Hey there fellow dog lovers! If you’re reading this you probably care a ton about your four-legged companion and want to make sure they’re protected from one of the nastiest parasites out there – heartworms. As a dog parent myself, I know how worrying it can be to think about these dangerous little critters setting up shop in your pup’s heart and lungs.
Let’s cut straight to the chase: checking your dog for heartworms is absolutely crucial, and it’s not something you should skip or postpone. In this article, I’m gonna break down everything you need to know about heartworm testing for your doggo – from what heartworms actually are (ick!) to how vets test for them and how often you should be getting your pup checked.
What Are Heartworms Anyway?
Before we jump into testing, let’s understand what we’re dealing with Heartworm disease is a serious and potentially fatal condition caused by foot-long worms (yes, FOOT-LONG!) called Dirofilaria immitis that live in the heart, lungs, and blood vessels of infected pets. These nasty parasites cause severe lung disease, heart failure, and damage to other organs
The real kicker? These worms can live for 5-7 years in dogs. That means each mosquito season can lead to more and more worms piling up in your poor pup’s system if they’re not protected.
How Dogs Get Heartworms
Your dog can’t catch heartworms directly from another dog The only way dogs get infected is through mosquito bites, Here’s how it happens
- A mosquito bites an infected animal and picks up baby heartworms (microfilariae)
- These baby worms develop into “infective larvae” inside the mosquito over 10-14 days
- The mosquito bites your dog, depositing larvae onto their skin
- The larvae enter through the bite wound and migrate through your dog’s body
- About 6 months later, these larvae mature into adult heartworms in your dog’s heart and lungs
- Adult worms mate and produce more baby worms, continuing the cycle
Scary, right? And the worst part is that heartworm disease has been diagnosed in all 50 states, so no dog is completely safe without prevention.
Signs of Heartworm Disease in Dogs
In early stages, many dogs show few or no symptoms at all. That’s what makes testing so important! As the disease progresses, you might notice:
- A mild, persistent cough
- Reluctance to exercise
- Fatigue after moderate activity
- Decreased appetite
- Weight loss
In advanced cases, dogs can develop:
- Heart failure
- A swollen belly due to excess fluid
- Labored breathing
- Pale gums
- Dark or coffee-colored urine (in cases of caval syndrome, which is an emergency!)
But here’s the thing – by the time you notice these symptoms, the disease is already causing lasting damage to your furry friend’s heart and lungs. That’s why testing and prevention are so darn important!
How Vets Check Dogs for Heartworms
OK, so now let’s get to the main question: how do you actually check a dog for heartworms?
The Two Main Tests for Heartworm Detection
Heartworm testing is pretty straightforward and involves two main tests:
1. Antigen Test (Testing for Adult Worms)
This is the primary test vets use to detect heartworm infection. It specifically looks for proteins (antigens) released by adult female heartworms.
- Requires just a small blood sample
- Can detect infections with as few as 1-3 adult female worms
- Results are usually available quickly (sometimes during your office visit)
- Highly accurate but not 100% foolproof
However, this test has limitations. It will be negative if:
- The infection is less than 5-7 months old (too early for adults to be present)
- All worms are male or immature females
- There are very few worms (antigen level too low to detect)
- There are technical issues with the test
2. Microfilaria Test (Testing for Baby Worms)
This second test looks for the baby heartworms (microfilariae) circulating in the bloodstream. The most common methods are:
- Modified Knott’s test: Uses a centrifuge to concentrate microfilariae for detection
- Filter test: Passes blood through a fine filter that traps microfilariae
This test confirms that mature adult worms are present and reproducing. It can also be negative for several reasons:
- The adult worms aren’t mature enough to mate
- All adult worms are the same sex
- There are too few microfilariae to detect
Additional Tests Sometimes Used
If blood tests are negative but your vet still suspects heartworm disease, they might recommend:
- X-rays (Radiographs): Can show heart enlargement and swelling of the pulmonary artery
- Electrocardiogram (EKG): Helps detect abnormal heart rhythms and chamber enlargement
- Echocardiography (Heart Ultrasound): Can actually visualize heartworms within the heart and pulmonary artery
When Should Your Dog Be Tested for Heartworms?
