Heartworm Disease & Control in Dogs

Heartworm disease is prevalent in dogs worldwide. Because heartworm disease has such
serious and fatal consequences, it is essential that every dog be on year round heartworm
prevention.

Heartworm Disease

Heartworm disease is caused by the worm, Dirofilaria immitis, which can infect the heart
and lungs causing severe and fatal disease. Heartworms are spread to dogs by mosquitos
that have bitten other infected animals with heartworm disease. In the early stages of
heartworm disease, there are no clinical signs of infection. Unfortunately, it is not until the
late stages of disease when the heartworms have multiplied, blocked and damaged the
heart, blood vessels and other organs that symptoms become apparent. It may take up to
two years before a dog will start showing signs of heartworm disease.
Signs of Heartworm Disease
• Shortness of Breath
• Coughing (especially after exercise)
• Exercise Intolerance
• Lethargy
• Weakness
• Weightloss

Treatment of Heartworm Disease

Although treatment of heartworm disease can be risky, heartworm disease is inevitably
fatal without treatment. Heartworm positive dogs require intensive veterinary care and
monitoring at a veterinary hospital. Response to treatment is usually related to degree of
heartworm infection. A veterinarian will be able to perform blood tests and other diagnostic
tests to estimate prognosis.

Heartworm Prevention

Regular heartworm prevention far outweighs the risks associated with contracting
heartworm disease in dogs. If used correctly, heartworm preventatives are nearly 100%
effective in preventing heartworm disease. There are many forms of heartworm
preventative products available in the form of chews, tablets, top spots and injections.
Prevention should be used for the rest of your dogʼs life.
If you have acquired a new dog and are unsure of your dogʼs heartworm status or you
have a missed a dose of heartworm prevention, please consult with your veterinarian
before starting heartworm preventatives. A special blood test may be required to check for
heartworm infection.

Monthly Tablets & Chews

There are may flavoured monthly chews and tablets available over the counter. These
should be administered around the same time each month. Be sure to use a heartworm
preventative that is specific to your dogʼs weight. Otherwise, underdosing may result in
inadequate protection. Try to be consistent with the heartworm preventative brands that
you use. Many heartworm tablets and chews also help to prevent intestinal worms.

Daily Tablets

There are also daily heartworm preventative tablets, but these must be given everyday for
adequate protection. While the mainstay of treatment many years ago, it has fallen out of
favour with advent of monthly heartworm preventatives being more convenient for dog
owners.

Monthly Top Spots

For some dogs, especially those who are fussy or difficult to medicate, a monthly top spot
applied to the nape of the neck may be a more feasible option for some dog owners.
Similar to the tablets and chews, monthly top spots should be applied around the same
time each month. Consistency among brands and using a product appropriate to your
dogʼs weight is also important. Top spots for heartworm prevention have also gained
popularity because many of them have dual action against intestinal parasites and fleas.

Yearly Injections

Giving heartworm preventitives everyday or monthly may be impractical for some dog
owners and yearly heartworm injections administered by a veterinarian may be a better
alternative for some owners and their dogs. Yearly injections last one whole year and
should be repeated the same time every year. Yearly injections prevent heartworms only.
Regardless of which heartworm preventative you select to treat your dog, treatment should
be lifelong to prevent potentially fatal heartworm disease