Canine Heartworm disease is caused by a small thread-like worm that can grow up to six inches long in the right side of the heart. Once infected by this parasite, damage begins to both the heart and lungs of the affected dog. Heart failure or severe scarring of the lungs typically leads to death within a few short years. Heartworms have two hosts and need both to spread. The cycle begins in the right side of the heart where male and female worms mate and produce offspring who travel with the blood. When a mosquito bites an infected dog it ingests the small larvae. The parasite then undergoes two molts and develops further within the mosquito. At this point, the parasite is ready to travel back to its main host, our canines. Once a dog is bitten by an infected mosquito it typically takes three to four months for symptoms to appear and disrupt pet health. The most important fact to remember is that dogs cannot infect other dogs; the parasite needs mosquitoes to complete its journey to adulthood.
Once our pet health is infected by these parasites, the heart can have a hard time pumping blood around the worms and into the lungs. The heart has to work harder to get the proper amount of blood to the lungs. Like other muscles, the heart tends to get larger over time with this increased strain. An enlarged heart is bad because it is thicker and so it can store less blood to pump out so it has to work even harder, making it enlarge even more. This process is a vicious cycle that will only lead to heart failure. Typically it usually takes two to three years for the full process to take place. Along with the heart disease it also causes irritation in the arteries leading to the lungs causing scarring of the lung tissue. This damage leads to a decrease in the ability to transfer oxygen to the blood.
Every year veterinarians see more and more animals testing positive for heartworms, some with physical symptoms and some without. Back in the eighties and early nineties the treatment of choice was basically arsenic, which had devastating affects on pet health. The problem with treating heartworms is that you want them to die very slowly so that the bodies’ immune system has time to slowly breakdown the worm. If they die fast they can loose their grip within the heart and get lodged within the lungs causing severe damage and acute death. The goal today is a very slow kill over approximately three months. The new medication is called melarsamine which is given over two injections. This is followed up about a month later with another medication called ivermectin which kills larval or “baby" heartworms. It is very important not to give the ivermectin first because it causes a fast kill of adults leading to the same acute death that occurred in the past. Most veterinary hospitals discuss with owners of heartworm infested pets a four-month treatment plan all leading up to a retest where, hopefully, the pet will be cleared of the parasite.
Any vet will tell you that much better than heartworm treatment is heartworm prevention. Heartworm preventatives are a prescription only medication that can be obtained through your local veterinarian and can save your pet health from the first application. It is important to make sure you pet is current on its heartworm test before the purchase of the prevention because once again if your pet is positive the preventative can actually cause death of your beloved canine. If your pet has been off heartworm prevention any more than two to three months you should get your pets retested before starting the medicine again. Even if they are indoor dogs, they can still get infected. The truth is that mosquitoes come inside the house every time we open and close the doors and they bite both us and our pets. In addition to heartworms, the heartworm prevention also controls most of the intestinal parasites that our pets carry. The more dogs that are on heartworm prevention the less likely mosquitoes can contract the parasite and the further it spreads.
Gary Pearson is an accomplished niche website developer and author.
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