Heartworm Prevention

Heartworm is a serious illness that can cause heart failure, lung disease, organ damage, and even death in dogs, cats, and ferrets.


Heartworm Control

Heartworm is a serious illness that can cause heart failure, lung disease, organ damage, and even death in dogs, cats, and ferrets. Heartworm is most prevalent in pets living along the Atlantic Gulf coasts from New Jersey to the Gulf of Mexico and in those living alongside the Mississippi River and its main tributaries. However, it has been found in pets in all of the United States.

Heartworm preventatives we offer:
Dogs: Milbegurd (Oral), Sentinel (Oral), Sentinel Spectrum (Oral)
Cats: Revolution Plus (Topical), Milbegaurd (Oral)

FAQs About Heartworms

What causes heartworm disease?

Heartworm disease is a serious and potentially fatal disease. It is caused by a blood-borne parasite known as Dirofilaria immitis. Adult heartworms are found in the heart, pulmonary artery, and adjacent large blood vessels of infected dogs and cats. Rarely, worms may be found in other parts of the circulatory system. Female worms are 6-14″ long (15 -36 cm) and 1/8″ wide (3 mm). Males are about half the size of females. One dog may have as many as 300 worms present when diagnosed.

Adult heartworms may live up to five years. During this time, females produce millions of offspring called microfilaria. These microfilariae live mainly in the small vessels of the bloodstream.

How is heartworm disease spread?
Since transmission requires the mosquito as an intermediate host, the disease is not spread directly from pet to pet. The spread of the disease, therefore, coincides with mosquito season, which can last year-round in many parts of the United States. The number of dogs infected and the length of the mosquito season are directly correlated with the incidence of heartworm disease in any given area.
How can I prevent my pet from getting heartworms?

You can prevent your dog or cat from getting heartworms by using a heartworm preventative. With the safe and affordable heartworm preventatives available today, no pet should ever have to endure this dreaded disease. Consult with your veterinarian to determine which heartworm preventative program is best for your dog or cat.

Heartworm in dogs

The lifespan of heartworms within an infected dog is between five and seven years and the average worm burden is 15. However, dogs have been seen with worm burdens ranging from one to 250.

Symptoms of heartworm in dogs

The severity of the symptoms of heartworm in dogs is dependent on the worm burden of the animal, how long they have been infected, and how well their body can cope with the disease. However, it is usually broken down into four stages.

Class 1: No visible symptoms or very mild symptoms such as an intermittent cough or wheeze.

Class 2: Mild to more moderate symptoms including intermittent coughing and lethargy or breathlessness after light to moderate exercise. At this time, some heart and lung changes may be seen on X-rays.

Class 3: Symptoms will include frequent or persistent coughing, lethargy, and breathlessness after mild activity. Heart and lung changes will definitely be visible on X-rays.

Class 4: This stage is otherwise known as Caval Syndrome and is reached when an infected animal has been left untreated for an extended period of time. At this stage, the animal experiences restricted blood flow to the heart caused by a blockage of worms. Heart failure is imminent and emergency surgery to remove the worms is the only course of action. However, this comes with its own risks, and most dogs with Caval Syndrome do not survive.

Heartworm in cats

Cats are naturally more resistant to heartworm, and once infected, the worms have a lifespan of only two to three years. Adult worms do not grow as long as seen in dogs, and fewer microfilariae mature into adults. Similarly, there are many fewer microfilariae present in a feline blood stream – an average of only 20% compared to 80 to 90% seen in canines. Worm burdens are also much lower, with an average of only one to three worms seen per cat.

Symptoms of heartworm in cats

Many cats are able to rid themselves of heartworm before any symptoms become evident. However, some infected cats have been known to die without presenting any warning or symptoms.

Once a cat is bitten, they will develop HARD – Heartworm Associated Respiratory Disease. During this time, your cat will experience shallow, rapid, or difficult breathing along with coughing and wheezing. The symptoms are not dissimilar to that of feline asthma or bronchitis. Other symptoms that may present themselves are very non-specific, such as changes in appetite, lethargy, and weight loss. This makes heartworm much harder to detect in cats.

Heartworm in ferrets

Ferrets are similar to dogs in that they are far more susceptible to heartworm than cats. Microfilariae levels found in the bloodstream of ferrets is typically around 50 to 60%, and they usually have low worm burdens.

Symptoms of heartworm in ferrets are very similar to those seen in cats with respiratory difficulties and fatigue being the most prevalent indications. However, like their feline counterparts, heartworm in ferrets is difficult to diagnose.

Diagnosing heartworm

Dogs suspected to be infected with heartworm are usually given an antigen test. This is a blood test that detects proteins that are released by adult female heartworms into the bloodstream of the host animal. However, this test cannot usually detect infections that are less than six to seven months old, because before this time, any microfilariae may not be fully matured.

Other methods of diagnosis include imaging, during which time X-rays or ultrasounds of your dog will be taken to determine if heartworms are present.

Heartworm is trickier to diagnose in cats and ferrets, and it is necessary to use a combination of blood tests and imaging to provide an accurate diagnosis of the disease.

Treating heartworm

The FDA has a number of approved heartworm treatments available for dogs, the majority of which use arsenic, which is effective at killing off adult heartworms. There are also several drugs that are able to eradicate microfilariae from your pet’s bloodstream.

While there are no treatments approved specifically for cats and ferrets infected with heartworm, your veterinarian may be able to prescribe treatments approved for other species under “extra-label drug use.” Talk to your veterinarian to discuss the best option for your pet.

Any treatment for heartworms also poses a risk to your pet due to the toxic nature of some of the ingredients, which have been known to cause life-threatening complications, including blood clots. Diagnosis and treatment can also be expensive due to the number of tests and comprehensive care your pet will require.

Prevention is better than cure!

As with most illnesses, prevention is almost certainly better than cure. There are a number of preventative treatments available via veterinarian prescription including injections, oral tablets, and topical liquids.

Pets older than six or seven months of age should be tested for heartworm before beginning preventative treatment while newborn animals can be treated right from their first vaccinations.

Speak to your veterinarian, who will be happy to advise you on the best course of preventative care for your pet.

Are humans at risk from heartworm?

Heartworm is spread via mosquitoes and is not contagious. In very rare cases, people can get heartworm after being bitten by an infected mosquito, but we do not make natural hosts, and any larvae usually die before reaching adulthood.