Nibbles and Bits - June 2009

It’s finally nice to see blue sky and no more frost. We don’t have to worry about covering the tender new plants in the garden anymore and thoughts of summer vacation are becoming more of a reality. With the warm weather, however, come some unwelcome pests- namely mosquitoes.

You may think of these little insects as a mere annoyance, causing itchy bumps on your arms and legs, but to your pets, they could potentially be deadly. Mosquitoes can carry a tiny larval form of a parasite called dirofilaria immitis, which causes heartworm disease.

Heartworm is a disease of dogs and can also affect cats. Your pet does not need to come into contact with other animals to get it since it is transferred by mosquitoes. Even if your pet is rarely outside, the mosquitoes can still get into the house and bite. When a mosquito bites, it injects some of the baby heartworms, called microfilariae, into the pet’s skin. They eventually migrate to the heart and the blood vessels leading from the heart to the lungs over the course of about 5 months. At their adult size, they are 4-8 inches long. In dogs, they cause coughing, exercise intolerance and can be fatal if not treated. In cats, they can cause vomiting or signs of asthma, but in some cases, the only sign is sudden death.

Heartworm disease in dogs is treatable with a medication called immiticide which is an arsenic-containing drug. It is injected into the muscles of the back in the hospital and then the dog is sent home on strict rest for one month. This is because when the adult heartworms die, they can break apart and cause blood clots (or thromboemboli) in the lungs which can be fatal. Keeping the dog as quiet as possible after treatment can help prevent this. In cats, there is no treatment for killing the heartworms. Immiticide is not considered safe for cats, so the treatment involves controlling the signs with drugs such as cortisone until the worms die on their own in two to four years. In dogs, which are the parasite’s natural host, they can live for five to seven years.

The good news is that heartworm disease is completely preventable. We start new puppies right away on heartworm preventative and this is continued for life. For adult dogs that are not currently on heartworm preventative, they need to be tested for heartworm before starting the preventative. This can be done with a simple blood test that we send out to our local lab and we get results the next day. We highly recommend running the heartworm test in combination with the test for lyme disease. That test is done right in the office so we have results in a few minutes. Retesting should be done every one to two years thereafter. Heartworm is more difficult to diagnose in cats. They do not always turn positive on the test as reliably as dogs so discovering it can be a challenge. Heartworm preventative is very easy to give- just a chewable tablet or topical liquid once a month. There are three products we use- Heartguard, Interceptor and Revolution. The best choice for you and your pet is something we can discuss with you during the exam.

If you would like to learn more about heartworm disease, please visit our display at the hospital through the month of June. We have some free things to give away, games for the kids, and if you pass our quiz, you’ll be entered in a drawing to win a six-month supply of Heartguard. So stop by and good luck!