Heartworm disease is caused by a blood parasite called Dirofilaria immitus. Dogs are infected when they are bitten by a mosquito that is carrying immature worms called larvae. The worms live inside the heart and surrounding blood vessels and feed off nutrients in the blood. They can grow as long as 15-30cm and in severe cases, a dog may be infected with hundreds of worms. The heartworms cause damage to the heart muscle and block the blood flow from the heart. When damage is severe death may result.
What are the Signs of Heartworm Disease?
In the early stages, dogs often have no clinical signs, especially when they have only a small number of worms in their heart. As the disease progresses, clinical signs become more noticeable and include reluctance to exercise, weakness, coughing and trouble breathing. In advanced cases dogs will develop congestive heart failure. Dogs in congestive heart failure lose weight, have a poor body condition, breath rapidly or with difficulty and develop a buildup of fluid within the abdomen.