It is June 1st … have you started your dog on their heartworm prevention for the summer? Today is a great day to remind ourselves why all dogs should be tested for heartworm exposure every spring and protected against Heartworm Disease every summer. Many of our clients will have seen the poster of a heartworm infected heart in our exam room, and it is a very meaningful picture.
Heartworm Disease is a serious and potentially life-threatening condition caused by parasitic worms that migrate to the heart and surrounding blood vessels. Our pets contract this disease from mosquitoes that are infected with heartworm larvae. When an infected mosquito bites a dog, the heartworm larvae are injected into the skin, where their eventually find their way to the heart and lungs where they mature into adults, and begin to reproduce. The worms can grow to a length of 15-30 centimetres each and as their numbers increase they begin to occlude the pulmonary artery and eventually the chambers of the heart (in severe cases a dog may be infested with hundreds of worms).
The worms decrease the ability for the heart to pump blood and deliver oxygen to the vital organs. The presence of the worms also creates a significant inflammatory response, causing permanent scarring of the heart and surrounding tissues. Left untreated, heartworm disease is fatal. Mature worms also produce thousands of larvae that can then be spread to other dogs or cats by mosquitoes. Dogs are extremely susceptible to heartworm disease, and nearly 100% of dogs exposed to larvae become infected.
Southern Ontario is known as a “high-risk” area for heartworm in Canada, along with southern Quebec, Manitoba & the Okanagan Valley. The most recent study on “Heartworm in dogs in Canada” published in 2010 by the Ontario Veterinary College at the University of Guelph revealed a 60 per cent increase in the number of dogs in Ontario with heartworm since the last study of its kind was conducted in 2002. The study showed that 564 dogs tested positive for heartworm in Canada in 2010 and over 75% of those dogs were located in Ontario (431 dogs). The study also showed that eighty per cent of animals that were found to have heartworm had not been on a heartworm preventive medication. In a few cases, however, pets that had been receiving heartworm preventive medication also tested positive for the disease; the most common reason for this was that the pet owners indicated they had forgotten to give their pet the preventive medication at the prescribed intervals.
The American Heartworm Society recommends annual testing and preventive medication for dogs that live in heartworm prevalent areas of the country (more information can be found here: http://www.heartwormsociety.org/veterinary-resources/canine-guidelines.html). Heartworm Disease is found in Ontario… Heartworm Disease can kill your dog. Please remember to use your dog’s preventive medication each and every month!