Heartworm Disease in Dogs
What is Heartworm Disease?
Heartworm disease is a potentially fatal disease caused be the blood-borne parasite Dirofilaria immitis and contracted through mosquito bites. The adult parasites (worms) are found in the heart and adjacent large blood vessels, even spilling over into the lungs. Theses worms cause a blockage to blood flow and eventually cause congestive heart failure and, if untreated, death.
How do Heartworms get into the heart?
Adult heartworms living in a dog’s heart and pulmonary arteries produce millions of offspring called microfilaria. These microfilariae live mainly in the bloodstream’s small vessels. To complete their life cycle, the microfilaria must enter a mosquito. This happens when the mosquito feeds on an infected dog. After developing in the mosquito for 10-30 days, they move to the mosquito’s mouthparts as an “infective larvae”. They will then pass into the next individual the mosquito feeds on. If this is a dog they can then pass through more life stages growing to maturity.
All dogs are susceptible to mosquitoes. Long hair and living indoors does NOT prevent a dog from getting heartworms.
What do Heartworms do to the dog?
Adult heartworms cause disease by clogging the heart and major blood vessels leading from the heart. This clogging reduces the blood supply to other organs of the body, particularly blood flow to the lungs, liver, and kidneys leading to malfunction of these organs. Unfortunately, it can take several years before infected dogs show clinical signs and by this time the disease is well advanced.
The most obvious signs of disease are a dry cough, shortness of breath, weakness, and loss of stamina. These signs are most noticeable following exercise, and some dogs may even faint. In advanced cases, congestive heart failure may be apparent and the abdomen and legs will swell from fluid accumulation.
Microfilaria (young produced by the adult heartworms) circulate throughout the body. Because they are as wide as the small blood vessels, they may block blood flow in these vessels. The body cells being supplies by these vessels are then deprived of the oxygen and nutrients they need. In the lungs, destruction of tissue leads to coughing. In the liver, cirrhosis occurs causing jaundice, anemia, and general weakness. Poisons can accumulate in the body when the vessels of the kidney are obstructed.
How is Heartworm Infection diagnosed?
A blood test requiring only a few drops of blood can be run in the hospital in a manner of a few minutes to determine if a dog is harboring adult heartworms. A very occasional false negative test can occur because dogs with less than five adult heartworms will not have enough antigen to test positive. An even more rare cause of a false negative is if only male heart worms are present in the dog.
What happens if my dog has heartworms?
The course of treatment will depend on the severity of disease. This will be assessed with chest X-rays and bloodwork, and possibly other diagnostic tests. From the results of these tests a specific treatment plan will be developed for your dog.
How can I prevent my dog from getting Heartworms?
The best thing about heartworm disease is that it is preventable! We have several different products available that keep any infective larvae that passes into your dog from a mosquito bite from maturing into adult heartworms. These products range from an injection that lasts for 6 months to flavored tablets taken every 30 days.