By Dr. Jeff Steen Medical Director Alameda East Veterinary Hospital www.alamedaeast.com
As warmer weather arrives, so do mosquitoes. Not only are mosquitoes annoying but they can also transmit heartworms to your four-legged companion. This infection is completely preventable; yet, every year thousands of dogs become infected and many lose their lives to this deadly parasite.
Dogs are the definitive host for heartworms. Infection occurs when microscopic larvae are injected into a dog by a mosquito during a feeding. These larvae grow and migrate from the skin into the blood vessels and eventually into the heart and pulmonary arteries. After 5 or 6 months they become adults and can grow as long as 14 inches. In severe cases dogs can have more than 200 adult heartworms in their hearts and pulmonary arteries.
Prevalence rates of heartworm vary across the United States depending on the regional climate, the number of heartworm infected dogs in the population and exposure to mosquitoes. In some endemic regions up to half of all dogs not on preventative care are heartworm positive. It is best to ask your veterinarian about testing and prevention guideline for your specific region. If you travel extensively with your pets, it is best to use a preventative year round.
The most common clinical signs of heartworm disease include coughing, exercise intolerance and difficulty breathing. Dogs with higher numbers of worms are more likely to show clinical signs of disease. If dogs only have a few heartworms they may not show any clinical signs, but can still act as reservoirs to spread the disease to other dogs.
Heartworm disease is treatable if the infection is not severe. Treatment involves injections of a drug called Melarsomine (Immiticide ®). There are many potentially severe side effects when treating a heartworm positive dog, some of which can be fatal. The cost to treat heartworm disease can easily run into the thousands, especially in severely infected dogs. Prevention is much safer and significantly less expensive.
There are many safe and effective heartworm preventatives available including ivermectin (Heartgard ®, Heartgard Plus ®, Iverhart Plus ® Iverhart Max ® and Trihart Plus ®), milbemycin (Interceptor ® and Sentinel ®), selamectin (Revolution ®) and moxidectin (Advantage Multi ® and Proheart6 ®). Testing for heartworms is recommended before starting a preventative since serious side effects may occur if a dog suffering from heartworm is started on a preventative. Most heartworm preventatives also prevent common intestinal parasites such as roundworms, hookworms and whipworms.
The American Heartworm Society recommends year round prevention for all dogs in the United States. The main reason for this recommendation is compliance, as many pet owners simply forget to start heartworm preventative in the spring. Another good reason to use preventatives year round is to prevent intestinal parasites, which are not seasonal and are very common in most parts of the country.
If you need a mosquito repellant for your dog, you want to chose one containing permethrin. Several products are available specifically for dogs including Advantix and Proticall. They will repel mosquitoes and ticks for four weeks. It is best to avoid any DEET containing insect repellants since dogs, prone to licking themselves, are very sensitive to oral ingestion of DEET. You can apply DEET-free insect repellants marketed for children, but be sure to avoid contact with eyes, noses and mouths.
If your dog is not currently on heartworm prevention, contact your veterinarian about testing and preventative guidelines. And then get outdoors and enjoy the summer!
