How do Dogs get Heartworms?

Heartworm disease is a serious and potentially fatal disease in which larval stages of heartworms circulate through a dog’s bloodstream to ultimately establish residence as adults in the dog’s heart and lungs. Left untreated, heartworm disease can result in heart failure, respiratory failure and death. Treatment for heartworm disease is costly, and it is not without risk. Fortunately, heartworms in dogs are easily preventable.

Heartworms in Dogs

Heartworms in Dogs

The vector that is responsible for how do dogs get heartworms is the mosquito. Heartworm disease affects domestic dogs and cats, coyotes, wolves, foxes and sea lions. The answer to how do dogs get heartworms is that a mosquito must first bite an infected animal. When the mosquito, which is now the intermediate host, bites its next victim, the disease is then passed on to that animal. Once this infected mosquito bites a dog, the heartworm larvae that are transmitted through the bite wound develop through several stages until they reach the full maturity of adult worms. This cycle take six to seven months, and the adult worms can live for five to seven years inside the dog’s heart.

Heartworm Symptoms in Dogs

There are often no heartworm symptoms in dogs during the early stage that precedes a buildup of adult worms. As the disease progresses, coughing and exercise intolerance are the first noticeable heartworm symptoms in dogs. In severe cases, the following additional signs and symptoms may be noted:

  • Fainting
  • Lethargy
  • Chronic heart failure
  • Labored breathing
  • Rapid heart rate
  • High blood pressure
  • Enlargement of the right side of the heart

As the adult heartworms accumulate in the heart and pulmonary artery, this results in reduced blood flow to other major organs, including the liver, lungs and kidneys.

Diagnosis of Heartworms in Dogs

The American Animal Hospital Association guidelines recommend annual heartworm screenings on all dogs over the age of six months. This is routinely performed as a simple blood test to detect the heartworm antigen that is released by adult female heartworms. If a dog presents with symptoms of heartworm disease, additional tests may be performed to confirm a diagnosis of heartworm disease. These tests include chest radiographs to observe changes in the right side of the heart and in the pulmonary artery, an electrocardiogram to detect abnormal heart rhythms and an echocardiogram to evaluate the heart’s structure. Heartworms can be seen during an echocardiogram. The combination of these tests determines the extent of the disease and the dog’s overall health status, which is essential in determining the safest and most effective treatment program.

Treatment for Heartworms in Dogs

The goal of treatment for heartworm disease is to eradicate the dog’s body of adult heartworms through a series of adulticide injections. Based on the extent of the dog’s infection, a veterinarian will devise a schedule of injections that will be most effective. When a dog is presented for a round of treatment for heartworm disease, he is kept in the hospital for a few hours following the injection so that the staff can monitor for reactions and side effects. Once an injection is given, adult worms start to die off and break up within a week. When this happens, the decomposing portions are carried through the bloodstream into the dog’s lungs, where they eventually reabsorb into the body. During this stage, strict rest is crucial in order for the dog to make a complete and uneventful recovery. Heartworm preventatives will also be initiated to kill the circulating microfilaria within the dog’s bloodstream. Dogs with severe cases of heartworm disease may require additional treatment drugs, including antibiotics, heart medications to improve compromised cardiac function and diuretics to remove accumulated fluid from the lungs.

Prevention is Imperative

Although the drug used in today’s heartworm treatment protocol is significantly safer than the high levels of arsenic that were administered years ago, it is not without risk. It is a lot easier on you and your canine companion to prevent heartworms in your dog altogether. Most canine heartworm preventatives are available as monthly tablets. Some of them are chewable, and dogs accept them as happily as they do their treats. Depending on the climate of your residential area, your veterinarian may recommend that you give your dog a heartworm preventative throughout the year. Now that you know how dogs get heartworms, find out more about heartworm in cats.

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