ED heart worm

[Gina Heitz <brier@oregonsbest.com>]

From Auntie Ellen

Note the wormer I sent home with you all was Heartguard brand and one of
the treatments outlined in my opinion should be used for all
puppies/dogs.

Gina

Heartworm Disease in the Pacific Northwest

This month’s column is in response to a question by a reader. Please
feel free to send in questions by phone, email or regular mail, and I
will be happy to research and answer your question.

Heartworm Disease can be one of the most dangerous of internal
parasites that a dog encounters because, as the name suggests, it affects
the heart.  The adult stage of the parasite, which can reach up to
31 cm in length, actually lives in the right side of the heart.  If
enough worms are present, they can cause heart blockage and heart
failure.  The parasite is present world-wide in temperate and
tropical climates, near populations of dogs, and is transmitted by
mosquitoes.

The adult worms living in the heart of an infected dog multiply by
producing microfilariae, which are much smaller, immature versions of
themselves.  These microfilariae circulate in the blood of the
infected dog.  When a mosquito bites an infected dog, it may draw a
small amount of the microfilariae along with the blood.  If this
happens, the microfilariae will undergo changes while living inside the
mosquito.  These changes take anywhere from 10 to 31 days. 
Once the maturation has reached a certain stage, the microfilariae
migrate to the mouth parts of the mosquito.  If this mosquito bites
another dog, the larvae will be deposited onto the skin and in the
wound.  The larvae gain entry into the bloodstream and then begin
another maturation process.  During this maturation process, the
larvae also being to migrate towards the thoracic, or chest, region, of
the dog.  By the time they are fully mature, which takes 3-6 months,
the larvae have worked their way into the right side of the heart.

The disease is easy to diagnose, as there are many tests available. 
However, it is not very simple to treat and the treatment itself can be
dangerous to the dog.  The worms residing in the heart must be
killed slowly, to allow the body to naturally dispose of the dead
worms.  If there are too many present, the dead worms themselves can
cause serious problems.  The immature larvae that are circulating in
the blood must also be killed, so that a new infection does not
occur.  There are several different treatments now available. 
Most involve 1-2 injections spaced several weeks apart with extensive
crate rest after the injections.

Prevention is by far the best method of controlling this disease. 
There are several different types of heartworm preventative available
through your vet.  The three main ones are Heartgard, Interceptorand
Sentinel.  They are given once monthly in the form of a chewable
treat, and prevent the disease by killing the microfilariae circulating
in the dog’s system before they can mature and reach the heart.  A
dog needs to be tested for the disease before being put on any of the
preventatives, as complications may result if the medication is given to
dogs who test positively.

Risk for this disease is greatly dependent on the region in which a dog
resides.  As many of you know, many parts of the mid-western United
States, as well as Texas, are considered endemic areas for
Heartworm.  The question remains as to whether or not Heartworm
disease is a significant risk in this area and there are differing
opinions.  The number of infected dogs in the Portland area is
extremely low, with slightly larger numbers in the eastern and southern
parts of the state.  Some experts believe it is only a matter of
time before Heartworm becomes more prevalent in the area. Others believe
that unless we get a significant weather pattern change, it will never
become a problem in this area.  So whether or not your dogs are on
preventative becomes a personal decision between you and your vet. 
In other areas of the country, it is much more clear when preventative is
needed.  One thing to consider is travelling with your dog. 
Check with your vet as to the prevalence of the disease in the area you
are going.

 From a personal standpoint… I keep all my dogs on heartworm
preventative.  My dogs take Sentinel, because it not only prevents
heartworm, but also controls the intestinal parasites roundworm,
hookworm, and whipworm, and it contains Program, which is a flea
preventative.  However, each of you must make your own decisions in
concert with your veterinarian.