Heartworm signs (Dirofilara immitis ) are consistent with worms
infecting both the heart and
the lungs. Clinical signs or symptoms are not visible during the early
stages of the disease and only start as the size of the infestation
begins to grow in the heart. The most damage is done to the
lungs, only damaging the heart during the later stages of disease. Dog
Heartworm symptoms usually starts with a soft cough. Other symptoms of
canine Heartworm includes
fatigue, reluctance to engage in physical activity, weight
loss and loss of desire to eat. As the disease develops the
cough can worsen, including the production of blood. Signs associated
advanced stages of the disease include vomiting, gagging and
respiratory problems such as rapid breathing. If left untreated, dog
Heartworm disease can cauase death. All dogs must be tested for
Heartworm disease before treatment begins."
Heartworm signs occur well after a dog has contracted the disease.
It is spread from dog to dog by mosquitoes who spread the
larvae of the worms when feeding on a dog's blood. Because of
the way it is transmitted, it is a problem during mosquito
Heartworm signs include
an initial soft cough followed by symptoms such as weakness, weigth
loss and problems with activity. As the canine Heartworm
disease progresses, symptoms include appetite loss and even collapse.
Source: Cornell University , College of Veterinary Medicine, Baker
canine Heartworm disease is possible and effective, although it can be
dangerous since the treatment
kills worms that are present in the heart and potentially the lungs.
It is not uncommon to find 30 worms inside a dog. For this
reason, veterinarians recommend 1x month medications to
prevent the problem in areas where mosquitoes reside, or at minimum
during peak seasons.
Initially, dogs that have heartworms do not show any sign of disease.
When they do show signs it is difficult to differentiate
these signs vs. other common canine diseases.
Canine Heartworm symptoms start to appear when a dog becomes heavily
infected. A syndrome called vena cava occurs when the heartworms enter
the heart and enter into the part of the heart called the vena cava.
Heartworm signs initially
- Cough (mild, persistent)
- Blood in the sputum when coughing
- Doesn't want to exercise
- Appetite loss
- Weight Loss
Heartworm signs in later stages of the infection:
- Difficulty breathing
- Pale Gums
- Desire not to move
- Blood of darkened urine (severe cases called Caval Syndrome
which is a form of liver failure)
Heartworms in the
ventricle of the heart of a dog
Source: Washington State University/From the collection of Dr. Richard
Dog Heartworm Diagnosis
only way to be certain that a dog has Heartworms is to do a blood test
which measures antigen levels (ELISA is a common type of test).
Tests can't detect Heartworms until 6 - 7 months after
infection. If tests are conducted to early, a false reading
may be obtained, meaning the test says a dog doesn't have a Heartworm
problem, when it actually does. A Knott's test is used to isolate any
of the Heartworm larvae.
Dogs are tested before Heartworm medications are refilled to
ensure that they are Heartworm free. Even when dogs receive
Heartworm treatments, any missed doses could result in a problem,
particularly if a dog doesn't swallow a tablet. If Heartworm develops
and a dog is given a preventative, it could be a problem since worms in
the body will die potentially causing problems. The
growth stage of the
Heartworm also will dictate the type of medication needed.
To determine the severity of the Heartworm signs and condition, x-rays
are used. Echocardiography, another test of heart function, can also be
Treatment for canine Heartworm is effective, even during
advanced stages of the disease. A medication called an
Milarsomine dihydrochloride) is used to kill the heartworms.
It is administered via injection deep into a muscle. Most
veterinarians prefer to keep a dog in the veterinary
hospital during the treatment period. Once home, dogs need
restricted exercise for 4 to 6 weeks as the dog Heartworm signs subside.
If the heartworms signs are severe such as the sudden onset of lethargy
or weakness, due worms that are blocking the flow of blood, the surgery
is needed. This condition is called caval syndrome.
The surgery is performed with local anesthesia with Heartworm
signs subsiding in 12 to 24 hours.
Heartworm signs and infection are completely avoidable by providing
a 1x a month treatment. Products available are
safe and widely used. These include Heartgard
Each is administered
orally and come in a chewable form. Revolution
the form of a topical which is applied to the small of the a dog's back
1x a month.
In the case of Heartgard, Interceptor and Revolution,
they each help to prevent infections caused by other worms such as
roundworms and hookworms. Sentinel helps to prevent fleas.
Active ingredients in these products are Ivermectin,
milbemycin oxime and moxidectin.
Another product, Proheart
6, is given by injection every 6 months.
This product only protects against Heartworm.
During the time of year when mosquitoes are not biting such as winter,
a veterinarian may not recommend the use of a preventative with the
highest risk months being May - October in Northern states.
Darkened areas of the map below indicates the severity
of Heartworms in the United States:
Puppy Heartworm prevention starts at 8 weeks of age.
A homeopathic or natural product called
Parasite Dr. Capsules
, is also available. While
not a preventative, it contains natural ingredients that provided added
support for helping to expel parasites such as worms.
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American Heartworm Society
of Veterinary Medicine