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What Happens If Dog Heartworm Disease is Left Untreated?

Dog Heartworm Disease Left Untreated

Understanding Heartworm DiseaseWhen Money is an Issue 

If you suspect your dog has heartworms or perhaps your dog was diagnosed with heartworms by your vet, you may be wondering what happens if dog heartworm disease is left untreated. It could be you cannot financially afford heartworm treatment, or perhaps you are concerned about treatment, which may entail medications and keeping your dog at rest. However, dog heartworm disease is one of those conditions that cannot resolve on its own, and left untreated, it can lead to serious complications and even death.

dog mosquito

To better understand what happens when dog heartworm disease goes untreated, it's important to first understand what happens when dogs contract heartworm disease. Dogs are natural hosts for heartworm disease, meaning that heartworm parasites use dogs to complete their life cycle, growing, mating and reproducing inside the dog.

It all starts with a small bite from an infected mosquito. When the mosquito bites, several young heartworm larvae (microfiliaria) end up on the dog's skin and then enter the dog's bloodstream through the bite wound.

Once inside the dog, the young larvae stay within the tissues and then, after several weeks, they start traveling towards the dog's heart where in about 6 to 7 months they will mature into adult heartworms.

Adult heartworms, for sake of an example, resemble long strands of cooked spaghetti measuring anywhere between 4 and 12 inches in length depending on gender. Females tend to be the longest. Heartworms are known for having a lifespan of 5 to 7 years, but they may die earlier than that.

Dogs may have on average about 15 worms, but in severe cases, it's not unheard of some dogs having as many as 250! Once in the dog's body, heartworms wreck havoc in the dog's circulatory system, leading to serious complications and even death.

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Damage to Arteries

Normal pulmonary arteries (the arteries leading from the heart to the lungs) have a smooth surface and blood flows through them with no problems. However, when heartworms establish in the dog's pulmonary arteries, each heart beat causes the worms to be moved back and forth causing irritation and trauma to the arteries' lining.

As time goes by, the presence of heartworms (and their excrement) cause the lining of the arteries to become inflamed, causing deterioration and therefore, significant changes to their appearance. The trauma along with the inflammation (endarteritis) causes the arteries to become thickened and scarred.

Blockage to Blood Flow 

As the heartworms keep growing and wrecking damage to the pulmonary arteries, the passage of blood starts becoming restricted which leads to turbulent blood flow. With high numbers of worms the smaller arteries risk becoming blocked, potentially leading to decreased blood flow and obstruction. Soon, the affected dog's pulmonary blood pressure goes up.

Onset of Heart Failure

As the obstructive disease progresses and starts involving more arteries, the heart's ability to pump blood is compromised. The heart starts therefore pumping against increased pressure due to the heartworms blocking proper blood flow, which ultimately leads to right-sided heart failure as the muscles of the heart grow weaker and weaker.

When dogs develop congestive heart failure, they have a persistent cough, poor exercise tolerance and trouble breathing. As the disease progresses, dogs may develop a swollen belly (ascites) due to the accumulation of fluid in the abdomen.

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Liver and Kidney Damage 

As blood flow deteriorates, the dog's kidneys and liver may also sustain damage. This is because the kidneys and liver are both organs that require high blood flow in order to stay healthy and perform their duties.

Caval Syndrome 

When the numbers of heartworms are very high, they can end up occupying the space in the the right heart and vena cava, a vessel that's responsible for delivering venous blood from the body to the right atrium of the heart.

When the vena cava is blocked, the consequences can be life threatening. Red blood cells get destroyed as the blood makes its ways through the heartworms and their destruction leads to yellowing of the dog's skin and mucous membranes, and presence of blood in the urine. In severe cases, the dog may collapse or even succumb to sudden death.

This is of course, a life threatening situation and affected dogs require immediate surgical intervention so to remove the heartworms. The surgery is not without any risks, and even with surgery, a high amount of dogs will still die.

Normally dogs with heartworm disease are treated with medication and rest, but when dogs have caval syndrome, with so many worms inside the heart, the heart is unable to function normally and surgery must be performed prior to traditional therapy.

The surgery can turn out being quite costly from the anesthesia, the surgery, which is normally performed by a veterinary cardiologist, and the fact of being in the intensive care unit. Costs for dog caval syndrome surgery may easily cost anywhere between $2500 to $5000.

Dog ACTH test costs

Dog ACTH test costs

As seen, heartworm disease is a very serious ordeal and can lead to complications and even death. Prevention, giving monthly heartworm pills is truly worth a pound of cure when it comes to heartworm disease in dogs.

Traditionally, the gold standard to treat dogs with heartworm is giving a series of shots of immiticide which will kill the adult heartworms. The treatment can be quite costly though, and many dog owners cannot afford it, so what's left to do for dog owners who are in a difficult financial situation? Fortunately, there are a few options.

Care Credit is a company that provides healthcare financing for dog owners in difficulty. Dog owners can apply for help and it entails a low interest credit card that can be used towards veterinary bills. Contacting the local vet or local humane society can provide information about any low cost animal hospitals in the area. Some of these hospitals may offer significant discounts, or they may work out a payment plan.

As a last resort, dog owners may ask the vet about the probability of giving the dog ivermectin -based heartworm preventative. Its purpose is to kill any baby heartworms preventing them from being able to mature into adults that may worsen the damage to the dog's heart and lungs.

"In cases in which my clients can't afford heartworm treatment or my patient can't tolerate the treatment, we'll institute ivermectin to prevent new heartworm infection and allow the adult heartworms present to die of old age - which usually occurs within 2 years - but not without causing damage to the cardiovascular and respiratory systems. " ~Dr. Michael Salkin, veterinarian

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  •  DVM360: Pictorial evidence: Heartworm disease and its damage
  • US Food and Drug Administration: Keep the Worms Out of Your Pet’s Heart! The Facts about Heartworm Disease
  • American Heartworm Society: Heartworm Basics

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