Signs of Dog Heartworm Disease in Webster, TX

Heartworm disease can seem very scary for any dog owner. However, with early detection and the proper treatment, most infected dogs can successfully be restored to health.


But make no mistake, left untreated, the disease is serious and potentially fatal. It is caused by foot-long worms, called “Dirofilaria immitis,” that live in a dog’s heart, lungs, and associated blood vessels. The worms are transferred through the bite of a mosquito, and they can cause severe lung disease, heart failure, and damage to other organs.

A dog is a natural host for these parasites, which means that they can mature into adults (after 6 to 7 months after infection), mate, and produce offspring (called “microfilariae”) inside of a dog’s body. Mature male heartworms can reach about 4 to 6 inches, and females can reach 10 to 12 inches. The worms inside of a dog are called “the worm burden,” and the average burden is 15 worms, but it can range anywhere from 1 to 250 worms.

However, even after the worms are gone, the dog’s quality of life and overall health can suffer. So, again, prevention and early treatment (when needed) are the best way to combat the disease’s effects. 

Heartworm has been reported in all 50 states, but it’s most common along the Atlantic and Gulf coasts from the Gulf of Mexico to New Jersey and along the Mississippi river.

Find out more about the signs of dog heartworm disease by continuing to read our Webster, TX, animal hospital’s article.

Dog Heartworm Signs and Symptoms

There are four classes, or stages, of heartworm disease that come with worsening and more severe symptoms as time goes on.

Class 1

When a dog is first infected, they sometimes won’t show any or only mild symptoms (such as an occasional cough).

Class 2

As the disease progresses, mild to moderate symptoms, like tiredness after moderate activity, may become apparent.

Class 3

This is when more severe symptoms, such as a sickly appearance, a persistent cough, tiredness after mild activity, trouble breathing, and signs of heart failure (including coughing when at rest, excessive panting, persistent loss of appetite, swollen belly, and pale or blue gums).

Class 4

This stage is also called “caval syndrome.” It is a sudden form of cardiovascular collapse caused by heartworms that block the blood flow within the heart. Symptoms include the sudden onset of labored breathing, pale gums, and dark or bloody/coffee-colored urine.

Surgical intervention is the only treatment option, but it’s risky, and even after surgery, most dogs with caval syndrome don’t make it.

It should be noted that not all dogs with heartworms develop caval syndrome.

Dog Heartworm Prevention and Testing

When it comes to testing, the American Heartworm Society recommends that you “think 12.”

  1. Get your pet tested every 12 months for heartworm and
  2. Give your pet heartworm preventative all 12 months out of the year

However, the “think 12” method does not apply to puppies under seven months old or dogs over that age that have not been on preventative care.

Puppies under seven months of age can start prevention without a test (as it takes at least six months for a dog to test positive after infection).

But dogs over seven months without prior preventative care need to test before starting prevention because the medication can be harmful for dogs already infected with adult worms. If the offspring is already in the dog’s bloodstream, the preventative may cause the worms to die suddenly. This can trigger a shock-like reaction in the dog (and possibly death).

Our Webster, TX, veterinarian recommends testing at least annually, but every 6 months is preferred, because it can find infection earlier.

Types of Prevention

There are many products, such as oral tablets (chewable and non-chewable) and topical liquids, that the FDA has approved to prevent heartworms, but they all require a prescription from a veterinarian. There are also injections that your vet can administer to your dog. But, of course, even when proper prevention is taken, regular testing is still required as it is not 100% effective. Plus, especially if you go the topical cream or tablet route, your dog may spit out the pill or rub off the cream without you noticing.


A veterinarian uses blood tests to detect heartworms in dogs. The tests detect antigens (known as heartworm proteins), which are released by adult female heartworms into a dog’s bloodstream. Similar testing can be done to detect microfilariae in the bloodstream.


If your dog tests positive for heartworm disease, your vet will likely recommend prescription medications to treat it. They may include:

Melarsomine Dihydrochloride

Also known as Immiticide and Diroban, this is an arsenic-containing drug that kills heartworms. It is administered through deep injections into the back muscles of dogs with stabilized class 1, 2, and 3 heartworm disease. Your vet will determine the injection schedule based on your dog’s condition, but most animals will receive a shot followed by a 30-day period of rest and then two more (24 hours apart) after that.

Advantage Multi for Dogs

Also known as imidacloprid and moxidectin, this is a topical solution that gets rid of microfilariae in the dog’s bloodstream


Many dogs are also given doxycycline to combat potential bacteria (like Wolbachia, which is one of the most common parasitic microbes) that inhabit the heartworm.

Blood Thinners

This is to aid in circulation. 


This is to help the liver tolerate drugs and dying worms. 

In the days (and weeks) after treatment is administered, it’s important that your dog gets as much rest as possible because the worms will die and start to decompose. And as they break up, they are carried to the lungs, where the body reabsorbs them.

But complications can arise if the bits lodge into other parts of the body’s blood vessels, which can be caused by strenuous activity. It’s recommended that you limit your dog to leash exercise outside just long enough to urinate and have bowel movements.

Reach Out to Our Webster, TX, Animal Hospital for Dog Heartworm Prevention

Monthly prevention is of utmost importance, but it isn’t always effective (a dog can be sneaky and rub off creams or spit out pills without you noticing). So, all canines should be tested regularly by their vets to detect infection (and begin a treatment regime) as early as possible.

Schedule your dog’s heartworm testing by giving our Webster, TX, animal hospital a call at (281) 486-1509

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