Advice from Dr. Chris: Can I Stop Using a Flea/Tick or Heartworm Preventative in Winter?

Authored By: Chris Vanderhoof DVM, MPH

It’s late February and for many in the US, it’s the peak of some pretty frigid temperatures with winter storms bringing plenty of snow and ice. For many it is also the time to take a break from reminders to give their dogs preventative products against fleas, ticks, and heartworms.

After all, it certainly seems less likely to see these bugs around, especially when there’s a thick layer of snow on the ground and nature seems to be at a standstill.

Some research seems to confirm this view. According to a study published in Parasites and Vectors in 2017, of over 500 pup parents, the average owner responded that their pets needed about 10 months of prevention. But even so, based on product purchases, the average pet coverage was actually only 6 months. 

It also makes sense that folks living in warmer regions would recognize the need to use preventatives more regularly while folks in colder regions would see less need at certain times of the year, believing these creepy crawlies are dead like most everything else for at least a couple of months.

And study findings confirm this view too. While opinions varied, the folks responding from the Northeast believed their dogs needed less prevention compared to other regions.

But do these critters really die during the winter like many believe? If they come back to plague our pups year after year, where do they actually go when it gets colder? Is there such a thing as a flea and tick season, especially in colder climates?

In 2019, a video went viral that was posted by the staff of a local veterinary hospital in Boston, New Hampshire in early January, of a dog who got into an unfortunate altercation with a porcupine. While sedated to have the quills removed and wounds cared for, a fully engorged tick was found embedded in the dog’s skin. This occurred with several inches of snow on the ground. 

Why did the video go viral? People were shocked. In one of the coldest states in the US, well-known as a winter sports destination, in the middle of winter, a dog actually had an embedded tick.

It would seem that ticks don’t really die just because it gets cold or because there’s snow on the ground.

In fact, as staff of the vet hospital in New Hampshire attested to in interviews, some ticks remain dormant (but not dead) while others stay active. Ticks can overwinter very well beneath a layer of snow, hanging around the walking paths that dogs and their owners trample out. 

While a misperception of the seasonal activity of ticks is more understandable in the coldest northeast, this idea of a defined “tick season” stretches very far south even to at least my region of Virginia where winters are certainly milder than in New Hampshire, but we still get at least a couple of snow and ice storms a year.

I find not infrequently that folks believe ticks and other bugs are largely gone after the first official frost that occurs in late fall. But if ticks survive well in a US state that stays pretty well snow-covered for at least 4-5 months of the year, one single frost in a milder climate region is very unlikely to do much to them.

My own mother, an avid gardener, attended a Master Gardener’s conference here in Virginia a couple of years ago. Included in the conference was a great deal of information about ticks, with gardeners naturally being at higher risk of exposure.

To illustrate just how resilient ticks are, one of the speakers had frozen a tick in a small block of ice. While he lectured, he allowed the block of ice to thaw on camera. By the end of his lecture, the block of ice had melted and the tick was crawling around.

In Virginia, we see changes in temperature and weather all throughout the winter. As I write this, it was a brisk 22 degrees just two days ago. This morning? It was a balmy 60 degrees. It’ll probably stay warm for about 1-2 more days before it gets below freezing again.



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