Counter Surfers Unlimited
Labsr4U Pawsitive Advice
Heartworm - Article 1
The following article was written by Linda Oldham
The heartworm originally was pretty
well confined to the southeastern Atlantic and Gulf Coasts state in the
US. Our mobile society has effectively spread it to almost all parts of
the country.
Mosquitoes are the conduit for the disease. The mosquito picks up larvae
from an infected animal, carries it in its mouthparts and when it bites
a dog, the larvae enter the dogs skin. The larvae burrow beneath the
skin and eventually evolve into small immature worms. The process from
bite to immature worms takes about 70 days. Only during the first 12
days after the larvae enter the dog's body are they susceptible to the
killing effects of diethylcarbamazine (the orig. daily HW preventative).
Through the second and third stages of life in the dog, the larvae are
susceptible to two other drugs, ivermectin and milbemycin. These are the
basis of the monthly HW preventatives.
Immature worms make their way in to a vein and are carried to the right
ventricle of the heart and the pulmonary artery where they grow further.
About 6 months after entering the dogs body, the worms fully mature.
Adults can reach lengths of 4 to 12 inches and live up to 5 years. As
many as 250 worms can be found in a heavily infested dog.
The adult worms eventually clog the heart to such an extent that the
heart cannot beat or pump blood normally and, without preventative or
treatment intervention, the dog will die because the heart will fail.
The worms can also migrate into the right atrium of the heart and into
the superior and inferior vena cavae and the veins of the liver.
Worms in the pulmonary circulation can migrate to the ends of the
pulmonary arteries where the can stop blood flow and cause clotting,
called pulmonary thromboembolism.
Reproduction occurs, if worms of the opposite sex are present. One
female can give birth to live young called microfilaria (what is seen in
the blood when a dog tests positive). 5,000 microfliariae can be
produced in one day by one female worm.
One day a mosquito bites an infected dog, picks of the larvae and
carries it to an uninfected dog, infects that dog by the simple process
of biting. And so it goes.
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