It’s a Tuesday evening in late April. The backyard gate has been open for an hour already, and your dog has found her fifth interesting patch of grass to sniff. You’re not worried, exactly. It’s just that familiar spring feeling: the ticks are out, the mosquitoes are starting to hum, and you’re standing there with your coffee thinking “should I be doing something about this?”
That moment of quiet wondering is where most of us start. We are not here to panic you out of your backyard. We are here because that question deserves a real answer, backed by what veterinarians and parasitologists are actually seeing in 2026.
Here’s what’s spreading, what actually works, and why we made the choices we made for our own dogs.
Heartworm Is Moving North
Heartworm has always been concentrated in the South. That is no longer the full picture.
The Companion Animal Parasite Council (CAPC) forecast for 2026 shows heartworm risk expanding beyond its traditional stronghold in the Southeast, spreading northward along the Mississippi River corridor and up the Atlantic coast. The forecast also identifies persistent pockets of elevated risk in parts of the Mountain West and Northern California, areas that were not historically considered endemic.
The parasite itself is transmitted by mosquitoes. A single infected bite can deposit larvae into your dog’s bloodstream, where they mature over about six months into worms that live in the heart and pulmonary arteries. According to the American Heartworm Society, treatment exists but is expensive, carries real risk of complications, and involves months of strict exercise restriction. It is not something you want your dog to go through.
Prevention is dramatically easier than treatment. That is the core of why we do what we do.
Lyme Disease Is No Longer Just a Northeast Problem
Lyme has been entrenched in the northeastern United States for decades. CAPC’s 2026 forecast projects it spreading into new counties across Ohio, Kentucky, West Virginia, Tennessee, North Carolina, Indiana, Illinois, and Michigan, with sustained risk pushing westward into the Northern Plains.
Lyme is tick-borne. The blacklegged tick (Ixodes scapularis) carries the bacterium Borrelia burgdorferi, and its range has grown significantly over the past decade. Dogs who spend any time outdoors, even in their own backyard, are at exposure risk in affected areas.
The tricky part: Cornell’s College of Veterinary Medicine notes that only a small percentage of infected dogs show clinical signs of Lyme disease. Many dogs carry the bacteria with no visible symptoms, which means the disease can progress silently. That is why testing and prevention matter even if your dog seems perfectly healthy.
The Tick Diseases You Might Not Know About
Ehrlichiosis and anaplasmosis are both tick-borne diseases that CAPC has flagged as actively expanding in 2026. Ehrlichiosis risk remains high across the Southeast, Southwest, and south-central United States, with lone star tick ranges pushing northward into the Upper Midwest and New England. Anaplasmosis risk is climbing in parallel with Lyme expansion as the same blacklegged tick populations spread into new territory. According to the American Kennel Club, both diseases can cause fever, lethargy, joint pain, and in severe cases, bleeding disorders or organ involvement.
Here is the part that surprises most dog owners: according to the CAPC, these diseases are not covered by the most common heartworm preventives. If you are giving your dog a monthly oral heartworm pill, that pill is doing exactly one thing: preventing heartworm. It is not killing ticks. It is not treating Lyme or ehrlichiosis or anaplasmosis.
That distinction matters. A lot.
What We Use and Why
We keep Hazel and Kaia on year-round prevention specifically because of how aggressive these parasite ranges have gotten. We do not wait for summer. We do not wait for the first mosquito. The CAPC and the American Heartworm Society both recommend year-round prevention, and we follow that guidance.
For flea and tick protection, we use K9 Advantix II for both of our dogs. It is a topical applied monthly that kills and repels fleas, ticks, and mosquitoes. Most topical products kill fleas and ticks but do not address mosquitoes. K9 Advantix II does, which was the deciding factor for us: we wanted one product covering both tick-borne and mosquito exposure.
The Daily Dog earns commissions from qualifying purchases through affiliate links. We only recommend products we have personally used with Hazel or Kaia and clearly note what has helped them.
One thing we want to be clear about: K9 Advantix II is not a heartworm preventive. Repelling mosquitoes reduces the chance of a bite, but it does not replace an actual heartworm preventive that kills larvae in the bloodstream.
Year-Round Versus Seasonal: The Debate Is Over
You will still find older articles online recommending “seasonal” prevention, loosely defined as spring through first frost. That guidance has shifted.
Both CAPC and the American Heartworm Society now recommend year-round prevention for heartworm, and the AHS’s updated canine heartworm guidelines reinforce macrocyclic lactone preventives as the cornerstone of heartworm management. The reasoning is straightforward: you cannot reliably predict when the last mosquito or the first tick will appear, and the cost of year-round prevention is a fraction of the cost of treating a heartworm infection.
For flea and tick, the same logic applies. Milder winters mean ticks are active in more months than they used to be. Some areas of the country now see tick activity year-round. The “seasonal” approach assumes a predictable window, and that window is no longer predictable.
What To Do Next
If you are standing in that backyard moment right now, wondering whether to renew or switch or start, here is what we suggest.
Ask your vet what parasites are active in your specific county or zip code. Regional pressure varies, and CAPC offers 30-day parasite forecast maps that can help you and your vet assess local risk. Understand what your current prevention product actually covers. If it is an oral heartworm preventive, verify whether it addresses ticks. If it is a flea and tick product, verify whether you also have heartworm prevention in place. Consider year-round coverage if your area shows tick or mosquito activity beyond traditional seasons. And test annually. Most vets include Lyme, ehrlichiosis, and anaplasmosis in your dog’s annual heartworm screening test (often called a 4Dx test). If yours does not, ask for it.
If your dog is dealing with spring allergies on top of parasite season, our natural remedies for dog allergies guide covers what actually helps. And for a broader look at how your dog’s immune system connects to all of this, our article on dog gut health digs into why the immune system starts in the gut.
We are not veterinarians. We are dog owners who read the forecasts and made an informed decision for our own family. That is exactly what we are offering here: the information we used, so you can make your own call.
This article is for general educational purposes and is not veterinary medical advice. Always consult your veterinarian for a prevention plan tailored to your dog’s health and your local parasite risk.
Tyler Tilton
I do not write surface-level dog advice. When our dog got sick, I learned the hard way that most of what is out there is recycled, watered down, or just wrong. I started The Daily Dog to be the resource I could not find, the one that goes deeper, asks harder questions, and gives you the full picture so you can make real decisions for your dog.
