What is heartworm disease?

This is a parasite that infects dogs in its larval (immature) form through a mosquito bite.  The larvae travel through your dog’s bloodstream and will ultimately settle in your dog’s heart.  They can grow up to 30 cm (12”) in length, so they can take up quite a bit of space in your dog’s heart.

Heartworms reproduce after the larvae mature into adults in the heart. These adults create immature forms that circulate through the dog’s bloodstream, that are then picked up by mosquitos when your dog is bitten.  The cycle repeats!

Heartworm disease is serious, as it can be fatal if it’s not caught in time and treated.  

What are the signs of heartworm disease?

Some of the most common signs of heartworm disease include:

  • Weight loss
  • Fever
  • Low energy
  • Coughing

These signs are not specific for heartworm disease only. If your dog has been in an area where they can acquire this infection (especially if not treated with preventative medication), then testing your dog is the best way to determine its presence. Many dogs will be asymptomatic despite being infected with heartworms, making testing of at-risk dogs even more important.

What kind of problems can heartworms cause?

As mentioned above, not all dogs will show symptoms of heartworms.  Some can carry them around inside for years without anyone being any wiser!  However, that doesn’t mean that they aren’t causing a problem.  Heartworms can cause serious, even fatal problems, including heart problems, kidney problems, lung problems, and liver problems.

How is heartworm disease treated in pets?

There are two types of heartworm disease treatment available for pets.  These are:

  • Preventative care
  • Diagnostic care

Preventative care would be through regular check-ups with your vet and having your dog tested regularly for heartworm.  Since it can be a minimum of 6 months for most dogs to start showing symptoms, getting a regular check-up with heartworm testing can gain months of treatment time if they do test positive.

If you have the option of choosing a care method, preventative is definitely the way to go.  Preventing a condition before it starts is always your best method of attack.

As you can guess, diagnostic care is after the heartworm has “moved in” and settled down in your dog.  The diagnosis could be, best-case scenario, while the larvae are still making their way to the heart.  Your vet will be able to prescribe a de-wormer to help kill and flush out the parasites.

Diagnostic care often takes place after you, as a pet parent, notice the symptoms mentioned above and bring your dog in for care.  This care is going to often take the form of several potent deworming treatments and regular check-ups to see how they are progressing.

In some cases, a severe worm infestation can cause serious complications with those major organs.  These can be treated, too, but it isn’t always successful.  The longer it goes unchecked and uncared for, the more serious it gets.  It can be fatal in some cases, especially if your pet is still growing.  

Keeping your pet safe from heartworm

It’s possible for any pet to pick up heartworm in many areas in Canada, but you’ll find most cases in the warmer climates since larvae prefer warmth.  For example, southern Ontario and British Columbia, among others.

If you want to keep your pet as safe as possible, some tips include:

  • Discussing with your veterinarian prior to travel whether your pet should be on a heart worm preventative
  • Following recommendations for heartworm preventative treatment as they must be given according to recommendations to be effective. 
  • Don’t skip regular check-ups.
  • If there is a problem, treat it as quickly as possible

The goal is just to understand where the risks are, and discussing with your veterinarian what you can do to keep your pet as safe as possible from acquiring heartworm disease. 




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