Heartworm Disease and Prevention

Did you know you could buy 7.5 years of heartworm prevention for less than the cost of treating your dog 1 time for heartworms?

What is heartworm disease?

Heartworm disease is a serious and potentially fatal disease that most commonly affects dogs, cats, and ferrets. The disease is caused by foot-long worms, otherwise known as heartworms, that live within the heart, lungs, and associated blood vessels of the affected animals. This can cause severe lung disease, heart failure, and damage to other organs in the body.

Dogs are a natural host for heartworms.

Heartworms that live inside a dog may mature into adult worms, and further mate and produce offspring. Left untreated, numbers increase to several hundred. Due to the destructive nature of heartworms, the disease causes lasting damage to the heart, lungs, and arteries then affects the dog’s health and quality of life long after the parasites are gone. This is why prevention is the best option, followed by treatment as early as possible to dogs that are affected.

Cats are affected by heartworms differently.

Cats are not a natural host for heartworms, thus the worms do not survive to the adult stage. This means the number of worms found in cats is far lower. However, this does not diminish the threat and real damage that can be done to a cat’s health. The disease can cause a condition known as heartworm-associated respiratory disease (H.A.R.D.). Heartworm disease often goes undiagnosed in cats, so it is important to screen your pet routinely for the disease. Medications used to treat heartworm infections in dogs cannot be used in cats, so heartworm prevention is the only means of protecting cats.


How is heartworm disease transmitted?

It all starts with a mosquito with a voracious appetite for blood and an infected animal.
When a mosquito bites and draws blood from an infected animal, it picks up the microscopic baby worms (called microfilaria) that circulate in the blood stream. These baby worms develop and mature into the infected stage of the larvae over a 10 to 14 day period. When a mosquito then bites another susceptible animal, the infective larvae is deposited into the surface of the animal’s skin that enters the new host found in the mosquito’s bite wound. Once inside, it takes approximately 6 months for the larvae to mature into adult heartworms. Once matured, heartworms live for 5 to 7 years in dogs, 2 to 3 years in cats. Due to the longevity of worm life, the number of worms increases in affected pets with each mosquito season.


What are the signs of heartworm disease?

Signs in dogs are almost asymptomatic at first.

The longer the infection, the more symptoms will develop. Take note of a mild persistent cough, reluctance to exercise, fatigue after moderate activity, decreased appetite, and weight loss. As the disease progresses, pets may develop heart failure and the appearance of a swollen belly due to excess fluid in the abdomen. Other risks of a large number of heartworms include sudden blockages of blood flow within the heart leading to life-threatening cardiovascular collapse called caval syndrome. It is noted by a sudden onset of labored breathing, pale gums, and dark bloody or coffee-colored urine. Few dogs survive if surgical removal of heartworm blockage is not prompt.


Signs in cats are all or nothing.

Either you know nothing of the infection, or a cat is coughing, having asthma-like attacks, periodically vomiting, has a lack of appetite, or is losing weight. Not always, but occasionally an affected cat may experience fainting, seizures, trouble walking, or suffer from fluid accumulation in the abdomen. Prevention is strongly recommended, as treatment is not available for cats and first signs often result in sudden death.


How much are my pets at risk for heartworms?


When should my pet be tested for heartworms?

Have your dog tested every 12 months for heartworms, and give a heartworm preventative once a month for 12 months. Typically heartworm tests are done during a routine visit for preventative care.

Puppies under 7 months of age can be started on heartworm prevention without a heartworm test. After 7 months of age and previously not on a preventative need to be tested prior to starting heartworm prevention. They also need to be tested 6 months and 12 months later, and annually after that. Annual testing is necessary even for dogs on heartworm prevention year-round, to ensure that the prevention program is working. Although highly effective, heartworm prevention is not 100 percent effective.

Due to the progressive, and serious nature of the disease, the earlier it is detected, the better chances of recovery or survival. Because symptoms are slow to show, if at all, in infected animals, it is important that a heartworm test is administered by your veterinarian.

For dogs, tests include only a small blood sample, which will be used to detected the presence of heartworm proteins. Some veterinarians test in-house, others send samples to a diagnostic laboratory. In either case, results are obtained quickly. If tested positive, further tests may be ordered.

At River Landings Animal Clinic, we test canine samples in-house for faster results and feline samples to a diagnostics lab due to infrequency and ambiguity.

Cats are less likely to have adult heartworms, so heartworm detection is more difficult. The preferred method of screening cats is using both an antigen and antibody test, or x-rays or ultrasounds to look for heartworm infections. Cats are to be tested prior to being put on prevention and re-tested.


What are the heartworm treatment options for my pet?

There is substantial risk in treating a dog for heartworms, however, if a dog is in good health, serious complications are less likely. The goal of treatment is to kill the adult worms and microfilariae (microscopic worms) in your dog, as safely as possible. Take note that the heartworms are dying inside the dog’s body. Treatment requires complete rest. Additional medications may be necessary to help control the body’s inflammatory reaction as worms die and are broken down in the dog’s lungs.

There is no effective or safe medical treatment for heartworm infection or heartworm disease in cats. Your veterinarian may recommend medications to reduce inflammatory response or high-risk surgery to remove the heartworms.


How can heartworm be prevented?

Heartworm infection is almost 100 percent preventable in dogs and cats. With several FDA-approved heartworm preventatives on the market in a variety of formulations, it is best to get your veterinarian's recommendation best suited for your pet’s lifestyle and risks.

Did you know you could buy 7.5 years of heartworm prevention for less than the cost of treating your dog 1 time for heartworms?

As of September 21st, we have a limited-supply deal offered at River Landings Animal Clinic. When you buy a year’s supply of Trifexis, you receive a mail-in rebate of $50 and two free doses (up to $47). Ask us about our ongoing specials. With a year's supply, you won’t have to make a monthly reminder to protect your pet -- and you save money in the end!

Hear From Us Again

Don't forget to subscribe to our email newsletter for more recipes, articles, and clinic updates delivered to your inbox (here). Or, you can keep up to date by liking and following our Facebook page (here).