Down the Rabbit Hole: Preventing Heartworm and Lyme Disease in Dogs
- Katherine Goliboski
- 2 hours ago
- 7 min read
We wish our dogs could live forever in perfect health. We understand that they depend on us, their caretakers, to offer them the best resources to achieve this aim. It is our responsibility to do everything we can to safeguard our dogs, which involves not only fulfilling their mental and physical needs but also utilizing the available technology and science to help preserve their lives.
Two serious diseases that threaten dogs’ well-being are heartworm and Lyme disease. Both can cause severe health problems and require costly, lengthy treatments. The good news is these diseases can be completely prevented with veterinary-prescribed medications. This guide explains how heartworm and Lyme disease affect dogs, how they are transmitted, and why prevention through medication is the safest and most effective choice.
How Heartworms Affect Dogs
Heartworm disease is caused by a parasitic worm called Dirofilaria immitis. These worms live in the heart, lungs, and associated blood vessels of infected dogs. The disease starts when a mosquito carrying heartworm larvae bites a dog, transferring the larvae into the bloodstream.
Once inside, the larvae mature into adult worms over several months. These worms can grow up to a foot long and infest the heart’s right ventricle and pulmonary arteries. The presence of heartworms causes inflammation and damage to the heart muscle and blood vessels. Over time, this damage leads to:
Reduced heart function
Blocked blood flow
High blood pressure in the lungs
Heart failure
Dogs with heartworm might exhibit symptoms such as coughing, fatigue, breathing difficulties, and weight loss. However, they can also remain symptom-free until the disease progresses to a critical stage, causing severe symptoms. At this point, the condition could become terminal, making treatment ineffective or too risky for the dog. Without treatment, heartworm disease can be deadly. Click here to see a very detailed video explaining heartworm and their life cycle - warning, it is graphic in parts.
The Complexity of Heartworm Treatment
Treating heartworm disease is challenging because killing the adult worms too quickly can cause dangerous complications. When the worms die, they break apart and can block blood vessels, leading to severe inflammation, blood clots, or even sudden death.
Veterinarians follow a careful, staged treatment plan to minimize risks:
Initial stabilization: Dogs receive medications to reduce inflammation and control symptoms.
Killing immature worms: Medications target younger worms before they mature.
Adulticide therapy: A series of injections kills adult heartworms slowly over weeks.
Restricted activity: Dogs must limit exercise to reduce strain on the heart during treatment. Increased blood flow could lead to dead worm tissue moving too quickly through the system and causing blockages.
This process can take several months and requires close veterinary supervision. The cost and stress of treatment highlight why prevention is critical.
How Lyme Disease Affects Dogs
Lyme disease is caused by the bacterium Borrelia burgdorferi, transmitted through the bite of infected black-legged ticks (also called deer ticks). When a tick attaches to a dog for 24-48 hours, it can transmit the bacteria into the dog’s bloodstream.
Once infected, dogs may develop symptoms such as:
Fever
Lameness or swollen joints
Loss of appetite
Fatigue
If untreated, Lyme disease can cause serious complications like kidney damage and chronic arthritis.
Treatment Challenges for Lyme Disease
Lyme disease is treatable with antibiotics, but treatment is not quick or cheap. Dogs typically require at least four weeks of the antibiotic Doxycycline, and some may need longer courses if symptoms persist.
The cost of treatment includes veterinary visits, diagnostic tests, and medications. Additionally, Lyme disease can cause long-term health issues even after treatment, making prevention a better option.
How Heartworm and Lyme Disease Are Transmitted
Understanding how these diseases spread helps explain why prevention is so effective.
Heartworm: Mosquitoes pick up heartworm larvae from infected animals (including affected dogs). When they bite a healthy dog, they transmit the larvae. Mosquitoes are active in warm months and in many regions year-round (often when the temperature is around 15 degrees Celsius or higher).
Lyme disease: Ticks become infected by feeding on wild animals like deer and mice. Infected ticks latch onto dogs during outdoor activities, especially in wooded or grassy areas.
Both diseases rely on vectors—mosquitoes for heartworm and ticks for Lyme disease—to spread. Controlling exposure to these vectors is difficult, so relying on medications that kill larvae or bacteria inside the dog is the most reliable defense.
.
Veterinary Medications That Prevent Heartworm and Lyme Disease
Veterinarians prescribe specific medications that prevent these diseases effectively:
Heartworm Preventatives
These medications kill heartworm larvae before they mature into adults. They come in various forms:
Monthly chewable tablets
Topical liquids applied to the skin
Injectable formulations lasting six or twelve months
Common active ingredients include ivermectin, milbemycin oxime, and moxidectin. These preventatives are highly effective when given consistently. Missing doses or stopping treatment increases the risk of infection.
