(616) 498-1316
Posts » Current Post

Heartworm Prevention is Vital for Dogs – And Cats Too!

March 1st, 2021 by Laurie Brush

It’s tempting to skip heartworm medication during winters in Michigan when infectious mosquitoes seem a distant memory. It’s also hard to remember to restart preventative treatment before our wily weather teases us with unseasonal warmth.

Foregoing year-round prevention is like playing Russian roulette with your canine companion’s heart.

“Mosquito species are constantly changing and adapting to cold climates and some species successfully overwinter indoors as well. Year-round prevention is the safest, and is recommended by the American Heartworm Society,” said Dr. Laurie Brush, founder of Heaven at Home Pet Hospice.

“The consequences of skipping prevention can be fatal.”

Heartworm disease is complex, and causes lasting damage to the heart, lungs, kidney, liver and arteries even if your pet survives.


Transmission begins when an infected mosquito carrying microscopic larvae, called microfilaria, feeds on your dog. The microfilaria mature into “infective stage” larvae over 10-14 days. In as few as 51 days, immature heartworm larvae can molt into an adult stage, which cannot be effectively eliminated by preventives. Within 6 months, fully adult heartworms will grow to be a foot long and will begin multiplying, wreaking havoc on the cardiovascular system. Mature heartworms can live for 5 to 7 years.

The resulting damage can affect the dog’s health and quality of life – if he or she survives — long after the parasites are gone.


By the time your dog shows symptoms, damage has already begun. In early stages, you may notice a chronic cough, fatigue, decreased appetite and weight loss, with a swollen abdomen in later stages.

Severe cardiovascular collapse, called caval syndrome, may follow and is marked by a sudden onset of labored breathing, pale gums, and dark bloody or coffee-colored urine. Without prompt surgical removal of the heartworm blockage, few dogs survive.

If caught in time through annual testing, it can still be expensive and painstaking to treat. Dogs undergoing treatment must have their activity level severely restricted for 6-8 weeks to avoid sudden circulatory blockages from dead parasite fragments.

While cats are a less hospitable environment for heartworms, they also cannot be treated if infected. Immature worms can cause heartworm-associated respiratory disease in felines.

In each case, prevention is by far the best option, via monthly pills, monthly topicals or a six-month injectable product.

Don’t risk missing a dose in this high-stakes disease. The best protection is to treat your fur-friends year-round.