Dirofilaria 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. Detecting heartworms can be difficult in the initial stages as many dogs show no symptoms.
Heart worms are introduced into the host through mosquitoes that are infected with heartworm larvae. Once a mosquito 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 pre-larval 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 mosquito the mosquito would become infected with microfilariae in the blood. That mosquito 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.
Owners: Susan and Chris Huber, Photo: Petra
This is my blue merle Aussie, Jackson, at Walchensee in Germany. He loves to swim at Walchensee Lake.
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 interrupted.
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.
Read more about the MDR1 Gene Mutation that can cause a dangerous sensitivity in Aussies to many medications.
Fortunately treatment for heartworm is most often successful. Treatments are designed to eliminate both the adult worms and the pre-larval microfilariae. However, Australian Shepherd owners need to be aware that many drugs available for treating heartworms can be extremely dangerous for Aussies due to a common genetic defect. Learn more about the MDR1 gene mutation here.
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.
For more information about Aussie health issues see the Australian Shepherd Health & Genetics Institute (ASHGI).
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