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Your pet's wellness is important.  Larn the facts about heartworm illness so you tin keep your pet healthy and heartworm-free.

Dogs

Cats

Ferrets

Heartworm Disease – What Is It and What Causes It?

adult heartworms in a dog's heart

Photo courtesy of Matt W. Miller, DVM, MS, Diplomate ACVIM (Cardiology)

heartworms

Photo courtesy of Matt W. Miller, DVM, MS, Diplomate ACVIM (Cardiology)

Heartworm disease is a serious illness that results in severe lung disease, middle failure, other organ damage, and decease in pets, mainly dogs, cats, and ferrets. Information technology is acquired by a parasitic worm called Dirofilaria immitis.The worms are spread through the bite of a mosquito.  The dog is the definitive host, pregnant that the worms mature into adults, mate, and produce offspring while living within a dog.  The mosquito is the intermediate host, meaning that the worms live inside a mosquito for a short transition flow in lodge to go infective (able to cause heartworm disease).  The worms are called "heartworms" because the adults live in the heart, lungs, and associated blood vessels of an infected fauna.

In the United States, heartworm affliction is most common forth the Atlantic and Gulf coasts from the Gulf of Mexico to New Bailiwick of jersey and along the Mississippi River and its major tributaries, but it has been reported in dogs in all 50 states.

The Heartworm Lifecycle in Dogs

Copper-colored Dog

In an infected dog, woman heartworms release their offspring, called microfilariae, into the dog's bloodstream.  When a musquito bites the infected dog, the mosquito becomes infected with the microfilariae.  Over the next 10 to 14 days and under the right environmental conditions, the microfilariae get infective larvae while living inside the mosquito.  Microfilariae must pass through a mosquito to get infective larvae.  When the infected mosquito bites another dog, the mosquito spreads the infective larvae to the domestic dog through the seize with teeth wound.  In the newly infected canis familiaris, it takes virtually 6 to 7 months for the infective larvae to mature into adult heartworms.  The adult heartworms mate and the females release their offspring into the dog'southward bloodstream, completing the lifecycle.  See a graphic of the heartworm lifecycle in dogs.

Heartworm disease is not contagious, meaning that a domestic dog cannot take hold of the disease from beingness nigh an infected dog.  Heartworm disease is just spread through the seize with teeth of a mosquito.

Within a dog, a heartworm'south lifespan is 5 to 7 years.  Adult heartworms wait similar strands of cooked spaghetti, with males reaching nearly 4 to 6 inches in length and females reaching about 10 to 12 inches in length.  The number of worms living within an infected dog is called the worm burden.  The boilerplate worm burden in dogs is fifteen worms, but that number can range from i to 250 worms.

How is a Dog Tested for Heartworms?

A veterinarian uses blood tests to check a dog for heartworms. An antigen test detects specific heartworm proteins, called antigens, which are released by adult female heartworms into the dog'southward bloodstream.  In nigh cases, antigen tests tin can accurately detect infections with one or more adult female heartworms. The primeval that the heartworm proteins tin can exist detected in a canis familiaris's bloodstream is about 5 months after information technology is bitten by an infected musquito.

Some other test detects microfilariae in a domestic dog's bloodstream.  Microfilariae in the bloodstream indicate that the dog is infected with developed heartworms (because but developed heartworms can mate and produce microfilariae).  The earliest that microfilariae can be detected in a dog's bloodstream is about 6 months after it is bitten past an infected mosquito (because it takes nearly that long for the heartworms to develop from infective larvae into adults that mate and produce microfilariae).

When Should a Domestic dog Be Tested for Heartworms?

The timing and frequency of heartworm tests depend on many factors.  Some of these factors include:

  • The dog'southward age when heartworm prevention is started;
  • If the owner forgot to give heartworm prevention and for how long;
  • If the dog is switched from one type of heartworm prevention to some other;
  • If the canis familiaris recently traveled to an area where heartworm disease is more common; and
  • The length of the heartworm season in the region where the dog lives.

Dogs that are 7 months of age and older should be tested for heartworms before starting heartworm prevention.  A domestic dog may appear healthy on the outside, merely on the inside, heartworms may be living and thriving.  If a heartworm-positive dog is not tested before starting a preventive, the dog volition remain infected with adult heartworms until it gets sick plenty to prove symptoms. Heartworm preventives practise non kill adult heartworms. Also, giving a heartworm preventive to a canis familiaris infected with adult heartworms may be harmful or deadly.  If microfilariae are in the domestic dog's bloodstream, the preventive may cause the microfilariae to of a sudden die, triggering a shock-like reaction and mayhap death.

Annual testing of all dogs on heartworm prevention is recommended.  Talk to your dog'southward veterinary about the best time for your canis familiaris's almanac heartworm test.

What are the Symptoms of Heartworm Disease in a Dog?

