Heartworm Prevention

Lazy 5 Vets is ready to ensure that we protect your pet against this life-threatening infestation with heartworm prevention. Mammals are the primary species that can contract heartworm disease. Dogs, cats, and ferrets are all at risk, but many other mammals carry the disease including wolves, coyotes, foxes, and even sea lions. Foxes and coyotes may live near populated areas and are considered important carriers of the disease. Heartworms are a serious threat to your pet’s health and can be difficult to diagnose early on. That’s why prevention is key.

What Are Heartworms?

Heartworms are foot-long worms that live in the heart, lungs, and associated blood vessels of the affected pets. They can live between 5-7 years, and a dog can have as many as 250 worms in its system. Once the worms are in your pet’s system, they will begin reproducing.

Adult heartworms produce offspring called microfilariae. When a mosquito bites an infected pet, it will suck out blood that contains microfilariae. The microfilariae will mature inside the mosquito and become larvae. This step is necessary to spread heartworms. The microfilariae must have time to mature inside the mosquito before it can transmit them. After the microfilariae become larvae, they can then be transmitted through the bite of an infected mosquito to your pet.

Your pet is then infected by the young larvae. The larvae go through multiple stages of development inside your pet’s body tissue before migrating to the heart and lungs as adult heartworm. It takes about 6 to 7 months for the larvae to mature into adult heartworms. Once mature, the heartworms can live for 5 to 7 years in dogs, and 2 to 3 years in cats. Because of the worm’s longevity, each new mosquito can lead to an increasing number of worms inside a pet.

Heartworm Disease

Mosquitoes spread heartworms, so every area in the country has some risk of pets contracting heartworm disease. Transmission works through mosquitos only. Heartworms cannot be transferred any other way. A mosquito bites an infected animal and sucks out the infected blood with the microfilariae. It takes about 10 to 14 days for the microfilariae to mature inside the mosquito. After the microfilariae have time to mature into larvae inside the mosquito, they can then be transferred to another mammal in an infected mosquito bite.

While heartworm disease can affect any mammal, it is most common in dogs. The American Heartworm Society estimates that more than a million dogs in the U.S. have heartworm disease, and heartworms disease can be fatal and life-threatening. Dogs are considered a perfect carrier for heartworm disease, which means heartworms that live inside dogs mature into adults and produce offspring. If left untreated, the heartworm’s numbers can increase. Dogs have been known to harbor hundreds of worms in their bodies.

Heartworm disease is a life-threatening condition. The adult worms live inside the dog’s heart and lungs causing severe damage to the heart, lungs, and arteries. This will affect the dog’s health and quality of life long after the parasites are gone.

Cats are an atypical host for heartworms, and most worms do not survive to the adult stage. Cats with heartworm disease typically only have one to three adult worms living inside them, if that, and many cats only host immature worms. However, cats are still in danger of heartworm disease. Just because they are an atypical host does not mean that the worms will not infect them. In fact, heartworm disease can be even deadlier for cats and ferrets, as there is no known cure for them.

Symptoms and Signs

In the early stages of the disease, many dogs show no symptoms. The longer the infection persists, the more symptoms will show, and the more damage will be done. Early symptoms may include a persistent cough, reluctance to exercise, fatigue after moderate exercise, decreased appetite, and weight loss. As the disease progresses, pets (both cats and dogs) may gain the appearance of a swollen belly. This is from excess fluid building up from heart failure.

Dogs with a large mass of worms in their heart run the risk of sudden blockages and interference with their normal blood flow. This can lead to caval syndrome, a life-threatening form of cardiovascular collapse. Caval syndrome is marked by the sudden onset of labored breathing, pale gums, and dark, bloody, or coffee-colored urine. If your dog is experiencing any of these symptoms, get them to an emergency vet immediately. Few dogs survive caval syndrome without the prompt surgical removal of the worms.

Cats are not an ideal host for heartworms, and there is a chance that the disease may clear up on its own, however, it can leave the cat with lifelong damage, especially to their respiratory system. Blood clots can form in their lungs, and lung inflammation can occur when the adult worms die in the cat’s body.

Cats who have heartworm disease may show few symptoms, or their symptoms will be dramatic and noticeable. Symptoms may include coughing, asthma-like attacks, vomiting, lack of appetite, and/or weight loss. Some cats may have difficulty walking, experience fainting or seizures, or suffer from fluid accumulation in the abdomen. Heartworms in cats can affect their immune system and travel through the body to the heart, lungs, brain, eyes, and spinal cord. Unfortunately, the first sign in cats may be sudden collapse or death.

A Simple Solution

Heartworm disease treatment is expensive, long, and sometimes painful for the pet. It requires multiple veterinary visits and months of exercise restriction. However, prevention is easy, effective, and cheap. Sheldon Rubin, President of the American Heartworm Society 2007-2010 said, “For less than the cost of going to Starbucks for a weekly coffee, you can prevent heartworm disease in your dog. There are monthly pills, monthly topicals that you can put on the skin, and there’s also a six-month injectable product. The damage that’s done to the dog and the cost of the treatment is way more than the cost to prevent heartworm disease. A year’s supply of heartworm preventative will cost about $35 to $80, depending on a dog’s weight.”

Heartworm preventatives are only available with a prescription from your veterinarian. Many preventatives on the market not only prevent heartworms but may also protect pets from other parasites such as intestinal worms, fleas, ticks, and mites. Check with your veterinarian to see which preventative is right for your pet.

