Heartworm survivors face hard recovery

Heartworms are spread through the bite of a mosquito and there are some 20 species that can carry and spread the disease.

Irrigation and population growth in the West has expanded the habitat for both the Western Knot Hole and the Asian Tiger mosquitoes. The former is the primary vector in the West and the latter is able to live and reproduce in very small containers such as flower pots.

After an infected mosquito bites your pet, the larvae or “microfilaria” make their way into the tissues. Within 3–12 days the larvae molt into a juvenile adult and find their way to the blood vessels in and around the heart. Another 6–9 months are required for mature adults to develop.

Adult heartworms can grow to 12 inches long and infections can range from as few as one to as many as several hundred worms living within the pulmonary vessels and right atrium of the heart. Their presence can cause chronic inflammation within the lungs and lining of the heart, leading to scarring, asthma, coughing, exercise intolerance, heart failure and sudden death.

While heartworm disease can be effectively treated, the damage done within the heart and lungs is often irreversible. Treatment is also expensive and requires strict cage confinement for 2–3 months.

Therefore, sticking to monthly preventives year round, or using the 6 month injectable product, is the best ways to ensure your pets protection.

Yearly testing requirements are simply because the monthly preventives are effective only at eliminating the larvae. Once the larvae have developed into the juvenile adults, the preventive is no longer effective. So the test looks for the presence of adult worms that may have developed because of a missed dose, missed timing of dosing or ineffective medication.

Heartworms actually can be contracted during winter months. While it is true that maturation of the larvae within the mosquito comes to a stop below 57 degrees, development quickly resumes once the temperature rises. And, as mentioned previously, some mosquitoes can reproduce in very small “microenvironments” around our homes that may be quite a bit warmer than the air temperature around them. So recommending when to stop and start giving preventative is just a guess at best.

Heartworm larvae have been found inside of mosquitoes in the dead of winter and at elevations as high as 8,000 feet.

Heartworm infections are not limited to our domestic dogs either. Wild canids such as coyotes continue to be a reservoir for infection in suburban and rural areas such as ours.

Cats and ferrets also are susceptible to the disease and your veterinarian can recommend the best options for those pets.

The current recommendations are to start prevention during your puppy’s first visit at about 8–12 weeks of age (6 months with the injection). A simple 10 minute blood test is then performed after 6 months of age and then yearly or as recommended by your veterinarian. Starting an older dog on prevention requires a test prior to starting medications followed by a second test 6–9 months later.

Many heartworm preventives also are effective against intestinal parasites, giving your pet added protection. The six month injectable, given by your veterinarian, is nice because it lets you “get it and forget about it.” While recommendations may vary slightly, it is best to talk to your veterinarian to determine the right product and options for your pet.

Drs. Tom and Tara Suplizio own Animal Medical Clinic in Grand Junction. The Suplizios are graduates of the Colorado State University Veterinary School. Email them at .(JavaScript must be enabled to view this email address).


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