The severity of heartworm disease is related to how many worms are living inside the dog (the worm burden), how long the dog has been infected, and how the domestic dog's body is responding to the presence of the heartworms.  The domestic dog's activeness level besides plays a role in the severity of the illness and in when symptoms are start seen.  Symptoms of heartworm illness may not be obvious in dogs that have depression worm burdens, have been recently infected, or are not very active.  Dogs that have heavy worm burdens, have been infected for a long fourth dimension, or are very active often show obvious symptoms of heartworm disease.

In that location are iv classes, or stages, of heartworm illness.  The college the grade, the worse the disease and the more obvious the symptoms.

  • Course 1:  No symptoms or balmy symptoms such equally an occasional cough.
  • Form 2:  Balmy to moderate symptoms such every bit an occasional coughing and tiredness after moderate activity.
  • Form 3:  More severe symptoms such equally a sickly advent, a persistent cough, and tiredness after mild activity.  Trouble breathing and signs of heart failure are common. For form two and 3 heartworm disease, heart and lung changes are commonly seen on chest 10-rays.
  • Class 4:  Also called caval syndrome.  There is such a heavy worm burden that blood flowing back to the heart is physically blocked by a large mass of worms.  Caval syndrome is life-threatening and quick surgical removal of the heartworms is the only treatment selection.  The surgery is risky, and even with surgery, most dogs with caval syndrome dice.

Not all dogs with heartworm disease develop caval syndrome.  Nonetheless, if left untreated, heartworm disease will progress and harm the dog's heart, lungs, liver, and kidneys, eventually causing decease.

Is There a Handling for Heartworm Disease in Dogs?

Melarsomine dihydrochloride (available under the trade names Immiticide and Diroban) is an arsenic-containing drug that is FDA-approved to impale developed heartworms in dogs. It's given by deep injection into the back muscles to treat dogs with stabilized class i, 2, and 3 heartworm disease. Another drug, Advantage Multi for Dogs (imidacloprid and moxidectin), is FDA-approved to go rid of microfilariae in the dog's bloodstream. Advantage Multi for Dogs is a topical solution applied to the canis familiaris's skin.

The treatment for heartworm disease is non like shooting fish in a barrel on the dog or on the owner's pocket book.  Treatment can be potentially toxic to the dog's body and tin can cause serious complications, such every bit life-threatening blood clots to the dog's lungs.  Treatment is expensive because it requires multiple visits to the veterinarian, blood tests, ten-rays, hospitalization, and a series of injections.

The All-time Treatment is Prevention!

Many products are FDA-approved to preclude heartworms in dogs.  All require a veterinarian'due south prescription.  Most products are given monthly, either equally a topical liquid practical on the skin or as an oral tablet.  Both chewable and non-chewable oral tablets are available.  One product is injected nether the pare every vi or 12 months, and only a veterinarian tin can give the injection.  Some heartworm preventives incorporate other ingredients that are effective confronting certain intestinal worms (such as roundworms and hookworms) and other parasites (such every bit fleas, ticks, and ear mites).

Year-round prevention is best!  Talk to your dog'southward veterinary to make up one's mind which preventive is best for your dog.

The American Heartworm Club advocates to "Recollect 12." Requite dogs 12 months of heartworm prevention and go them tested for heartworms every 12 months.

orange colored cat

Can Cats Get Heartworm Disease?

Cats tin also become heartworms after being bitten by an infected musquito, although they are not as susceptible to infection as dogs.  A cat is not a natural host of heartworms because the worms do non thrive every bit well inside a cat's trunk.  Both indoor and outdoor cats are at hazard for heartworm disease.

Is Heartworm Affliction Unlike in Cats?

Heartworm disease in cats is a fleck unlike than in dogs.  Heartworms in cats do not live every bit long (boilerplate lifespan is but 2 to 4 years) or grow equally long, and fewer of them mature into adults.  Worm burdens are lower in cats than dogs. Usually a cat has only 1 or 2 worms. However, due to its relatively small body size, a cat with simply a few worms is all the same considered to be heavily infected.

In cats, it takes 7 to 8 months for infective larvae to mature into adult heartworms and produce microfilariae.  This is about one calendar month longer than in dogs.  The presence of microfilariae in a cat'southward bloodstream is uncommon.  Only xx percent of cats with heartworm illness have microfilariae in the bloodstream, compared to 80 to ninety pct of dogs with heartworm disease.  Also, the presence of microfilariae in the bloodstream is inconsistent and short-lived in cats.

It is harder to discover heartworm infections in cats than in dogs.  Veterinarians more often than not use 2 types of blood tests in combination to check a cat for heartworms.  However, negative test results do not rule out heartworm infection, and positive test results may or may not mean that in that location is an agile heartworm infection.  A veterinarian uses the results of both claret tests, along with the cat'southward symptoms and the results of other tests such equally x-rays and an ultrasound of the centre, to make up one's mind if a true cat has heartworm disease.

