 What is Heartworm Disease?
Heartworm disease is a serious health problem in many parts of the world. It is
caused by the roundworm, Dirofilaria immitis, a parasite
that lives in the heart and major arteries of the lungs. Yet, it is an
infection that can be prevented.
The Heartworm Life Cycle
Heartworms (Dirofilaria immitis)
have been found in a variety of wild and domestic mammals. Mosquitoes
carry immature forms of heartworm from an infected animal to a new
host by taking a blood meal from both animals. As the mosquito feeds from
the first animal, usually a dog, it picks up microfilariae (the offspring
of adult heartworms) as it engorges with blood. These microfilariae mature
in the mosquito, developing into infective larvae of D. immitis. When the mosquito subsequently bites another animal,
the larvae are introduced to the new host through the bite wound. The
larvae eventually make their way to the heart and associated blood vessels
by migrating through the body. Inside the heart they mature to adults and begin
producing microfilariae, completing the lifecycle. These new microfilariae
are then ready to be passed on to another dog or cat through the same process.
Are All Dogs at Risk?
Dogs
are the most commonly infected mammals and are considered the preferred
host of the heartworm. While the highest prevalence of heartworm infection
is in areas with heavy mosquito populations, heartworm-infected animals
can be found in all types of environments. The mobility of people and
our four-legged companions as well as the widespread prevalence of mosquitoes
make heartworm disease a health consideration no matter where you live. Ask your veterinarian for recommendations regarding diagnosing and preventing
this disease in your pet.
What Are the Signs of Heartworm Disease in Dogs?
The severity
and onset of clinical signs relate to 3 things: the number of worms, the
duration of the infection and the dog's response. Many dogs infected with
heartworms may not show any evidence of the infection in the early stages
of the disease. Signs can
eventually appear and will worsen with increased numbers of worms and
with lengthy infections, making early detection and prevention programs
an important part of managing your pet's health.
Initially
dogs tend to develop a cough and experience difficulty breathing. They
may also exhibit a decreased tolerance to exercise, develop fainting episodes
or suffer severe weight loss. Since the heart and lungs are affected,
many of the clinical signs seen or observed are typical of heart failure,
pneumonia or other debilitating diseases. Many
other less serious diseases can cause similar clinical signs, so it is
almost impossible to diagnose heartworm disease based on clinical signs
alone. A blood test is necessary to definitively diagnose heartworm infection.
How Do I Know if My Dog Has Heartworms?
Because most dogs in the early stages have no outward signs of disease, your veterinarian
will want to run a simple test for heartworm infection. Testing for heartworm
infection is routinely done in areas where mosquitoes live and the prevalence
of heartworm infection is high. The test itself requires a blood sample
from your dog, and can quickly determine if your dog has heartworms or
not. Blood antigen tests are highly reliable and
can be performed in the clinic while you wait for the heartworm status
of your dog to be determined.
My Dog Rarely Goes Outside; Can It Be Infected With Heartworms?
Dogs that
rarely go outside are at lower risk of becoming infected because of the
reduced exposure to mosquitoes. However, heartworm infections have been
reported in dogs that rarely go outside. Such infections may be caused
by infected mosquitoes that have gained access to the house. In addition,
most dogs make frequent short trips outside, during which mosquito bites
are possible.
When Do Veterinarians Recommend Testing for Heartworm Infection?
Veterinarians
recommend testing for heartworm infection before beginning heartworm preventive
medication, at regular intervals after the dog is on a preventive and
when dogs have clinical signs consistent with heartworm disease. In heartworm
endemic areas, testing is generally recommended as part of the annual
physical.
Can Heartworm Infection Be Prevented?
Fortunately,
heartworm infection can be prevented if preventives are started early
and are consistently given throughout the dog's life. There are a number
of medications available that prevent heartworm infection in dogs. However,
preventives will not eliminate an existing infection. Knowing the heartworm
infection status of your dog is an important part of keeping your dog
healthy and fit. We carry a number of different products to meet
the varying needs of our clients, including HeartGuard Plus monthly
chewables and Revolution.
What Can Be Done if My Dog Has Heartworms?
Medical
intervention is necessary to achieve a favorable outcome for the dog infected
with heartworms. Your veterinarian will choose a course of action that
will most effectively deal with your dog's disease and clinical signs. Medications to eliminate adult heartworms and immature heartworms are
available. Once successfully treated, preventives and regular monitoring
with a heartworm test should become part of
your dog's health maintenance plan.
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