April is Heartworm Awareness Month. A heartworm is a parasitic worm (Dirofilaria immitis) that lives in the heart and pulmonary arteries of an infected animal. The worms travel through the bloodstream – harming arteries and vital organs as they go – ultimately completing their journey to the vessels of the lung and the heart chamber about six months after the initial infection. Several hundred worms can live in one dog for five to seven years. Heartworm disease is serious and can be fatal.
Take shelter pup, Ernie, for example. This 4-year-old Terrier mix was taken to Southwest Florida Veterinary Specialists where he was diagnosed with an advanced case of heartworm disease, called Caval syndrome. Caval syndrome typically occurs with a severe infection and the worms relocate to the right side of the heart, causing abnormal blood flow and restricted valve function. This condition can be fatal if the worms are not removed.
Dr. Arsenault used a device through the vein in Ernie’s neck to remove all of the heartworms in his heart. Ernie did excellent for his procedure and returned to Humane Society Naples the following day to get ready for adoption. Ernie remains on medical treatment to kill the remaining worms that live in his lungs.
A total of 19 worms were in this little guy’s heart. Each worm was approximately 10 inches in length! Those are 19 reasons to use heartworm prevention.
What is heartworm disease?
Heartworm disease is caused by a parasite called Dirofilaria immitis. While primarily a problem in dogs, cats, and ferrets, it infects many other mammals including bear, fox, and wolves. This parasite, when mature, can number in the dozens within the dog. The parasites cause severe inflammation in the blood vessels and lungs, resulting in the destruction of blood cells, exercise intolerance, cough, and even heart failure.
How do dogs get heartworm disease?
Heartworm disease is transmitted via the bite of infected mosquitos. While the mosquito takes a bloodmeal from an infected dog, microscopic larvae called microfilaria are ingested where they mature. When the mosquito bites another dog, the larvae migrate down the mouthparts and into the dog’s blood. They migrate through the body for 5-7 months while they mature. Adults then reside in the blood vessels that go from the heart to the lungs (the pulmonary arteries).
Is it contagious?
Because heartworm is transmitted by mosquitos, it is not contagious via dog to dog contact. However, if your dog is in the area of a heartworm positive dog, it is more likely to get infected due to being exposed to the same population of mosquitos.
My dog isn’t showing any symptoms of heartworm disease, do they require treatment?
Yes! Most dogs that are infected do not show any outward signs. However, the worms are causing severe damage to the blood vessels and lungs every day.
Why is the treatment period so long?
The 9-month treatment protocol we perform is set forth by the American Heartworm Society. It has been designed to be maximally effective while decreasing complications.
Does treatment have any complications?
Yes, rarely. Most complications are not caused by treatment, but from chronic heartworm disease itself. The most common complications or clinical signs associated with heartworm disease, which can occur during any time of treatment include but are not limited to, cough, exercise intolerance, vomiting, difficulty breathing, coughing blood, and thromboses (blood clots).
Do I really need to keep my dog’s activity restricted the whole time?
Yes! Decreasing activity will keep blood pressure and lung pressure down. While the worms are dying, they are more likely to be pushed too deep into the lungs, or even elsewhere in the body. This can have significant, and even fatal, consequences.
What do I do if I think my dog is having complications of heartworm disease or heartworm treatment?
If it is during regular business hours, please call us! Our veterinary staff will help guide you on whether it is an emergency. If it is after hours, please contact any local emergency clinic. Local clinics include Animal Specialty Hospital, Southwest Florida Veterinary Specialists, Specialized Veterinary Services, Florida Veterinary Referral Center and Emergency Pet Hospital.
How do I prevent my pet from getting heartworm disease?
Simple! Your pet should be on a monthly (every 30 days) heartworm preventative. They come in pills, topicals solutions, and injections. All veterinarians in the Southeast recommend preventatives year-round as well as annual blood testing.
What about cats?
Yes! While we think of heartworm disease as a dog disease, cats get infected as well. It looks and acts much differently in cats than it does in dogs. It is also much more difficult to test for in cats. Cats are much more sensitive to heartworm as even exposure to heartworm larva can cause significant lung inflammation. The most common symptoms of heartworm disease in cats are chronic vomiting and sudden death (scary!). We recommend that even indoor-only cats be on a regular, monthly, heartworm preventative.