Canine & Feline heartworm disease develops when a dog or cat is bitten by a mosquito carrying microscopic larvae of a parasite called Dirofilaria immitis. As a mosquito feeds, these larvae quickly enter the dog or cat’s bloodstream where they migrate into the heart and lungs and grow into adult worms. Undiagnosed and severe infection often leads to heart/lung disease and death. Even indoor cats and dogs are at risk of infection because mosquitoes are often found inside homes and some indoor pets go outside for short periods. Although easy to prevent, heartworm disease continues to be a major health problem throughout the United States and wherever mosquitoes live. If you ever see or get bitten by mosquitoes, your pet is at risk!