What are the Symptoms of Heartworm Disease in Cats?

Non all cats with heartworm disease show symptoms. Some cats are able to spontaneously rid themselves of heartworms without having any symptoms. However, some infected cats die suddenly from heartworm illness without e'er showing signs of being ill. Cats with heartworm affliction may accept very nonspecific symptoms that mimic many other cat diseases. These nonspecific symptoms include airsickness, decreased activeness and appetite, and weight loss. Cats with heartworm affliction rarely prove signs of heart failure.

In cats that testify symptoms of heartworm disease, respiratory signs are the most obvious due to the lung harm caused by the heartworms.  Cats typically show symptoms of heartworm disease at ii time points – when the immature heartworms go far in the arteries of the heart and lungs and when the adult heartworms dice.

The young heartworms go far in the heart and lung arteries about 3 to four months afterwards a cat is bitten by an infected mosquito.  Many of these young heartworms die, causing a strong inflammatory response in the true cat's lungs.  This response is called heartworm associated respiratory disease (HARD) because respiratory signs, such as trouble breathing, increased respiratory rate, and cough, are the most obvious. Information technology may exist difficult to distinguish Difficult from feline asthma or feline bronchitis.

When the adult heartworms die, they release toxins into the cat'due south bloodstream which crusade lung impairment, leading to respiratory problems or sudden decease.  Fifty-fifty the death of 1 worm tin be fatal for a true cat.

In that location is no FDA-canonical drug to treat heartworm disease in cats, although symptoms may be managed with medications.  Surgical removal of adult heartworms may be a treatment option if the heartworms tin be seen by ultrasound.  Just surgery is risky, and if the heartworms are non removed intact, at that place can be potentially serious complications, such as daze and expiry.

Again, Prevention is the Best Handling!

Several products are FDA-approved to forestall heartworms in cats.  There are both topical and oral products for cats, and all are given monthly and require a veterinarian's prescription.  Some heartworm preventives contain other ingredients that are effective against certain intestinal worms (such as roundworms and hookworms) and other parasites (such equally fleas, ticks, and ear mites).

Again, year-round prevention is best!  Talk to your cat's veterinarian to decide which preventive is best for your true cat.

Should Cats Be Tested for Heartworms?

It is recommended that cats be tested for heartworms before starting heartworm prevention, although this pre-testing is less useful than in dogs. Talk to your true cat'due south veterinarian about testing your cat for heartworms.

ferret

Photo courtesy of David A. Crum, DVM, MPH

What about Heartworm Disease in Ferrets?

Ferrets can too get heartworms from the bite of an infected mosquito.  Ferrets are like to dogs in their susceptibility to heartworm infections, but their symptoms are more similar to those seen in cats.

Infected ferrets typically have low worm burdens, and microfilariae are seen in the bloodstream in only 50 to lx percentage of ferrets with heartworm affliction.  Symptoms of heartworm disease in ferrets include decreased activity level, coughing, trouble breathing, and overall weakness.  Heart failure can occur in astringent cases.  Based on a ferret's symptoms, a veterinarian may perform chest x-rays and an ultrasound of the heart to determine if it has heartworm affliction.  Blood tests to discover heartworm infections in ferrets are by and large unreliable.

No drugs are FDA-approved to care for heartworm affliction in ferrets. And only one drug, Advantage Multi for Cats (imidacloprid and moxidectin), is approved to prevent heartworms in ferrets. Available only with a veterinarian'due south prescription, it is a topical solution that is practical monthly. As well preventing heartworms, Reward Multi for Cats also treats flea infestations on ferrets by killing adult fleas.

Again, prevention is the all-time handling!  Year-round prevention is recommended for all ferrets.  Talk to your ferret's veterinarian near preventing heartworm disease in your furry friend.

Can People Become Heartworms from Their Pets?

People cannot get heartworms from their pets.  Heartworms are just transmitted by the seize with teeth of an infected musquito.  In rare cases, people tin get heartworms after being bitten past an infected mosquito.  But because people are non a natural host for heartworms, the larvae normally drift to the arteries of the middle and lungs and die before they become adult worms.

How Can I Get More Information on Heartworm Disease?

  • Talk to your pet's veterinarian
  • Contact the FDA's Center for Veterinarian Medicine at 240-402-7002 or AskCVM@fda.hhs.gov
  • Read Forbid Heartworms in Dogs, Cats, and Ferrets Year-Round
  • Visit the American Heartworm Society'south website at www.heartwormsociety.org/
  • Visit https://world wide web.petsandparasites.org/

*Special thanks to David A. Crum, DVM, MPH for sharing his ferret expertise.