The American Heartworm Society recommends yearly testing for all dogs over 7 months of age. But there are some specific situations when testing is especially important:
For Puppies:
- Puppies under 7 months can start heartworm prevention without testing
- First test should be done at 7 months of age
- Test again 6 months later
- Then yearly after that
For Adult Dogs New to Prevention:
- Test before starting heartworm prevention
- Test again 6 months and 12 months later
- Then annually after that
If You’ve Missed Doses of Preventive:
- Immediately restart monthly preventive
- Retest 6 months later (heartworms must be about 7 months old before infection can be diagnosed)
When Switching Preventive Medications:
- Test before making the change to ensure your dog is heartworm-free
When Adopting a Dog:
- Test at adoption if the dog’s history is unknown
- If negative, test again 6 months later to be sure
Why Annual Testing Is Important (Even If Your Dog Is On Prevention)
I get this question a lot – “My dog is on heartworm preventive all year, so why do they need annual testing?” Here’s the deal:
- We’re human and we forget stuff: Even the most dedicated pet parents might forget a dose or give it late.
- Dogs are sneaky: Your pup might spit out or vomit their medication without you noticing.
- Weight changes matter: If your dog’s weight increases, they might need a different dosage.
- No medication is 100% effective: In rare cases, dogs can become infected despite proper prevention.
Annual testing is the ONLY way to know for sure if your dog is heartworm-free. And trust me, catching an infection early is way easier (and cheaper!) than treating an advanced case.
What Happens If Your Dog Tests Positive?
If your dog’s heartworm test comes back positive, don’t panic! Most infected dogs can be successfully treated. Here’s what typically happens:
- Confirm the diagnosis: Your vet will likely run a second, different test to be absolutely sure.
- Restrict exercise: This is super important! Physical activity increases the damage heartworms cause.
- Stabilize your dog: Before treatment begins, your vet will make sure your dog is stable enough for treatment.
- Administer treatment: This usually involves medication to kill adult worms and another to kill microfilariae.
- Follow-up testing: About 9 months after treatment, your vet will test again to confirm all heartworms are gone.
Treatment can have side effects as dead worms are pumped from the heart into the lungs. That’s why keeping your dog calm and quiet during and after treatment is essential.
Prevention: The Best Way to “Check” for Heartworms
The absolute best approach to heartworm disease is to prevent it in the first place! The American Heartworm Society recommends you “think 12”:
- Get your pet tested every 12 months
- Give heartworm preventive 12 months a year
Preventive medications are highly effective and available in several forms:
- Monthly chewable tablets
- Monthly topical treatments
- Injections that last 6-12 months
These require a prescription from your vet, and for good reason – your vet needs to make sure your dog isn’t already infected before starting prevention.
My Personal Experience with Heartworm Testing
I’ll never forget when my neighbor’s dog tested positive for heartworms. They had skipped a few months of prevention during winter, thinking mosquitoes weren’t active. Big mistake! Their sweet Lab mix had to go through the whole treatment process, which was stressful for everyone. The restricted activity was especially hard – imagine trying to keep an energetic Lab calm for weeks!
That experience made me super vigilant about my own pup’s prevention schedule. I’ve got reminders set on my phone, and we NEVER miss a dose, even in the dead of winter. The annual testing gives me peace of mind, knowing we’re doing everything possible to keep those nasty worms away.
Takeaway: Don’t Skip Those Tests!
Heartworm testing is a simple, relatively inexpensive procedure that can literally save your dog’s life. Here’s what to remember:
- Heartworm disease is present in all 50 states
- All dogs should be tested annually
- Prevention is far easier and cheaper than treatment
- Early detection through regular testing is key to successful treatment
- Both indoor and outdoor dogs need testing and prevention
So, call your vet today if your pup is overdue for their heartworm test! Your furry best friend depends on you to keep them safe from these dangerous parasites.
Remember, when it comes to heartworms, the old saying really is true: an ounce of prevention is worth a pound of cure. Or in this case, a simple blood test is worth avoiding a serious, potentially fatal disease.
Has your dog had their annual heartworm test? Drop a comment below – I’d love to hear about your experiences with heartworm testing and prevention!
My dog has heartworms. My veterinarian recommends a series of injections, hospitalization, pain medication, and lab work to safely treat my pet. Is there any other treatment available?
