Can a dog have heartworms? Yes, dogs can certainly get heartworms. Heartworm disease is a serious illness that affects dogs when parasitic worms live in their heart, lungs, and nearby blood vessels. These worms are spread by mosquito bites. Knowing the signs is key to early action. This guide will help you spot the signs, learn about diagnosis, and stress the importance of prevention.
Grasping Heartworm Disease in Dogs
Heartworms are not tapeworms or roundworms you see in the stool. These worms are long, thin, and look like pieces of spaghetti. They are spread by mosquitoes. A mosquito bites an infected dog, picks up baby worms (called larvae), and then bites a healthy dog, passing the infective larvae on.
Heartworm Stages in Dogs
The life cycle of the heartworm is complex and takes time to cause major damage.
- Infective Larvae (L3 stage): Mosquitoes inject these tiny larvae into your dog’s skin.
- Developmental Stage (L4 and L5): The larvae move through the dog’s tissues for several months, growing larger.
- Maturity: About six to seven months after infection, the worms travel to the pulmonary arteries (the blood vessels leading from the heart to the lungs) and mature into adult worms.
- Adult Worms: Adult worms mate, and females release offspring called microfilariae into the bloodstream. Adult worms can live for five to seven years in a dog.
The number of worms a dog has affects how sick they get. Heartworm severity in dogs ranges from mild, with only a few worms, to severe, where the heart and lungs are blocked, which can be fatal.
Spotting the Early Warning Signs
Many dogs show no signs of heartworm disease early on. This is why regular testing is so important. When symptoms do appear, they often look like other common dog illnesses. Look out for these canine heartworm symptoms, especially if you live in an area where heartworms are common.
Subtle Early Indicators
In the beginning, symptoms are minor. Your dog might seem a little tired or cough sometimes.
- Mild, Persistent Cough: This is often the first sign owners notice. It might sound dry or hacking.
- Tiredness After Mild Exercise: Your dog might not want to play fetch as long as usual or get winded quickly on walks.
- Slight Trouble Breathing: You might notice your dog panting more than normal after light activity.
Advanced Canine Heartworm Disease Symptoms
As the worms grow, they cause serious damage to the heart and lungs. The disease progresses, and symptoms become much more obvious and severe.
- Persistent Coughing: The cough becomes more frequent and severe.
- Lethargy and Fatigue: Your dog has very low energy, even when resting.
- Weight Loss: Despite eating normally, the dog loses weight because the disease affects nutrient use.
- Difficulty Breathing (Dyspnea): This is a major sign. The dog struggles to catch its breath, even when resting quietly.
- Rapid or Shallow Breathing: The breath rate increases, but the breaths are not deep.
- “Wheezing” Sound: Sometimes, you can hear a wheezing sound when your dog breathes, signaling blocked airways.
Caval Syndrome: The Worst Case
In rare but deadly cases, a large mass of worms blocks the blood flow from the vena cava (the large vein returning blood to the heart). This is called Caval Syndrome. Signs include:
- Sudden weakness or collapse.
- Pale gums.
- Vomiting blood.
- Breathing failure.
If you see any of these signs of heartworm infection in dogs, especially breathing trouble, see a vet immediately.
The Diagnostic Process: Heartworm Testing for Dogs
If you suspect your dog has heartworms based on symptoms, the next step is professional testing. You cannot reliably check dog for heartworms at home. Vets use several reliable methods to confirm the infection.
The Importance of Annual Testing
Even if your dog is on dog heartworm prevention, annual testing is crucial. Why?
- Missed Doses: Life gets busy, and a dose might be forgotten.
- Product Failure: Very rarely, preventive products might not work perfectly.
- Testing Before Starting Prevention: New puppies or adopted dogs must be tested before starting preventatives to ensure they aren’t already infected.
Types of Heartworm Testing for Dogs
Heartworm disease in dogs diagnosis relies on two main types of tests: antigen tests and antibody tests.
Antigen Tests (Detecting Worm Protein)
The most common test is the ELISA (Enzyme-Linked Immunosorbent Assay) test.
- What it looks for: This test looks for heartworm antigens. Antigens are proteins released by the adult female heartworms.
- When it works: It usually becomes positive about five to seven months after infection because it needs time for the female worms to mature enough to release antigens.
- Result Timing: Results are usually available quickly in the clinic.
Antibody Tests (Detecting the Body’s Response)
These tests are less common for primary screening but sometimes used.
- What it looks for: This test looks for antibodies the dog’s body makes in response to the larvae.