Lyme Disease Prevention
Preventing Lyme disease focuses on tick control and vaccination:
Tick preventatives: Spot-on treatments, collars, and oral medications kill ticks before they can transmit bacteria.
Lyme vaccine: Some dogs benefit from a vaccine that helps their immune system fight Borrelia burgdorferi.
Veterinarians recommend a combination of tick control and vaccination based on the dog’s lifestyle and regional risk. Although there is concern by many that these chemicals can be harmful to animals, in this case the ends justify the means, and unfortunately natural treatment methods are just not effective enough.
Keeping your yard clear of leaf build up and long grasses/plant growth can also reduce the areas for ticks to reside. Being careful to visit only short grass areas may help as well.
Why Prevention Is Better Than Treatment
Treating heartworm or Lyme disease is expensive, time-consuming, and stressful for dogs and owners. Prevention through veterinary medications offers several advantages:
100% effective when used properly: Medications kill parasites before they cause harm.
Avoids health risks: Prevents heart and lung damage from heartworms and joint/kidney issues from Lyme disease.
Saves money: Preventative medications cost far less than treatment and follow-up care.
Protects other pets: Reduces the spread of disease in the community.
Tips for Effective Prevention
To keep your dog safe, follow these guidelines:
Give heartworm preventatives year-round, even in winter if recommended by your vet.
Use tick preventatives consistently, especially during tick season.
Check your dog daily for ticks after outdoor activities.
Schedule regular veterinary check-ups and heartworm tests.
Real-Life Example
As a teenager in the early 2000's, our first dog came to us in something out of a movie.
One October night, we were driving through Oshweken and stopped at a gas station to refuel. My mom left the side door of the van open while retrieving her purse, leaving the seat next to me vacant. As she was occupied with the attendant, a Husky-like dog leapt into the seat. She was stunning, with reddish/auburn fur mixed with white, intelligent amber eyes, and delicate paws.
I was happily petting her when my mother returned. However, mom, laughing, guided the dog out of the car, and we continued on our way.
About four hours later, around midnight, we drove past the gas station again and saw the dog sitting under the lights. My mother slowed down and quickly decided to bring the dog home for the night, planning to speak with the attendants the next morning to find the owner, as she drove through Oshweken daily.
On the way home, I gazed at the full moon and, with the relatively new movie Blair Witch Project in mind, decided to name her Blair.
It turned out Blair belonged to the gas station owner, and after mom contacted her, it was decided that the best place for Blair was with us.
I was thrilled!
We took her to our vet for a check-up, heartworm test, and vaccines. The test was negative, and although she was slightly underweight, she seemed healthy.
Fast forward four months. Blair's kennel was in the basement, and before school, I would take her out in the backyard, then put her back to bed with her breakfast; she was her usual self. At lunchtime, while at my grandmother's with my dad and sister, mom called.
Blair had collapsed during their walk. Mom rushed her to the vet. She tested positive for heartworm, and her heart and lungs showed signs of laboured function. The doctor discussed the options of a lengthy, expensive treatment (which was risky but possible), taking her home (with the understanding of a short life expectancy), or euthanasia. Mom wanted to talk to me first, as she was my dog, before making a decision. They would keep her on oxygen and monitor her until we chose. I was too shocked to decide at first. Mom said they expected she would be okay until after school, so I could tell her then. I sat in math class, trying hard not to cry—I was only 13, and life and death decisions were beyond me. As soon as I got home, I told my mom we should treat her, and I would find a way to pay. But mom said it was too late. Around 2 p.m., the vet called her to say Blair had passed, indicating she wouldn't have responded to treatment anyway; it had been too late.
The vets suspected her initial heartworm test was a false negative due to the early stages of infection. She had come from a high risk area due to the proximity of the Grand River, and her history of living in Northern Ontario. Today, this could have been prevented.
Final Thoughts on Protecting Your Dog
Heartworm and Lyme disease pose serious threats to dogs but can be completely prevented with veterinary-prescribed medications. Understanding how these diseases affect your dog and how they spread helps you appreciate the importance of prevention.
By committing to regular use of heartworm preventatives, tick control products, and Lyme vaccination when appropriate, you protect your dog’s health, save money, and avoid the stress of complicated treatments. Talk to your veterinarian today about the best prevention plan for your dog’s lifestyle and location.
Comments