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Heartworms in Dogs

November 15th, 2019
Heartworms in Dogs

Heartworm disease is one of the most serious health issues a dog can have. If untreated, it can be fatal. Fortunately, it’s entirely possible to prevent heartworm disease and there is treatment available if your dog contracts heartworm.

What are Heartworms in Dogs?

Dirofilaria immitis, more commonly known as heartworm disease or heartworms, is a disease caused by nematode or roundworms. It varies in severity based on the number of worms in the body and the length of time they’ve been in the dog. The dog’s immune system can also play a role in the severity of the disease.

In areas where heartworm disease is common, dogs are all but guaranteed to develop the disease without medication. It is mainly found in tropical and subtropical climates but can affect dogs just about anywhere, so it’s important to speak to your vet about preventative measures regardless of where you live. There have been incidents of dogs diagnosed with heartworm in all 50 states in the USA.

  • What Causes Heartworm Disease?
What Causes Heartworm Disease

Dogs contract heartworms from mosquito bites. Mosquitoes carry heartworm larvae that enter the body at the site of the bite and travel to the heart and blood vessels in the lungs. From the time of the bite until the dog begins to show symptoms typically takes about six months. Once in the heart and lungs, the larvae grow into adults and reproduce, then lay eggs that develop into baby heartworms in the bloodstream. An adult heartworm can be as long as 12 inches.

Heartworms are contagious via mosquito bites. If a mosquito bites an infected dog and then bites an uninfected dog, the second dog can become infected.

There are several things that place your dog at a heightened risk of contracting heartworms, including:

  • Living in an area where heartworms are prevalent
  • Living or visiting an area where there are a lot of mosquitoes
  • Not taking heartworm prevention medication

All dogs in the United States should be using heartworm preventative medication. Your dog’s veterinarian can suggest which medication will work best and recommend how often to take it.

  • Symptoms of Heartworms in Dogs

It’s possible for your dog to contract heartworms and not show any symptoms for some time. There are actually stages of heartworm disease and depending on what stage your dog is in the symptoms will vary.

In general, the basic symptoms of heartworms include coughing, exercise or physical activity intolerance, and generally poor health.

  • Stages of Heartworm Disease

The stage of heartworm disease will affect your dog’s symptoms and his or her overall health. The stages are as follows:

  • Stage 1

Stage 1 dogs rarely show any symptoms of a heartworm problem. Occasionally they’ll develop a cough, but otherwise, you might not even know they are sick. It’s possible to give a dog in this stage a blood test, but it could produce a negative result, even though they are infected.

  • Stage 2

Stage 2 dogs typically have a cough and tend to find moderate physical activity challenging. Chances are good a dog in stage 2 will produce a positive result on a heartworm test.

  • Stage 3

In stage 3, dogs tend to be noticeably ill. They develop poor body condition, including loss of muscle and general weight loss, and have greasy or dry, brittle hair. They have a greater intolerance for physical activity and tend to exhibit labored breathing with minimal exercise. They develop fluid retention and might have a potbelly. This is caused by a failure on the right side of their heart. Some dogs cough up blood in this stage and the worm infestation is easily seen on x-rays.

  • Stage 4

Dogs with stage 4 heartworms develop caval syndrome, which occurs when heartworms block blood flow to the heart. It might still be possible to treat a dog that has stage 4 heartworms, but treatment for dogs in this stage is sometimes palliative only to keep them comfortable as the disease progresses and reaches a fatal stage.

The further along the disease has progressed the more invasive the treatment needed to stop it. The best-case scenario is noticing a problem in stage 1 or early in stage 2 before heartworms have affected your dog’s health long-term. If your dog seems reluctant to exercise, has a cough, or seems more lethargic than usual, contact your vet. If the problem continues even if a heartworm test is conducted and come back negative, as that your vet conduct the test again.

The best thing you can do is to give your dog heartworm preventative medication that prevents any larvae infection your dog has contracted from developing into adult heartworms. Annual testing for heartworm is also a good idea even if your dog has no visible symptoms.

