What is it and Where Does it Come From?
Canine heartworm disease is a serious
and potentially fatal disease of dogs.
Mosquitoes are the only natural agents of
transmission. When a mosquito bites an
infected dog it takes up blood containing
immature heartworms called microfilariae,
which are larvae that incubate in the
mosquito for about 2 weeks. During this
time they become infective larvae. When
the mosquito bites another dog, the
infective larvae are passed into the second
dog, infecting it. The microfilariae migrate
through the tissues of the body for about
3 months, and finally enter the heart where
in another three months they reach adult
size. Adult worms grow up to 14 inches. A
dog can have several hundred worms in
his heart and major arteries.
Clinical Signs of Heartworm Disease
Adult heartworms reproduce and accumulate in the dog's heart and lungs. If not
removed,they can cause permanent heart
and lung damage, possibly death. The
important thing to remember is that a dog
can have serious damage and not show
clinical signs. Once the disease is advanced, the dog
may cough, have difficulty breathing,
tire easily, lose weight, and even collapse.
Without proper treatment, the disease can cause congestive
heart failure and even death.
Can Infected Dogs Be Treated?
With early detection, most dogs can be
successfully treated for heart worms.This
is one of the reasons that annual testing
is so important. Adult worms are killed
with a form of arsenic, which is given by
a series of carefully administered
injections. The worms die and are carried by
the blood stream to the lungs where they
lodge in small blood vessels. They
decompose and are absorbed by the body.
Heartworm treatment can pose a risk to
the infected dog; However, fatalities
resulting from treatment are rare. The patient should be given a thorough
physical and laboratory examination prior
to treatment. Any concurrent medical
problem that might cause complications
should be corrected before heartworm
After treatment, complete rest is important
to prevent lung damage from the
decomposing worms. Excitement and
exercise should be avoided for a least a
month, followed by a gradual return to
normal activity. After adult heartworms
are eliminated, another drug is given to
rid the bloodstream of microfilariae, the
larval forms which are not affected by the
drug used to kill the adult heartworms.
Testing For Heartworm Disease
The only way to detect heartworm disease
in the early stages is with a blood
test. Every dog should be tested annually
to make sure he is free from heartworm
disease. Testing should be done even if
he is on preventative medication since
infection can occur if for any reason a
preventative tablet was not properly
What Can You Do to Protect Your Dog?
Test your dog annually. If your dog is free
of heartworms, your veterinarian can
prescribe an appropriate preventative
medication. Interceptor, a new heartworm
preventative medication, not only
protects against heartworm disease, but
also against intestinal parasites - hookworms,
roundworms, and whipworms.
This added benefit is substantial, and for
this reason our hospital is now recommending
that dogs be given the preventative YEAR ROUND.
Berkshire Veterinary Hospital
730 1/2 Crane Avenue
Pittsfield, MA 01201