What is Heartworm Disease?
Dr. Abigial Brady
Heartworm disease is very common in North Carolina and has been diagnosed in all 48 states within the continental US. Heartworm disease is a fatal disease in dogs and cats. Heartworms are spaghetti-like worms that live inside the heart of dogs, cats, and wild mammals such as wolves, coyotes and foxes. When the worms are living in the heart they can cause heart failure, lung disease and severe disease in other organs of the body.
How do our pets get heartworms?
Heartworms are spread through mosquito bites. Wild animals are natural carriers of heartworms. When a mosquito bites an infected animal, they ingest the heartworm larvae (immature heartworms). The larvae mature into the infective stage while inside the mosquito. When the mosquito moves on and bites the next dog or cat they come across, they transfer the larvae into the pet. The immature mosquitos then migrate from the bite into the bloodstream and then to the heart, where they will continue to mature and cause signs of disease. From the time of the bite to the time that the worms are matured and able to be detected by a blood test is an average of 6 months.
Dogs are a natural host of the heartworm, meaning that the worms can mature and reproduce in the heart. Because of this, the worms can continue to reproduce and there can be up to several hundred worms living in one dog if they are left untreated. The heartworms can live in the dog for 5-7 years.
Cats are not natural hosts of heartworms. This means that they rarely develop to adulthood and typically do not reproduce. Normally when a cat is infected with heartworms, there are only 1-3 worms present. Even though they rarely have adult worms and in comparison to dogs, there are only a few present, heartworm disease can still be severe and even fatal in cats. The heartworms can live in the cat for 2-3 years.
What are the signs of heartworm disease?
In heartworm positive dogs, the most common signs seen are associated with heart disease. In early stages of disease there are usually no clinical signs that you will be able to detect. The most common signs that are seen by owners include a persistent cough, reluctance to exercise, becoming tired/worn out more quickly, weight loss and loss of appetite. In late stages of disease or severe disease you may see a distended abdomen, collapse, labored breathing or pale gums.
Cats with heartworm disease may have no signs or very severe signs. They commonly have respiratory signs including coughing or asthma-like breathing but they may also have vomiting, loss of appetite, weight loss, difficulty walking, fainting or a distended abdomen. Unfortunately in cats the first sign may be sudden collapse or even sudden death.
How do I get my pet tested for heartworms?
All dogs should be tested for heartworms every 12 months (starting at 1 year of age). This can be done with the annual blood work that your veterinarian runs. There are in-hospital, rapid tests that can be run, or your veterinarian may elect to send your pet’s blood to an outside lab to run a heartworm test.
Because cats do not usually have adult heartworms, they can be more difficult to detect. The preferred method to test cats is to took for both the antigen and antibody (the presence of worms and the exposure to them) but your veterinarian may also recommend x-rays or an ultrasound to help detect the worms if your cat is showing clinical signs of heartworm disease.
How can I prevent heartworm disease?
There are many veterinary approved heartworm preventions on the market. There are some preventatives that you may be able to find over the counter but these medications are not regulated so please consult your veterinarian before starting your pet on one. Heartworm prevention is available in many forms. There are several brands of oral medications, both pills and chewable “treats”. You can also purchase topical liquids, which can be convenient for picky eaters or pets with food allergies. Most preventatives should be given monthly, 12 months a year. Many of the available preventatives also protect pets from intestinal parasites and fleas, ask your veterinarian for more information on this!
How is heartworm disease treated?
In dogs there are a few different protocols that are available to treat heartworms. Before treatment is performed, many diagnostic tests such as blood work and x-rays will be done to make sure your dog is getting the best care. Your veterinarian will come up with the best treatment protocol for your dog, most of which include several visits to the veterinary hospital, strict exercise restriction and close monitoring. Treatment can be very difficult on a dog’s body and there are side effects that can occur, but without treatment heartworm disease can be fatal. The treatment protocols can be several hundred to a couple thousand dollars. Monthly prevention is very important. The cost of prevention is much less than the cost of treatment and is much easier on the dog’s body.
Unfortunately for cats there are no approved drug protocols. Strict monitoring and close veterinary care is crucial to maintaining your cats health if they are diagnosed with heartworm disease.
Please talk to your veterinarian about any questions you still have about heartworms and how to protect your pets. The American Heartworm Society also has an abundance of information on their website.