  • Diagnosing Heartworms in Dogs
Diagnosing Heartworms in Dogs

The most common way to officially diagnose heartworms in dogs is to conduct a blood test. Blood tests can come back negative, though, especially during the very early stages of the disease.

Heartworm tests are fairly routine and retire taking a sample of blood from your dog and having it evaluated at a lab. The tests are given to dogs suspected of having contracted the disease and those who are taking preventative medications, just in case.

If your dog tests positive for heartworms, chances are your vet will conduct a second test to confirm the results of the first. This also helps to rule out the presence of microfilariae in the dog’s bloodstream. Additionally, dogs suspected of having heartworm might be given:

  • Urinalysis
  • Chest x-rays
  • Blood chemistry panel
  • Complete blood cell count

The results of these tests are used by the vet to help plan an appropriate course of treatment. Staging the disease makes it easier to choose the least invasive treatment that is likely to work. The tests can also help your vet give your dog the appropriate prognosis and help you understand what you can expect concerning your dog’s health.

  • Heartworm Prognosis

The prognosis for dogs who contract heartworm disease tends to be promising, especially when cases are caught early and staged in the mild to moderate range. Heartworm treatments are very effective and have relatively few side effects.

When a case is more severe, there can be a greater risk for long-term complications. Heartworms can be fatal, but even if a dog survives after a late-stage bout with heartworms, it can affect his or her health for a long time to come.

In addition to heartworm medication, sometimes referred to as “deworming,” dogs might undergo additional supplemental treatments. These treatments can include oxygen therapy, anti-inflammatory medications, and surgery. For most dogs, treatment will last several months and it will take nine months before a vet can give the “all clear” for heartworm infestation after conducting an antigen test.

Most dogs are put on exercise restrictions and must be closely monitored for at least nine months after the diagnosis is made.

  • Heartworm Treatment in Dogs

Treatment for heartworm in dogs depends on how far the disease has progressed. Dogs with advanced heartworms will need to undergo treatment to stabilize their overall health first and foremost. For instance, it might be necessary for a dog to receive oxygen therapy if there are issues with blood flow when the infestation is first recognized. Dogs with less advanced stages might be fine in terms of their immediate health, but need to be dewormed with medication.

All dogs diagnosed with heartworm disease are prescribed a medication to kill microfilariae. Usually, several rounds of injections are also required to kill the adult worms in the lungs and heart.

Dogs can react poorly to the death of heartworms, which triggers a variety of side effects to the treatment. Most dogs require hospitalization during these rounds of injections so vets can monitor them for side effects. Your dog might be given additional prescription medications to reduce the risk of side effects.

Additionally, dogs are given anti-nausea and pain medication to combat other symptoms associated with the injections.

Conventional treatment, which is a series of injections that utilizes the drug Immiticide (melarsomine), can be very risky for your dog. Even the manufacturer of the drug warns its product has “a low margin of safety.” And some dogs who underwent treatment did not experience any positive outcome – many still had heartworms after the invasive injections.

Every case is different and your dog might require additional treatment for heartworms. Keep in mind, without treatment heartworm will eventually be fatal. It’s also important to remember the earlier treatment begins the less invasive (and less expensive) it will be.

  • Surgery for Treating Heartworms in Dogs
Surgery for Treating Heartworms in Dog

In advanced cases of heartworms, surgery might be recommended to remove the adult heartworms from the heart. This reduces the risk of complications from a blockage of blood flow by the worms.

Though surgery can be effective for preventing problems related to blood flow, it comes with its own set of risks. This is due, in part, to the fact that dogs with advanced stages of heartworm disease already have compromised heart and lung function.

Many dogs with stage 4 heartworms don’t make it even if they undergo treatment, including surgery. And while surgery is effective, it only removes some of the worms in the dog’s body. Adult worms remain in the pulmonary arteries and there might also be larvae elsewhere in the body, so dogs that undergo surgery are also subjected to injection treatment and all that goes with it.

What’s important to note here is that surgery is not an alternative to other treatments. Rather, it is performed in addition to the other treatments because the problem is so dire.