- Caveat: A positive result means the dog was exposed at some point. If the dog was successfully treated months ago, the test might still be positive for a while.
Microfilariae Test Dogs (The “Wet” Test)
This test is used after an antigen test confirms adult worms are present.
- What it looks for: This microscopic exam checks a sample of the dog’s blood for the microscopic baby worms (microfilariae) circulating in the blood.
- Purpose: Knowing if microfilariae are present helps the vet plan the treatment, as microfilariae must be cleared before or during adulticide therapy. A dog can be antigen-positive but microfilariae-negative if only males are present, or if the worm burden is very low.
| Test Type | What It Finds | When It Becomes Positive | Best Use |
|---|---|---|---|
| Antigen Test | Adult worm proteins | 5–7 months post-infection | Standard annual screening |
| Microfilariae Test | Baby worms in blood | About 8 months post-infection | Determining if treatment is needed for baby worms |
| Antibody Test | Dog’s immune response | Varies widely | Rarely used alone for diagnosis |
If the initial antigen test is positive, the vet will usually follow up with a microfilariae test and often an imaging study, like an X-ray or ultrasound, to assess the extent of the disease and determine heartworm severity in dogs.
Treatment: Addressing the Infection
Treating heartworm disease is complicated, expensive, and carries risks. It is far safer and cheaper to prevent it. However, if a dog is diagnosed, treatment aims to kill the adult worms safely.
The Treatment Protocol
The primary treatment for adult heartworms involves giving the dog special medication containing melarsomine (an arsenic-based drug).
- Stabilization: The dog must rest completely. Any hard exercise can cause dead worms to lodge in the lungs, leading to severe problems.
- Microfilariae Kill: Medications like monthly preventives are often given first to kill the circulating baby worms (microfilariae test dogs results inform this step).
- Adulticide Therapy: The main treatment involves one to three injections of melarsomine deep into the large back muscles. This drug kills the adult worms living in the heart and lungs.
- Post-Treatment Care: Strict rest is enforced for six to eight weeks after the final injection while the dead worms slowly break down and are absorbed by the dog’s body.
Risks of Treatment
The biggest risk is the body reacting to the sudden death of many worms. If a dog has severe infection (heartworm severity in dogs is high), the blockage caused by decaying worms can lead to severe pulmonary inflammation, blood clots, or even death. This is why low-worm burden dogs tolerate treatment much better than heavily infected dogs.
Prevention is the Best Defense
Because diagnosis and treatment are difficult and risky, the focus must always be on prevention. Dog heartworm prevention is simple, safe, and highly effective when done correctly.
Monthly Preventatives
The most common way to prevent heartworms is through monthly medication. These medications kill the infective larvae shortly after a mosquito bites the dog, before they can mature into adults.
These products often come in chewable tablets, topical liquids applied to the skin, or injectables given by the vet. They must be given year-round, without missing a dose.
Year-Round Protection
Heartworms are an issue any time mosquitoes are active. In warm climates, this can be year-round. Even in areas with cold winters, a single warm spell can allow mosquitoes to thrive and transmit the infection. Therefore, consistency is key for effective dog heartworm prevention.
Injectable Prevention
For owners who struggle with monthly dosing, there is an injectable option (Moxidectin). This is given by a veterinarian every six or twelve months, depending on the product, offering long-lasting protection after the initial testing confirms the dog is negative.
Frequently Asked Questions (FAQ)
Can I tell if my dog has heartworms just by looking at them?
No. Early canine heartworm symptoms are very subtle. By the time symptoms are obvious, the infection is advanced. You must rely on testing, not just observation, to be sure.
How long does it take for a dog to show signs of heartworms?
It takes at least five to seven months for a dog to start showing signs because the worms need that long to mature into adults capable of causing damage. Often, signs do not appear until the disease is advanced.
Is heartworm disease contagious from one dog to another?
No. Heartworms are only spread through the bite of an infected mosquito. You cannot catch heartworms from an infected dog by sharing bowls or playing closely.
If my dog coughs once, does that mean it has heartworms?
A single cough is usually not a sign of heartworms; it could be kennel cough or allergies. However, if the cough is persistent, dry, and happens after exercise, it warrants a vet visit for heartworm testing for dogs.
What is the prognosis for a dog treated for heartworms?
If the infection is mild to moderate, the prognosis after successful treatment is generally very good, provided the dog adheres strictly to the required rest period. If the dog had severe infection (heartworm severity in dogs was high), long-term complications like permanent lung damage are possible, requiring lifelong careful monitoring.