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Greensboro, NC 27455
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Heartworms In Dogs - Symptoms and Treatments

white shepherds in grassSince 2000 the veterinary staff at North Elm Animal Hospital has made heartworm prevention for dogs an important part of our approach to preventive care. A heartworm infection can lead to numerous health problems up to and including early death. Therefore, heartworm prevention cannot be ignored. Our team is here to educate you and protect your dog from this terrible disease.

Heartworm mapWhile outdoor playtime certainly offers numerous benefits, it also increases the risk of exposure to heartworm in dogs. This does not mean that dogs are completely safe indoors. It simply means that potential exposure to heartworm infection increases with more exposure to the outdoors.

Heartworms are spread to dogs via bites from infected mosquitos. Living in NC, the presence of mosquitoes throughout the spring, summer and early fall months means greater chances for your dog to contract heartworms. Once a heartworm infestation occurs, it will become life threatening. Therefore, our goal is to implement a preventive program before your dog is exposed.

What Is Heartworm Disease?

Heartworm disease in dogs is caused by a blood-borne parasitic nematode (roundworm) known as Dirofilaria immitis which is transmitted by mosquitoes.

Upwards of 30 species of mosquitoes can act as heartworm transmitters. Mosquitoes ingest immature heartworm larvae, called microfilariae, by feeding on an infected dog. The microfilariae develop further for 10 to 30 days in the mosquito's gut and then enter parts of the mosquito's mouth. Heartworms can not be spread directly from dog to dog- they must go through the mosquito. 

When an infected mosquito bites a dog, it injects larvae into the dog. The larvae then mature over a period of several months, eventually ending up in the right side of the heart and the pulmonary arteries. Once this occurs, they mature into adult heartworms in dogs, and can reproduce about six months from the time of invasion. At approximately eight months after the invasion, heartworm in dogs begin to produce a new crop of microfilariae that will live in the dog's blood for about one month. 

Heartworm Symptoms - The Four Stages Of Heartworms In Dogs

Heartworm symptoms in dogs are divided into four stages. It is important to understand that individual stages are not always clearly identifiable and some stages can overlap, but the following information will help educate you about the four major stages, as well as their accompanying symptoms. The four clinical stages of heartworm begin when your dog has already become infected and the heartworms are present in the dog's heart:

Stage 1: In dogs, the first stage of heartworm will typically be symptom free. In this stage the heartworms are present and settling into the heart. However, in stage one the disease has not yet progressed to the point where the heartworms will have produced a new generation of microfilariae and dog's body will not yet have produced antigens in an amount sufficient for detection.

Stage 2: Stage two of heartworms in dogs is accompanied by minimal to moderate symptoms including intolerance for exercise and a more lingering cough. The heartworms have been present long enough in the body for antibody production and probable microfilariae production. During this phase, heartworm disease may be detected with blood tests.

Stage 3: By stage three of heartworms in dogs, the symptoms of the disease will be very noticeable and have a big impact on your dog's health. Dogs continue to cough and experience fatigue after exercise, may be reluctant to exercise at all, and can have trouble breathing. During this stage, dogs may also cough up blood. By stage three, the disease is quite evident on x-rays. The worms cause changes in the heart and large vessels which will be obvious on x rays.

Stage 4: Dogs in stage four of heartworm disease have very visible heartworm disease symptoms. These symptoms are accompanied by long-term implications for the dog's health. These dogs are very ill. The symptoms are similar to Stage 3 but more severe. Dogs will be reluctant to exercise, tired after exercising, and will exhibit a cough. They will probably experience trouble breathing as well. Testing may reveal the impact of the disease in the form of abnormal sounds within the dog's heart and lungs and an enlarged liver. Even with treatment, this stage of the disease carries a high risk of long term debilitation and possible death.

The severity of heartworms in dogs is directly dependent upon:

  • The number of worms present in a dog's body
  • The duration of the incubation
  • The response of the infected dog in fighting off the infestation

As heartworm disease progresses through each stage, the treatment becomes increasingly risky. This is a big reason why early detection plays a major role in the options and ability for your dog to recover. Remain aware of any changes in your dog's behavior. Keep an eye out for any changes in behavior that align with the symptoms of heartworms and if you do find that your dog is displaying symptoms that could be indicative of heartworm disease, it is important to make a veterinary appointment right away.

Other heartworm disease symptoms include:

  • Anemia
  • Fainting Spells
  • Right Sided Chronic Heart Failure
  • High Blood Pressure
  • Rapid Heart Beat

It is important to understand that the symptoms listed above are indicative of advanced stage heartworm disease. Unlike medications that are used to prevent heartworm in dogs, the medications that are used to kill an advanced stage heartworm infection carry a higher rate of potential side effects, can be painful for the dog and are costly to the owner. In addition, the treatment will require considerable downtime for your dog's normal exercise routine while the dog recovers from the infection.

Heartworm Prevention For Dogs

Heartworm prevention is given in the form of a monthly chewable tablet. The chewables are readily accepted by most dogs as a treat. It is very important that the chewable be given once a month to make sure that your dog is adequately protected. The heartworm prevention we recommend at NEAH also prevent intestinal parasites and help with flea control. Side effects of the chewable medication are rare. However, as with any medication, please call if you notice any changes in your dog's health or behavior.

What You Need To Know About Treating Heartworm Disease

The first thing to understand is that there is a significant difference between heartworm prevention and heartworm treatment. Preventatives are simple to give and are effective in protecting your dog against heartworm disease. Treatment medications are used for dogs that are already sick because they have become infected.

The first step in heartworm treatment is obtaining a diagnosis. We use an in house blood test to determine the presence of heartworms in dogs. 

A positive heartworm blood test in the first step in diagnosis. If the blood test comes back positive, then the following tests may also be performed to determine the stage and severity of the disease in order to determine the most appropriate treatment plan:

  • A microfilaria test determines the presence of the baby heartworms that allow the mosquito to transmit the worms to another dog
  • Radiographs, or X-Rays to view the size and shape of a dog's heart. This is helpful because many dogs with heartworm develop enlarged pulmonary arteries, or have obstructions in the arteries leading to the lungs
  • Blood tests to evaluate liver and kidney function

Once diagnosed with heartworm disease, dogs are put on a heartworm prevention for three months to keep any additional heartworm larvoe from maturing in to adult heartworms. Then most patients are hospitalized to receive an adulticide called Immiticide, which is an injection that kills adult heartworms. The patient must be kept quiet for a month while most of the worms are dying and being resorbed by the body. If the dog begins coughing or acting in any way ill after the treatment the veterinarian must be contacted. A month later the dose is repeated at a higher dose to kill all remaining heartworms. The microfilariae in the body can be eliminated with a monthly prevention, which can be administered at home.


Ask Your Veterinarian About Heartworm Medicine For Dogs

It is important to consult your veterinarian when making preventive care decisions for your dog. This is true for a variety of reasons. There are many over the counter products on the market today that range from ineffective to outright dangerous. Our veterinarians are trained and qualified to help you make the best decisions regarding preventive care and treatment of any health conditions your dog may develop, especially when it comes to parasitic infections.

Schedule An Appointment To Diagnose Or Prevent Heartworm In Dogs

Heartworm is an easily preventable disease. If your dog is not currently using a veterinarian recommended heartworm prevention medication, please schedule an appointment right away. There is no reason for your dog to be exposed to heartworm disease, when prevention is so simple.

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