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10 Things You Need to Know About Heartworm and Your Dog

Reviewed by Dr. Melissa Beall, DVM, PhD on Thursday, September 10, 2015
Posted January 22, 2014 in Dog Diseases & Conditions A-Z

Dog Laying Down

In recent years awareness of heartworm disease has increased a great deal. Heartworm infections are virtually preventable and yet hundreds of thousands of dogs are infected every year. Preventives are safe and affordable and most of all effective. So why are we still seeing heartworm disease? There are a lot of misperceptions out there about the factors that increase the risk of heartworm infection in your pet. Let’s talk about 10 things you need to know about heartworm and your dog. Learn more about feline heartworm disease here.

1) Geographic distribution: Many people believe that heartworm infections occur only in warm humid regions like the south. Though heartworms first entered our country along the Gulf of Mexico and were once primarily found in the South, infected dogs have now been reported in all 50 states. Why? Our society is extremely mobile and when people move they take their dogs with them. Some of those dogs have heartworms.

2) Test annually: All dogs are susceptible to infection and should be tested prior to starting preventives. Additionally, all dogs -- even those on monthly prevention -- should be tested yearly for heartworms and internal parasites as part of a complete preventive health care program.

3) Heartworm reservoirs: Coyotes have been recognized as a major reservoir host for heartworms and wherever coyotes live there are likely heartworms. Additionally, un-owned stray dogs can be infected and serve as a reservoir as well.

4) Transmission of heartworms: Mosquitoes are the vector or method of transmission for heartworms. Many people are not aware of the local and regional infestations of mosquitoes that they and their dogs are exposed to. Mosquitoes transmit a vast number of diseases and mosquito control is an important step in preventing diseases. A single bite from an infected mosquito can infect your dog with heartworm.

There are many species of mosquitoes capable of transmitting heartworms and as we have learned more about mosquitoes we know that mosquitoes are not strictly a summer pest. Mosquitoes can readily overwinter in microclimates like a garage, greenhouse or other places where a warm environment can be maintained.  We know that though the risk may be greater in the summer, mosquitoes are really a year round insect that can increase in numbers quickly.

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Mike has more than 35 years of experience in companion animal veterinary practice and is a valued member of IDEXX’s Pet Health Network team since 2013.