Detecting Heartworms Can Be Difficult In The Initial Stages
As Many Dogs Show No Symptoms
immitis (heartworms) are one of the most insidious and
deadly worms. Heartworms can infect many species, including cats
and humans, but dogs are particularly susceptible.
Heart worms are introduced into the host through mosquitoes that
are infected with heartworm larvae. Once a mosquitoe has biten
the dog the larvae take 6 - 7 months to develop into sexually
mature male or female worms. Even as immature adults they can
begin to reproduce and the females release microfilariae into
the bloodstream. Microfilariae are a prelarval stage of heartworms
(pronounced: micro fil ar ee).
This is how the life cycle continues. At this point if the dog
were to be bitten by a mosquitoe the mosquitoe would become infected
with microfilariae in the blood. That mosquitoe could then go
on to infect another animal.
Heartworms take about a year to become fully mature adults. Males
grow to 4 - 6 inches while females get to be 10 - 12 inches long.
Detecting the presence of heartworms can be difficult in the
initial stages as many dogs show no symptoms. This is more true
of dog breeds that are less active. This is because the heartworm
works its way into the lower lungs and eventually the right ventricle
of the heart.
Since Australian Shepherds are so active changes caused by heartworms
to the functioning of lungs and heart will show up sooner and
with fewer worms present than in more sedentary breeds.
As the infestation progresses symptoms will escalate, beginning
with a cough then greater intolerance for exercise with unusual
sounds from the lungs and difficulty breathing. Temporary loss
of consciousness can occur as the flow of blood to the brain is
Enlargement of the liver, fluid build up in the abdomen and unusual
heart sounds are some of the less obvious symptoms that can occur.
Unless treated a heartworm infection can lead to eventual death,
usually from heart failure. If heartworms make their way into
the caudal vena cava, a large vein between the liver and the heart,
sudden collapse and death due to Liver Failure Syndrome can result
within two or three days. Surgical intervention to remove the
worms is required in this situation.
Fortunately treatment for heartworm is most often successful.
Treatments are designed to eliminate both the adult worms and
the prelarval microfilariae. A far better and more economical
approach to dealing with heartworm is prevention.
Consult with your vet to determine the best approach and to develop
an effective schedule.
Australian Shepherds can have drug sensitivities as they frequently have a mutation of the MDR1 (Multi Drug Resistance 1) gene. This commonly causes toxicity from ivermectin an ingredient found in heartworm medications. It is always advisable to consult with your veterinarian before giving your Aussie any medications. Even over-the-counter medications can be toxic due to this increased sensitivity.
More information about Ivermectin and
other drugs that can be dangerous
for Australian Shepherds here.
Dr. Andrew Jones, DVM
Dr. Andrew Jones
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