A Modified Heartworm Preventative Approach

Cooler weather is starting to set in which has me thinking about heartworm. Heartworm is a disease spread through mosquitoes, making transmission impossible during the winter months. We generally like to limit our dog’s exposure to chemicals and medication, so this topic has been on my mind for a while. I will admit that even I had tried to research what would be the best practice for our region/lifestyle and quickly found myself in over my head. Dejected, we decided to stop administering heartworm medication around November and start up again when the weather warmed. I knew however that there had to be a better, more scientific solution. 

I finally found that solution in an amazing handout, written by Smith Ridge Veterinary Center. We decided to use what is referred to as “Approach Two” below. For us, the level of chemical exposure was acceptable considering the amount of protection and convenience. Below is an excerpt that includes the two approaches that Smith Ridge recommends.

“Heartworm disease is a serious parasitic disease that can cause damage to your pet’s heart, as well as other organs. It is even potentially fatal. It is also a disease with very complex transmission and life cycle requirements. Because of that, there are options in how to approach the prevention and transmission of this disease. As you will often hear at Smith Ridge, there is no “one size fits all” method for health. 

Our basic recommendations are listed here in Part 1, along with some answers to the most frequently asked questions. Then, for those who are interested, there is a Part 2 with an in-depth, comprehensive explanation of every phase of heartworm disease, prevention and treatment. 

Smith Ridge currently recommends one of the following two methods of monitoring and/or preventing heartworm disease in dogs who live in our geographic area, or in similar northern climates. Dogs who live in, or who visit (for even a day), areas where there are higher temperatures than those in the northern half of the U.S. must follow a different protocol than the ones discussed here.

APPROACH ONE – Monitoring only

In late April or May of each year: run TWO heartworm screening tests at the same time 

Test 1: a SNAP test – this is an in-office blood test that can detect the presence of adult, female worms 

Test 2: a microfilaria test – this is a laboratory blood test that detects the presence of “baby” heartworms 

With this monitoring-only approach, you will not be administering preventative medication. Because of that, you MUST run both of the tests mentioned above AGAIN in November or December. 

Running both of these tests, *twice* a year, will ensure that any possible heartworm infection will be detected early so that the more mild, “slow kill” method of treatment can be used. 

Note: there is a chance that any dog could have a male-only infection which would not show on either of the 2 noted tests. This would be a fairly rare occurrence. There are no inexpensive or truly accurate screening tests for male-only heartworm infections. But single sex infections, whether all male or all female, are self-limiting as no reproduction can take place. Infection would end when the worm(s) died. 

Since you aren’t using preventatives with this monitoring-only approach, you may want to administer homeopathic or herbal preparations that are believed to prevent/treat heartworm. Discuss this with your veterinarian.

APPROACH TWO –  Conventional screening and modified preventative program

In May of each year: run a SNAP test 

If the test is clear, begin administering a heartworm preventative such as Heartgard or Interceptor. 

Despite the label instructions for administration every 30 days, these preventatives are proven by research to be 100% effective when given every 45 days. So, you can minimize the amount of chemicals being administered by using a 45 day schedule. The schedule we recommend in this area is: 

June 1 – dose 1 

July 15 – dose 2 

August 31 – dose 3 

October 15 – dose 4 2

You do not need to run another SNAP test in the fall for heartworm if you’ve been using the preventatives as scheduled above. However, remember that the SNAP panel tests for 3 tick-borne diseases (Lyme, Ehrlichia, Anaplasmosis) in addition to heartworm. Due to the very high incidence of tick-borne diseases in our area, we do recommend two screenings per year.”

If you want a more detailed explanation, the full version of the handout will be available in my Google drive folder.

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