Your veterinarian is recommending what is best. Only one drug, which is called melarsomine, is approved by the U.S. Food and Drug Administration (FDA) for treatment of heartworm infection in dogs; this drug should be administered by injection in the veterinary hospital. Although there are some risks associated with this medication’s use, most adult worms die quickly and can be eliminated within 1 to 3 months. Cage rest and drastically restricted exercise during this period can decrease the chances of complications from treatment.
Along with melarsomine, the heartworm treatment protocol recommended by the American Heartworm Society includes several other medications that help improve the chances of treatment success and reduce the incidence of side effects. This includes administering a heartworm preventive medication to an infected dog for 2 months prior to melarsomine treatment. Long-term, continuous use of heartworm preventives alone to treat heartworm infections, however, is not recommended as an alternative to melarsomine, because it is well documented that additional damage to the heart and lungs occurs the longer adult heartworms are present.
My dog has heartworms. My vet started her on monthly prevention before he started treatment. Is this OK?
Yes, it is recommended in the American Heartworm Societys Guidelines to do so. This should be done under the direct supervision of a veterinarian because dogs with microfilaria (baby worms in the blood that the mosquito picks up when feeding) could possibly have a reaction to the preventive. And while this is an extra-label use of heartworm preventives, it is appropriate under the supervision of a veterinarian. However, it is important that your veterinarian assesses the severity of the disease and chooses the proper preventive accordingly. By starting the prevention program you are ensuring that your dog will not get a new heartworm infection while being treated for the existing heartworm disease. Furthermore, you are helping to keep your dog from being a source of heartworm larvae (microfilaria) for mosquitoes to pick up and eventually infect other dogs. This approach makes the treatment of the existing infection more effective.
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FAQ
How do you test for heartworms in dogs?
Testing for heartworms in dogs is a two-part process. The first step is an antigen test that detects a specific protein released by adult female heartworms, indicating the presence of adult heartworms.
When should a dog get a heartworm test?
Annual testing is recommended for dogs to promptly detect infections and minimize damage. Puppies under five months of age are too young to test positive for heartworm disease. In regions where heartworm disease is less common, diagnosis may occur during a work-up for heart disease based on imaging tests like radiographs and ultrasound.
How do I know if my dog has heartworms?
Radiographs can indicate heartworm infection by showing specific problems in the right side of the heart. Ultrasound can measure heart thickening and visualize live worms. Imaging tests can lead to further antigen or microfilaria testing. Annual testing is recommended for dogs to promptly detect infections and minimize damage.
Can a snap test diagnose heartworm disease in dogs?
Many veterinarians use a rapid-result test called a “SNAP” test to diagnose heartworm disease in dogs. The SNAP test is very accurate, can be performed in your veterinarian’s office using a very small amount of blood, and takes only a few minutes to complete.
How accurate is a heartworm test for dogs?
While antigen tests overwhelmingly accurate, they are not completely foolproof, as they can only detect mature heartworms, not the earlier life stages. If a dog has been infected for less than six months, the test will likely return a false-negative result. Heartworm testing in dogs is safe, highly accurate, and affordable.
What happens if a dog test positive for heartworm?
If the dog test positive on the antigen test but negative for microfilariae (Ag+/Mf-), the AHS recommends re-testing the dog with a new blood sample to confirm the diagnosis, using a different antigen test. If the second antigen test is positive, the diagnosis is confirmed, and heartworm treatment should be initiated at this point.
How much is a dog heartworm test?
A dog heartworm test typically costs $45 to $100, though this can vary by location and whether the vet performs a single test or a combination panel. A standard heartworm antigen test detects proteins from adult heartworms, while a microfilaria test checks for immature heartworms in the blood. Veterinarians often recommend both tests for a complete diagnosis, which can increase the overall cost.
What are the first signs of heartworm in dogs?
The first signs of heartworm in dogs are often subtle, including a mild, persistent cough, lethargy, and reluctance to exercise or becoming easily fatigued after moderate activity. You may also notice a loss of appetite, weight loss, or a slightly swollen abdomen. These symptoms are common and can be easily mistaken for other health issues, so it’s important to see a veterinarian for diagnosis and prevention.
Can I test my dog for heartworm at home?
How does the vet check for heartworms?