St Lawrence Veterinary Services

It’s heartworm and tick season again!
Is your dog protected?

Heartworm:

The scientific name of “heartworm” is Dirofilaria immitis. Heartworm is endemic in Ontario, becoming more prevalent the farther south you travel. The parasite is transmitted only by mosquitoes. It takes at least 6 months from the time of exposure before an active infection develops. The adult worms lodge themselves in the heart and large pulmonary vessels.

Heartworm infection is a very serious disease. Infected dogs will show signs of cardiac disease: coughing, exercise intolerance, fatigue, panting, weight loss, decrease in appetite, and sometimes sudden death.

Treatment does exist for heartworm positive dogs, but it is expensive and does not come without significant side effects.

Because this disease can have devastating effects on your dog, and can sometimes be fatal, we strongly recommend heartworm prevention each summer.

Prevention starts with a blood test to ensure your dog is not already carrying heartworm (the test also screens for exposure to Lyme disease). As part of a heartworm surveillance program, we recommend heartworm testing every other year.

There are many forms of heartworm preventative medications. The “old standby” for heartworm prevention are chewable tablets. However, we often recommend a topical liquid which also help control many other parasites such as fleas, mange mites, ear mites, intestinal worms, and ticks. These medications are given once per month from June to November each year. If you travel south during the winter months (e.g. to Florida) with your canine friend, mosquitoes will be present so it is important to consider heartworm prevention before heading on your trip.

Ticks:

Ticks are an ever-increasingly common type of arachnid external parasite. They have a distinct body and eight legs, and their favorite natural habitats include: edges of grassy fields, low-lying underbrush, and urban areas, especially if deer are present.

We have many different canine tick-control products, which include topical liquids and tick collars. Many tick control products can be very dangerous, or even fatal to cats – so their use around cats must be with the utmost level of caution.

Common species of ticks in our area:
a) The Groundhog Tick, Ixodes cookie - this species of tick will attached and feed, but is not known to transmit disease
b) The American Dog Tick, Dermacentor variabilis – the preferred host of the adult tick is the dog. This species of tick can transmit Rocky Mountain spotted fever, and can cause “tick paralysis”.
c) The Deer Tick (aka The Blacklegged Tick), Ixodes scapularis – adults prefer to feed on white-tailed deer, but all life-stages of the tick will feed on dogs and humans. The Deer Tick is the most important vector for the transmission of Lyme disease.
d) The Brown Dog Tick, Rhipicephalus sanguineus – is becoming more and more common in Eastern Ontario. This species of tick can live inside dwellings, or dog kennels.

There are two “blooms” in the tick population each year, occurring in the early spring and late fall. During these times, tick bites will be most common. Tick bites are usually not painful, but cause irritation (reddening) of the skin, and minor swelling. Even after the tick has been removed (or falls off), swelling and/or redness in the area of the bite can last for a few weeks.

Lyme disease is caused by the bacterium Borrelia burgdorferi. In dogs, the first symptoms of Lyme disease may start 4-6 weeks after a tick bite. They most commonly include: fever, fatigue, lameness, or joint swelling. We recommend any dog showing these signs be tested for Lyme disease.

Prevention of Lyme disease is multi-factorial. First, tick control products will help repel or kill ticks before they attach, or cause them to die and fall off shortly after attaching. Second, daily “tick checks” done by the owner will help identify and remove ticks. Third, a vaccine is available for canine Lyme disease. We use a recombinant DNA, non-adjuvanted vaccine for Lyme disease. The vaccine works by targeting an outer surface protein which the Lyme bacteria uses to inject itself from the tick into the dog.

An easy environmental control measure involves lining the perimeter of your backyard with a border of cedar wood chips at least 8 inches wide – it is believed ticks won’t cross over this “barrier”.

Please do not hesitate to contact us if you have any questions about these diseases.
At St.Lawrence Veterinary Services preventative medicine is very important to us, and we strive to help keep your dog healthy so you can enjoy the summer!

Links:

http://www.heartwormsociety.org/article_21.html - American Heartworm Society

http://www.uoguelph.ca/pdc/Factsheets/Other/Ticks.htm - University of Guelph (tick info)

http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=1588 – more about Lyme disease

http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=615 – more about heartworm