VCA Herndon-Reston Animal Hospital

Are You Ready For Summer? Heartworm Preventative

By Tarias Walker
Published: March 15, 2012

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Spring is here and it's just a few short months until summer time is upon us once again. Are you ready for warmer weather? Fun in the sun? Play time outdoors?

If you answered yes, there is one important step that you may be forgetting: Heartworm Prevention.

You may be wondering, "What are Heartworms and how can my pet get them?"

Heartworm disease is a serious and potentially fatal disease. It is caused by a blood-borne parasite that is transmitted by mosquitoes. Adult heartworms are found in the heart and adjacent large blood vessels of infected pets. One dog may have as many as 300 worms present when diagnosed. The life cycle of the heartworm is complicated; the parasite requires the mosquito as an intermediate host before it can complete its life cycle in a pet. As many as 30 species of mosquitoes can transmit heartworms.

The life cycle begins when a female mosquito bites an infected dog or cat and ingests the microfilariae (heartworm larvae) during a blood meal. Once the mosquito bites another dog or cat, the infective larvae enter the body and moves into the bloodstream, then moves to the heart and adjacent blood vessels, maturing to adults, mating and reproducing microfilariae within 6 - 7 months. Cats are generally more resistant to heartworm infestations, and as such are harder to diagnose than dogs.

So, you may be asking, "How can I tell if my pet has Heartworms?"

The signs of heartworm disease depend on the number of adult worms present, the location of the worms, the length of time the worms have been in the pet and the degree of damage that has been sustained by the heart, lungs, liver and kidneys.

Adult heartworms cause disease by clogging the heart and major blood vessels leading from the heart. They also interfere with the valve action in the heart. By clogging the main blood vessel, the blood supply to other organs of the body is reduced, particularly blood flow to the lungs, liver and kidneys, causing these organs to malfunction.

The most obvious clinical signs of heartworm disease are a soft, dry cough, shortness of breath, weakness, nervousness, listlessness and loss of stamina. All of these signs are most noticeable following exercise, when some dogs may even faint or become disoriented. Your veterinarian may notice abnormal lung and heart sounds when listening to the chest with a stethoscope. There may also be evidence of weight loss, poor condition and anemia. Severely infected dogs and cats may die suddenly during exercise or excitement.

We test for heartworms by one of several simple blood tests, and ECG, or X-Rays. Further diagnostic tests are essential to determine if the pet can safely undergo heartworm disease treatment.

"How is Heartworm disease treated?"

There is some risk involved in treating dogs with heartworms, although fatalities are rare. An injectable drug is available that does not have many side effects, allowing successful treatment of more than 95% of dogs with heartworms. These injections may be divided and given thirty days apart, and your dog will have to return 30 days after the adult heartworm treatment to receive a treatment to kill the newly born heartworm larvae.

Complete rest is essential after treatment. The adult worms die in a few days and start to decompose. As they break up, they are carried to the lungs, where they lodge in the small blood vessels and are eventually reabsorbed by the body. This resorption can take several weeks to months and most post-treatment complications are caused by these fragments of dead heartworms. This can be a dangerous period so it is absolutely essential that the dog be kept as quiet as possible and is not allowed to exercise for one month following treatment.

Unfortunately, there is no drug approved for treating heartworms in cats. One of the drugs for treating dogs has been used in cats, but it causes significant side effects. When cats are in a crisis, they are treated with oxygen and corticosteroids ("cortisone") to relieve the reaction occurring in the pulmonary arteries and lungs, and, if needed, drugs to remove fluid from the lungs (diuretics). When they are stable, they are treated continuously or periodically with corticosteroids.

"Wow, that sounds scary! How can I prevent this from happening to my pet??"

You can prevent your pet from getting heartworms by using a heartworm preventive. Veterinarians now strongly recommend that all pets receive year-round monthly heartworm preventative in areas where mosquitoes are active all year round, even cats who live indoors only. With the safe and affordable heartworm preventives available today, such as Revolution, Interceptor, Sentinel, and Vethical products, no pet should ever have to endure this dreaded disease.

So, remember! An ounce of prevention is worth a pound of cure. Ask your veterinarian about Heartworm Preventative today and keep your loving companion safe all year!


Specialty Care

Sometimes sick or injured pets need the care of a veterinary medical specialist. When that happens, VCA specialty hospitals work closely with the general practitioner veterinarians who refer cases to us in order to provide seamless veterinary care to your pet. When your pet is facing any kind of serious illness or injury, our specialty referral hospitals will provide the compassionate and expert care your beloved pet needs.

Our goal is to make sure that when you and your pet are in need that you have access to board certified specialists who are up to date on the very latest developments in their field. In our state of the art hospitals, our specialists also have access to the most sophisticated diagnostic and treatment tools and techniques from ultrasonography and endoscopy to CAT scans and even MRI.

As part of the VCA family, we have over 83 specialty hospitals across the US and Canada which provide referral specialty care, so there may be one near you. Our specialized services include: behavior, cardiology, critical care, dentistry, dermatology, integrative medicine, internal medicine, neurology, oncology, ophthalmology, radiology, rehabilitation, reproduction, and surgery.

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Emergency Care

In case of emergency during normal business hours, please call us immediately. If you have an emergency outside of our normal business hours, please contact a local emergency animal hospital.