Puppies may develop a common condition known as heartworm disease, or CHWD. This condition occurs in areas all over the world, and is caused by the Dirofilaria immitis worm. This worm is a parasite that lives in the blood vessels that attach the heart and the lungs, known as the pulmonary arteries. Heartworm disease is most common in tropical climates where mosquitoes are abundant, because heartworm is spread though contact with infected mosquitoes. Puppies with heartworm may only display symptoms in very severe infestations. This means that if puppies are showing symptoms of heartworm, the disease is quite advanced.
The presence of heartworm in a puppy's body causes inflammatory changes in the lungs. This inflammation, combined with the pressure from an enlarged heart on the puppy's windpipe, causes a severe cough, which is often worse when the puppy is lying down. This cough may be dry or moist, and is often accompanied by blood, known as hemoptysis. Coughing in puppies with heartworm indicates an advanced stage of the disease.
Puppies infected with heartworm often exhibit labored breathing, especially upon exertion. This may occur during or after bouts of severe coughing. Puppies that suffer from this condition often refuse to run or play, as the energy and oxygen that exercise requires can make breathing more difficult.
Congestive Heart Failure
Heartworm symptoms often do not surface until the heart is damaged. According to Pet Place, heartworm disease is a debilitating illness that leads to death, if left untreated. Symptoms of congestive heart failure may develop in infected puppies. These symptoms include heavy breathing, pulsing jugular veins in the neck upon standing or sitting and an accumulation of fluid in the abdomen.