 day schedule, despite the fact that they are effective for 45 days (and beyond). That’s the only reason they are labeled for 30 day use. So, as long as you fully comply with the schedule below, the Smith Ridge preventative recommendation for this area is:

June 1 – dose 1 (will kill infection that began between April 15 and May 31)
July 15 – dose 2 (will kill infection that began between June 1 and July 15)
August 31 – dose 3 (will kill infection that began between July 16 and Aug. 31)
October 15 – dose 4 (will kill infection that began between Sept. 1 and Oct. 15)

As you can see above, heartworm preventatives don’t actually prevent infection, they just prevent larvae from maturing into adult worms. It’s the adults that cause harm. These drugs “reach back” to kill off any larvae that may be present. If there is no infection present, your pet is getting toxic chemicals it doesn’t need. The start date of June 1 is actually very conservative as typical April and May temperatures aren’t usually above the 57 degree mark for 8 to 14 days on a 24 hour, continuous basis. And infective transmission won’t occur until that happens. While the use of these toxic chemicals may be a necessary evil, the above schedule at least allows you to minimize your pet’s exposure to them.

Important Note: if you travel with your pet to areas of the country where there are warmer temperatures during the year, this protocol must be adjusted.

There are pet owners who want to eliminate the use of preventatives completely. That can be done, though it does require using 2 different tests and testing twice during the year – and there is still some risk. We recommend you work with a veterinary practice like Smith Ridge if you want to avoid administering preventatives completely.

Think through your options and choose wisely for your pet.