SlimDoggy Health Check : Heartworm Pt.2

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Recently we introduced our new SlimDoggy Health Check series and took a closer look at heartworm and its prevalence throughout the US. Today we want to focus on the causes, symptoms, diagnosis, treatment and prevention of the disease.

Heartworm causes:

We all know that heartworm is a serious disease that causes severe lung & heart problems and potentially other organ failure if not treated quickly. The disease is caused by a parasitic worm called Dirofilaria immitis that is spread through the bite of a mosquito. It is called heartworm because the worms – planted by the mosquito – live in the heart, lungs and other vital organs of the host (mainly dogs, cats & ferrets).
The mosquito is the secondary host and carries the microfilia (worm eggs) from host to host – spreading the disease. (See Lifecycle photo).
Heartworm Lifecycle #4

Heartworm symptoms:

In the early stages of the disease, many dogs show few symptoms or no symptoms at all. The longer the infection persists, the more likely symptoms will develop. Active dogs, dogs heavily infected with heartworms, or those with other health problems often show pronounced clinical signs.
Signs of heartworm disease may include a mild persistent cough, reluctance to exercise, fatigue after moderate activity, decreased appetite, and weight loss. As heartworm disease progresses, pets may develop heart failure and the appearance of a swollen belly due to excess fluid in the abdomen. Dogs with large numbers of heartworms can develop a sudden blockages of blood flow within the heart leading to a life-threatening form of cardiovascular collapse. This is called caval syndrome, and is marked by a sudden onset of labored breathing, pale gums, and dark bloody or coffee-colored urine. Without prompt surgical removal of the heartworm blockage, few dogs survive.
American Heartworm Society


Heartworm diagnosis & treatment:

Given the severity of heartworm, the need for early detection is critical. The diagnosis is made through a simple antigen blood test administered by your vet. If your dogs tests positive, more tests may be required to determine the stage of the disease in order to prepare a treatment plan. If adult heartworms are present your dog may be hospitalized and given medication designed to kill the adult worms.
There are two drugs approved by the U.S. Food and Drug Administration (FDA) for the treatment of heartworm disease in dogs. Both drugs contain arsenic and are effective at killing adult heartworms. Caparsolate Sodium (arsenamide sodium), the older of the two drugs, is injected into a vein. It is not currently manufactured or marketed in the United States. The newer drug, Immiticide (melarsomine hydrochloride), is given by a deep injection into the back muscles to treat dogs with stabilized class 1, 2, and 3 heartworm disease.
US Food & Drug Administration

Heartworm prevention:

Preventing heartworm is as simple as administering a preventive medication each month. It’s important to test your dog for heartworm before starting a regular adminstration of the preventive medication and should always be done under the guidance and the direction of your veterinarian.

Additional Reading:

Keep The Worms Out Of Your Pet’s Heart! The Facts About Heartworm Disease

Heartworm Basics

14 Warning Signs That Your Dog Has Heartworms


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  1. Great post!! I live in Oregon and the heart worm risk is pretty low but I still give the girls a monthly preventative. I’d rather not risk it.
    Lauren Miller recently posted…Shiny!! B&W SundayMy Profile

  2. We are covered. In Germany, they didn’t have heartworm, so no one took the meds which always made Mom a bit nervous, but here we are on the program the first of every month.
    Emma recently posted…My Inner Thief ReturnsMy Profile

  3. The heartworm was no problem here, but during the last two years we had some cases here too. The worst is that we are not prepared for this disease and our common deworming-meds are not helpful. The vets say it’s not essential … but I think better safe than sorry….
    easy rider recently posted…easyblog MOANDAY MONDAYMy Profile

  4. Good article. Heartworm is a serious but preventable ailment.

  5. We have always just taken our medicine, but had never really thought about what the symptoms were! Great post! Thanks for sharing this information!
    MyDogLikes recently posted…Pawz Dog BootsMy Profile

  6. Well done! Heartworm is a nasty disease that is easier to prevent than to treat. Treatment is hard on the dog and then you have to cage rest your dog for a extended period after treatment so when the worms die they aren’t dislodged and cause a serious problem.
    Sand Spring Chesapeakes recently posted…Mischief Monday~Two Mischief’s In One DayMy Profile

  7. Also testing once a year to make sure there hasn’t been a failure in the preventative is important. I know so many people who keep their dogs on the preventative year round and complain that they have to pay for a test. Really the test is the least expensive part. 🙂
    2browndawgs recently posted…Five Reasons to Consider An Electric Fence for Your Hunting DogMy Profile

  8. Heart worm prevention is nothing to play with – great information to share.

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