Bellevue Veterinary Hospital, Parksville

(250) 248-2031

Heartworm disease

heartwormVeterinarians will often ask pet owners whether they have done, or will do, any travelling with their pet, and if so, where to, & what times of the year. Part of the reasoning behind asking these questions is to assess the pet's risk for contracting heartworm disease. This parasite infestation is easy to prevent, but very difficult (expensive and risky) to treat. As always, we'd much rather prevent this.

Heartworm disease is the infestation by a worm that develops in the bloodstream of the dog and eventually matures to the adult form that lives in the vessels of the lungs and in the heart. For obvious reasons, this infestation can be a serious health threat to the patient.

This parasite is transmitted through a mosquito bite during hot weather in some areas of North America (and other areas of the world). These geographical areas of concern (known as endemic areas) tend to be hot and humid during an extended period of time in the summer months. Such areas identified in Canada are parts of Southern Manitoba, Southern Ontario, and the Okanagan Valley in B.C. The Eastern & Southern States are endemic for heartworm disease as well (highest risk in Southeastern states such as Florida). These places are considered to have risk for the transmission of the heartworm parasite (Dirofilaria immitis) from mosquito bites.

Prevention of this parasite is quite simple. The two products we use for prevention of Heartworm Disease are discussed below. 

1. Interceptor® or Sentinel® - This is a pill that is given once each month during the exposure time to cover the period of possible exposure. If the dog has possibly been exposed previous to treatment, a heartworm test should be performed (simple, quick blood test) before starting this medication.  There is the exception of those under 5 months of age, because they aren't old enough yet to have a full infestation. This monthly medication also treats the dog for many intestinal worms that may occur in our own region any time of the year.

Sentinel® is a combination of Intercepter and Program (a flea preventative) and is handy for dealing with fleas, worms and heartworm prevention. This pill is beef flavored and easy to give to dogs.

2. Revolution® - This is a liquid solution applied to the skin on the dog's (or cat's) back. This medication is absorbed through the skin and lasts for a month at a time to prevent heartworm (and fleas!) in dogs and treat internal & external parasites in cats as well.

The advantages of using Revolution® are as follows. It is the only product available that is also approved for use in cats and it is very effective against fleas in both species. It also discourages some intestinal parasites and kills ear mites. We don't have to test for heartworm in order to use this product and it can be used just once whenever it is needed -- if for example you only plan to visit the Okanagan for a couple of weeks, one dose of Revolution would be sufficient to prevent Heartworm infection.

Even when heartworm testing is not absolutely necessary for a veterinarian to prescribe one of the above medications, it is still recommended at regular intervals (every 3 years, for example) if you travel to endemic areas regularly with your pet. The only way we'll ever know if heartworm incidence is changing in our area is to test our dogs with some regularity. The frequency of testing recommended will depend on each individual's risk of exposure (and the incidence reported by other veterinary experts - published regularly).

Heartworm is a complicated parasite. As far as we can tell at this point, Vancouver Island is not a geographical area of concern with regards to the transmission of this worm via mosquitoes. However, we are all keeping our eyes and ears open for any changes that may occur. Considering climate changes that are suspected, heartworm disease may become a larger risk in more and more areas of North America and elsewhere over time.

Heartworm disease is:

  • transmitted by mosquitoes during hot weather 
  • easy to prevent; very difficult to treat & with life threatening side-effects
  • geographical incidence in hot, humid places during extended hot season(s)
  • Southeastern Canada & Okanagan Valley, BC plus Southern & Eastern U.S.A.

Easy Safe Prevention:

  1. once/month pill
  2. an application to the skin once/month

Ask your veterinarian about your pet's risk if you suspect any likelihood.

Tags: Travel, Parasites, Medications