  • Treating Heartworm in Dogs with Natural Products

There are a number of natural treatments available for treating heartworms. You should never give your dog medication or treatment, regardless of whether it is advertised as natural, without first consulting your veterinarian. Even natural treatments can cause side effects and if your dog is dealing with any other health issues, natural treatment for heartworms could interfere with other concerns.

In some cases, natural treatments are used for older dogs or dogs in more advanced stages of heartworm disease because they are not strong enough to undergo conventional injections. Some of these treatments are designed to strengthen a dog’s life. It might not eliminate heartworms, but it can extend the period of time your dog has to live comfortably and enjoy his or her time.

If you aren’t comfortable with the initial recommendation given to you by your veterinarian, it’s best to consult a second vet for his or her opinion. Making the best choice for your dog’s health, especially when faced with a difficult diagnosis such as heartworms, can be scary and intimidating. The more information you have from reputable sources the better informed you’ll be and the easier it will be to determine the course of treatment that will most benefit your dog. Sometimes that’s a blend of conventional and natural remedies that will keep your dog feeling his or her best, regardless of the long-term prognosis of a health condition.

  • Managing Heartworms in Dogs

In addition to the medical treatments your dog must undergo when diagnosed with heartworm disease, there are also things you’ll need to do to manage your dog’s health.

Exercise restriction is one of the most important factors in helping your dog recover. In some cases, a dog with advanced heartworm disease will need to be crated or penned to prevent too much activity. The strain that physical activity puts on a dog’s heart can be too much when it’s already compromised from heartworm disease. And physical activity can result in worms getting into your dog’s bloodstream, which can be fatal. Physical activity might need to be limited for as much as six to nine months after your dog first receives his or her diagnosis.

A follow-up test is also needed following a round of heartworm treatment. This test is typically administered about six months after a dog completes treatment. It looks for the presence of dirofilaria immitis and if the test comes back positive, another treatment round will be needed.

It’s also important that dogs that have been infected take preventative medications as directed. A bout of heartworm disease does not make a dog immune to a second infection in the future. Furthermore, if any permanent damage was done during the first bout, it can be more difficult for your dog to recover if a second infection occurs.

  • Preventing Heartworms in Dogs
Preventing Heartworms in Dogs

Preventing your dog from developing heartworms in the first place is the absolute best way to “treat” heartworms in dogs. Heartworm disease is entirely preventable with medicine that is prescribed by your veterinarian. The medicines are safe and effective, and rarely produce any serious side effects aside from mild nausea and/or vomiting and even this is extremely rare. Most dogs can tolerate monthly heartworm medications without any problems at all and some even look forward to it. It is given in a chew and some consider it a treat.

If you miss a dose or are late giving a dose of preventative heartworm medication you should have your dog tested for heartworms before administering the dose. Routine heartworm screening is a smart thing to do for a dog, even if you are diligent about giving medication. Preventative measures are not 100 percent effective but tend to have a higher success rate when used properly.

Additionally, there are several all-natural ways you can reduce your dog’s risk of contracting heartworms. These should never be used as a replacement for preventative medication, but in addition to in order to further reduce the risk of a problem.

Since a mosquito bite is required for a dog to first contract heartworms, the more you can do to reduce your dog’s chances of getting bitten by a mosquito the better. There are plenty of great natural sprays available that repel mosquitoes and keep your dog bite-free. Also, avoid areas with overgrown grass or where you know there are a lot of mosquitoes. Mosquitoes can carry other diseases, in addition to heartworm, so the more you do to reduce the risk for bites the happier and healthier your pup will be.

Treating heartworms in dogs is expensive and poses a risk in and of itself to the dog. Your best bet and the best thing you can do for your dog’s health is to use a preventative treatment as directed. In most cases, a lifetime of prevention will be less expensive than treating a dog one time if he or she contracts heartworm disease.

What Should You Know about Heartworms in Dogs?

  • Heartworms in dogs are potentially fatal
  • Heartworm disease is almost entirely preventable
  • Heartworms might not have any detectable symptoms in it the earliest stage of development
  • Heartworm treatment lasts several months
  • Recurring infestations are possible
  •  Treatments come with their own list of side effects and complications