Heartworm disease is a serious and potentially fatal disease in pets…even here in Marathon County. Caused by foot-long worms (heartworms) that live in the heart, lungs and associated blood vessels of affected pets, heartworms cause severe lung disease, heart failure and even damage to other organs in the body.
Your dog is a natural host for heartworms. Heartworms which live inside a dog mature into adults who mate and produce offspring. Left untreated, their numbers increase. Dogs have been known to harbor several hundred worms in their bodies. Heartworm disease causes lasting damage and can affect the dog’s health and quality of life long after the parasites are gone. Prevention is the best option, and treatment, when needed, should be started as early in the course of the disease as possible!
The mosquito is a key player in this heartworm debacle. Adult female heartworms living in an infected canine(including wolves, foxes, and coyotes) breed and produce microscopic baby worms called microfilaria that circulate in the bloodstream. When a mosquito bites and takes a “blood meal” from an infected animal, it picks up these baby worms, which develop and mature into “infective stage” larvae over a period of 10 to 14 days. Then, when the infected mosquito bites another dog, cat, or susceptible wild animal, the infective larvae are deposited onto the surface of the animal’s skin and enter the new host through the mosquito’s bite wound. Once inside a new host, it takes approximately 6 months for the larvae to mature into adult heartworms. Mature heartworms can live for 5 to 7 years in dogs
In the early stages of the disease, many dogs show few symptoms or no symptoms at all. The longer the infection persists, the more likely symptoms will develop. Active dogs, dogs heavily infected with heartworms, or those with other health problems often show very pronounced clinical signs. Signs of heartworm disease may include a mild but persistent cough, reluctance to exercise, fatigue after even moderate activity, decreased appetite, and weight loss.
As heartworm disease progresses, pets may develop heart failure and the appearance of a swollen belly due to excess fluid in the abdomen. Dogs with large numbers of heartworms can develop sudden blockages of blood flow within the heart leading to a life-threatening form of cardiovascular collapse. This is called caval syndrome, which shows up as a sudden onset of labored breathing, pale gums, and dark bloody or coffee-colored urine. Without prompt surgical removal of the heartworm blockage, few dogs survive.
Heartworm disease is a serious and progressive disease. The earlier it is detected, the better the chances the pet will recover. There are few, if any, early signs of disease when a pet is infected with heartworms, so detecting their presence with a heartworm test administered by a veterinarian is important. The test requires just a small blood sample from your pet, and results are obtained quickly. If your pet tests positive, further tests may be ordered.
All dogs should be tested annually for heartworm infection, and this can usually be done during a routine visit for preventive care. Here are some guidelines on testing and timing…CONSULT YOUR VETERNARIAN!
Puppies under 7 months of age can be started on heartworm prevention without a heartworm test (it takes at least 6 months for a dog to test positive after it has been infected), but should be tested 6 months after your initial visit, tested again 6 months later and yearly after that to ensure they are heartworm-free.
Adult dogs over 7 months of age and previously not on a preventive need to be tested prior to starting heartworm prevention. They, too, need to be tested 6 months and 12 months later and annually after that.
If there has been a lapse in prevention (one or more late or missed doses), dogs should be tested immediately, then tested again six months later and annually after that.
NEVER JUST TAKE IT UPON YOURSELF TO BEGIN ADMINISTERING HEARTWORM PREFENTATIVES WITHOUT CONSULTING YOUR VETERINARIAN FIRST!
Annual testing is necessary, even when dogs are on heartworm prevention year-round, to ensure that the prevention program is working. Heartworm medications are highly effective, but dogs can still become infected. If you miss just one dose of a monthly medication—or give it late—it can leave your dog unprotected. Even if you give the medication as recommended, your dog may spit out or vomit a heartworm pill—or rub off a topical medication. Heartworm preventives are highly effective, but not 100 percent effective. If you don’t get your dog test, you won’t know your dog needs treatment.
No one wants to hear that their dog has heartworm, but the good news is that most infected dogs can be successfully treated. The goal is to first stabilize your dog if he is showing signs of disease, then kill all adult and immature worms while keeping the side effects of treatment to a minimum.
If your dog does test positive, here is what you can expect:
- Once a dog tests positive on an antigen test, the diagnosis should be confirmed with an additional—and different—test. Because the treatment regimen for heartworm is both expensive and complex, your veterinarian will want to be absolutely sure that treatment is necessary.
- It is imperative to restrict exercise! This can be hard to do, especially if your dog is accustomed to being active. But your dog’s normal physical activities must be restricted as soon as the diagnosis is confirmed, because physical exertion increases the rate at which the heartworms cause damage in the heart and lungs. The more severe the symptoms, the less activity your dog should have.
- Before actual heartworm treatment can begin, your dog’s condition may need to be stabilized with appropriate therapy. In severe cases of heartworm disease, or when a dog has another serious condition, the process can take several months.
- Once it is determined that your dog is stable and ready for heartworm treatment, your veterinarian will recommend a treatment protocol involving several steps. The American Heartworm Society has guidelines for developing this plan of attack. Dogs with no signs or mild signs of heartworm disease, such as cough or exercise intolerance, have a high success rate with treatment. More severe disease can also be successfully treated, but the possibility of complications is greater. The severity of heartworm disease does not always correlate with the severity of symptoms, and dogs with many worms may have few or no symptoms early in the course of the disease.
- Approximately 6 months after treatment is completed, your veterinarian will perform a heartworm test to confirm that all heartworms have been eliminated. To avoid the possibility of your dog contracting heartworm disease again, you will want to administer heartworm prevention year-round for the rest of his life.
Dogs at HSMC may be tested for heartworm disease prior to adoption for a $20 test.