Although easy to prevent, heartworm disease continues to be a
major health problem for dogs living in the US and throughout
the temperate and tropical regions of the world. Since some dogs
can be infected for many years before symptoms develop,
heartworm disease in dogs may not be obvious. But, as heartworms
slowly cause damage to the pulmonary arteries of the lungs signs
of disease may include a mild persistent cough, reluctance to
exercise, fatigue after moderate activity, decreased appetite,
and weight loss. Eventually, as blood flow through the diseased
lungs becomes more restricted, some dogs can develop heart
failure. This is commonly recognized by a buildup of fluid in
the abdomen and the appearance of a swollen belly. Although less
common, a large number of heartworms can lead to a sudden
obstruction of blood flow through the heart and lungs. This
blockage often becomes a life-threatening form of cardiovascular
collapse and is referred to as "caval syndrome." Symptoms of
caval syndrome often include a sudden onset of labored
breathing, pale gums, dark red or coffee colored urine and an
ability or unwillingness to move. Without prompt surgical
removal of the heartworm blockage, few dogs suffering from caval
syndrome survive. Numerous blood tests are available for
detecting heartworm infections in dogs, and your veterinarian
will perform the test most appropriate for your dog. Keep in
mind that no diagnostic test can accurately detect all heartworm
infections. Tests cannot consistently detect infection until
heartworms are at least seven months old. Moreover, tests are
unable to detect infections if only male worms are present or if
there are only one or two female worms. At times, your
veterinarian may recommend the use of X-ray or ultrasound
imaging to help in the diagnosis of heartworm disease. They may
also repeat the blood test at suggested intervals. Annual
testing is recommended for monitoring the success of any
heartworm prevention program. Sometimes, individual risk
factors, clinical signs, preventive changes and in testing
limitations might warrant more frequent testing. The frequency
of testing should be discussed with your veterinarian, but all
dogs more than six months following initiation of or any lapse
in administration, and annually thereafter.
There are several things to consider once a dog is diagnosed
with heartworm disease. Without treatment, heartworm disease
will worsen and may lead to more serious illness. Unless medical
reasons identify a dog as a poor candidate, heartworm positive
dogs should be treated. However, treating dogs for heartworms
can also lead to serious health concerns, as the dead parasites
may cause further injury to the lungs and pulmonary arteries. A
thorough physical examination, radiographs, and blood and urine
tests may be needed prior to treatment to assess your dog's
level of risk. To reduce complications, your veterinarian will
educate you in great detail before beginning treatment. While
the heartworm medication mearsamine hydrochloride is extremely
effective in eliminating adult worms, some dogs will not be
completely cleared with a single course of treatment. Testing is
recommended six months after treatment to ensure all heartworms
were killed. If test are positive, additional adulticidal
treatment may be indicated.
Heartworm preventives are effective when given properly and on a
timely schedule. It is important to note that these medications
are quickly eliminated from a dog's body shortly after they are
given and do not continue to protect dogs from future infection.
Instead, they eliminate infections acquired since the last dose.
All approved heartworm preventives are highly effective, safe
and easy to use, are relatively inexpensive, and often provide
treatment for additional parasites. Prevention is always more
safe and affordable than treating dogs with adult heartworm
infections. Please remember, it is your responsibility to
faithfully maintain the program you have selected in
consultation with your veterinarian. The best way to eliminate
the risk of heartworm infection your dog is to institute a year
round prevention program.
Be certain to have all pets tested prior to initiating or
restarting any heartworm prevention program, as administration
of some preventives can cause life threatening reaction when
given to heartworm-infected pets.