While there are drug-free options to reduce a pet’s exposure to mosquitos, there is no such thing as a “natural” heartworm preventative. No matter how much you reduce your pet’s exposure to mosquitos, it is imperative to give your pet a heartworm preventative. Even if you live in a part of the state that doesn’t have mosquitos, or only has them for part of the year, you still have to give your pet a monthly heartworm medication (unless you are doing the injection which should only be given by a veterinarian). This consistency is key to preventing heartworm in your pet.

The American Heartworm Society cautions pet owners about heartworm preventatives stating, “Heartworm preventatives work retroactively, eliminating new infections that were transmitted months earlier. Rather than guessing at when it might be ‘safe’, keep your pet on prevention year-round.” In as little as 51 days, heartworm larvae can mature into a juvenile/immature adult stage, which cannot be effectively eliminated by preventatives. Heartworm preventatives work by eliminating the young larvae stages before they mature, so a regular schedule is key to keeping your pet safe.

Have your pet tested yearly for heartworms! Do not skip testing. Even if your pet is on a year-round heartworm preventative, it’s important for your pet to get tested. While the preventative will likely keep your pet heartworm free, if you accidentally give them a dose late or if they spit it up, it opens a window of opportunity for infection. There is no way to tell what mosquito is infected, and mosquitos will bite anything that has blood, so there is no guarantee that your pet will not get infected. Subsequently, it takes up to 6 months for a dog to test positive after being tested, so if your dog gets infected, this yearly schedule should help with early diagnosis and treatment.

Early detection is key, which is why consistent testing is so important. The test just requires a small blood sample from your dog, and it works by detecting heartworm proteins. Testing for cats is more complicated, but normally just requires a small amount of blood. The blood sample will be screened for both an antigen and an antibody. The antibody test is used to detect heartworm larvae in the cat’s system. If your veterinarian does not feel that these tests are conclusive, they may order an x-ray or ultrasound.

All pets should be tested before being put on preventatives. Puppies and kittens can be put on heartworm prevention as well. Talk to your veterinarian about the right age to start your young pet on the right medication to ensure a long and healthy life!

What Happens if my Pet Tests Positive for Heartworm Disease?

For Dogs:

Most infected dogs can be treated successfully. The goal is to first stabilize your dog, then kill all adult and immature worms while keeping any side effects to a minimum. Once your dog tests positive, your veterinarian will want to confirm the test with an additional test. The treatment regimen for heartworm is expensive and complex, so your veterinarian will want to make 100% sure before started you and your dog on that path.

If both tests are positive, the first step is to restrict your dog’s exercise. This may be difficult, especially if you have an active dog, but physical exertion will increase the rate at which the heartworms cause damage in the heart and lungs. The worse your dog’s symptoms, the less activity they should be doing.

Before treatment can begin, your dog’s condition may need to be stabilized. In severe cases, or when a dog has another serious condition, this process can take several months. It’s important to make sure that your dog is stable before starting treatment to ensure their safety and long-term success of the treatment. Because symptoms can vary, stabilization therapy will also vary. Your veterinarian will advise you on what to do during this stage.

Once your dog is stable, your veterinarian will recommend a treatment protocol involving several steps. Dogs with no symptoms or more mild symptoms, such as cough or difficulty with exercise, have a high success rate with treatment. More severe cases can still be successfully treated, but the risk of complications increases. Please note that the severity of the disease does not always correlate with the symptoms, and dogs with many worms may not show symptoms early on.

Treatment will cause the worms to die. As the worms die, they break into small pieces, which can cause a blockage of the pulmonary vessels and cause death. It is imperative that while your dog is undergoing treatment and for several months afterward, they refrain from exercising. Studies have shown that exercise during treatment can be fatal due to the pieces of worms getting trapped in the blood vessels near the lungs and heart. Your veterinarian will advise you on when your dog can exercise again.

Approximately 6 months after treatment, your veterinarian will retest your dog to ensure that all heartworms are gone. To avoid contracting heartworm again, administer heartworm preventatives year-round for the rest of your dog’s life.

For Cats:

While there is a treatment for dogs, there is no approved treatment for heartworm infection in cats, so prevention is critical. If your cat tests positive for heartworm disease, don’t give up hope. There are still options.

Diagnosis of heartworm disease for cats can be complicated. While dogs can have over 30 worms in their bodies, cats generally have 6 or fewer. While the severity of heartworm disease in dogs is related to the number of worms in their system, in cats, even just one can make your cat very ill. Diagnosis can include a physical exam, an X-ray, a complete blood count, several types of blood tests, and an ultrasound.

As stated earlier, there is no approved treatment for heartworm disease in cats, and the drug used to treat heartworm disease in dogs is not safe for cats. Nevertheless, cats can often be helped with good veterinarian care. The goal is to stabilize your cat and determine a long-term management plan. For example, if your cat is not showing respiratory issues but worms were detected in the lungs, chest X-rays every 6 to 12 months may be recommended. Monitor your cat throughout their care and their long-term management plan. Cats with heartworms may experience spontaneous clearing of the worms, but the damage they cause may be permanent.

If the disease is severe, additional support and care may be necessary. Your veterinarian may recommend hospitalization to provide therapy, such as intravenous fluids, drugs to treat heart and lung symptoms, antibiotics, and other general care. In some cases, surgical removal of the worms may be possible.

Maintain your preventative schedule, even if your cat has a positive diagnosis of heartworms. Preventatives will keep new infections from occurring and will give your cat’s management plan a higher chance of success. Remember, both indoor and outdoor cats are at risk because of those pesky mosquitos.