As spring arrives and mosquitoes return, many veterinary clinics remind clients about heartworm disease. It is a serious condition, but it is also one that veterinarians have well-established tools to help prevent. The details of testing and prevention depend on where you live and on your individual pet, so the most useful thing you can do is understand the basics and bring good questions to your vet.
What heartworm disease is
Heartworm disease is caused by a parasitic worm that can live in the heart, lungs and associated blood vessels of infected animals. It is spread by mosquitoes. When a mosquito bites an infected animal, it picks up immature worms, and those can then be passed to another animal through a later bite. Over time, the worms can mature and cause damage to the heart, lungs and blood vessels.
Dogs are considered a natural host, which means the worms can mature and reproduce inside them. Cats can also be infected, although the disease behaves differently in cats, and it can be serious even with a small number of worms. Indoor cats are not completely protected, since mosquitoes can get inside homes.
Why early signs are easy to miss
In the early stages, many infected dogs show few or no signs. As the disease progresses, owners may notice things like a persistent cough, tiring easily during exercise, decreased appetite or weight loss. Signs in cats can be vague and may include coughing, breathing difficulty or vomiting. Because these signs overlap with many other conditions, only a veterinarian can sort out what is going on.
That is a big reason testing matters. Your veterinarian can test for heartworm with a blood sample and will advise how often your pet should be tested.
Questions to ask at your next visit
- Is heartworm a concern where we live, and where we travel with our pet?
- Does my dog need a heartworm test before starting or continuing prevention, and how often should we retest?
- What prevention options are appropriate for my pet’s age, weight, species and health?
- Should my pet be on prevention year-round, or only during part of the year?
- What should I do if I miss a dose or give it late?
- For cats: what do you recommend for my indoor or outdoor cat?
Many veterinarians recommend year-round prevention, but your vet will give you advice based on your region and your pet.
Prevention is a routine, not a one-time event
Heartworm preventives are typically given on a regular schedule. The most common problem is not the product but the routine: doses get forgotten when life gets busy. A few habits help. Set a recurring reminder on your phone, keep a log on the box or a calendar, and tie the dose to an easy-to-remember date. If you have several pets, track each one separately.
Only use products your veterinarian prescribes or recommends, and give them exactly as directed. Products made for dogs and cats are not interchangeable, and dosing depends on your pet’s weight.
Reducing mosquito exposure around your home, such as emptying standing water from buckets, planters and toys, is a sensible extra step. It does not replace prevention, but it makes your yard more pleasant for everyone.
