Basic Facts 

   Heartworm disease is a serious and potentially fatal parasitic disease that primarily affects dogs, cats and ferrets. Heartworm disease is becoming increasingly more common. Several cases are diagnosed each week. The heartworm lives primarily in the right side of the heart, and in the nearby large blood vessels. The female worms produce large numbers of immature heartworms which circulate in the blood. 
   The microfilaria, “baby heartworms,” are ingested by a mosquito biting an infected animal. After living in the mosquito and developing in its digestive tract for 1-2 weeks, the microfilaria are spread to another animal when the mosquito bites again. Larvae migrate under the skin for several months, before going into the blood vessels in the lungs. Once in the dog’s heart and lungs, they mature and reproduce, releasing more larva into the bloodstream. It takes about six months for the heartworm to reach adulthood after infecting the dog. Heartworms will continue to grow and will injure the blood vessels, resulting in severe lung and heart disease.
   The important thing for dog owners to remember is that a great deal of damage can occur before any obvious signs are noticed. Delayed treatment may result in heart failure and/or permanent damage to the liver, lungs, and kidneys – with eventual death. The signs of heartworm disease which you are most likely to notice include coughing, sluggishness, loss of appetite, rapid tiring, sudden swelling of the abdomen and labored breathing. Signs of possible heartworm infection in cats include coughing, respiratory distress, and vomiting.
   Diagnosis is made by finding the microfilaria in a blood sample. It will be six or seven months after exposure before microfilaria can be detected in the blood. Because of this, heartworm tests should be done annually. The diagnosis of a heartworm-infected cat is more difficuly than with dogs and a series of blood tests is needed.
   There obviously is no way to keep your dog from being bitten by mosquitoes, but preventative medications are available for both cats and dogs. A heartworm preventative must be given to dogs which destroys the “baby heartworms” before they have time to migrate through the body and grow up in the heart of your dog. Protecting your pet from heartworm infection is as easy as a visit to your veterinarian, who can provide you with a preventative medication to help keep your dog healthy. In the southeastern United States, we recommend that medication be given all year long since our mosquito season is quite variable.

Did you know... 
* Of the 150 species of mosquitoes in the United States, two-fifths may transmit the disease. 
* Adult heartworms can reach one foot in length. 
* Heartworm positive dogs often have 15 to 19 worms living in their heart and lungs. 
* In extreme cases, dogs may have up to 250 heartworms at once. 
* Heartworm positive cats usually only carry 1 to 3 heartworms. 
* It only takes 1 heartworm to kill a cat. 
* Approximately 50 percent of dogs and 5 percent of cats are currently on a heartworm preventive.