Heartworm: The importance of prevention

by A. Tosone

Ask any local veterinarian and they will tell you that your pet should be on preventative medicine for heartworm. No questions asked. It’s imperative. Even life saving.

But what exactly is heartworm? Heartworm is a parasite that lives in the heart and pulmonary arteries of its host. The parasite takes about 5 to 7 months to mature to its adult form so infection is rarely detected in an animal that is under a year old. Both dogs and cats (and some other wild animals) can be infected, although dogs are more commonly diagnosed. Once mature, the adult worms clog the heart and blood vessels leading from the heart. Thus, the heart strains to function at normal capacity and supply the rest of the body with proper blood flow. Lungs, liver and kidneys are particularly susceptible to damage from reduced blood flow due to heartworm infection. Transmission of the disease occurs from animal to animal via mosquitoes so potential hosts living in hot, humid climates are at highest risk of infection.

Symptoms of heartworm infection can vary depending on the number of adult parasites living in the host. Generally speaking, weight loss, labored breathing, coughing, fatigue/loss of stamina and vomiting are signs of infection. Light to moderate exercise can become difficult and often exacerbates symptoms. Unfortunately, by the time symptoms manifest themselves, infection is usually quite advanced. Heartworm infection is diagnosed by routine exams and blood tests performed by veterinarians. Other diagnostic measures may include x-rays or ultrasound.

Treatment of heartworm infection carries risk and, in rare instances, the treatment itself may prove fatal. In recent past, drugs used to treat heartworm disease contained high levels of arsenic and often had multiple harsh side effects. Today, a newer drug has fewer side effects, increasing successful treatments. Adult parasites and larvae are killed in separate treatments. Adult heartworms are killed with an injectable drug, which may be administered in several injections 30 days apart. As the parasites die, they break apart and travel from the heart region to the lungs where they may take several weeks to be fully reabsorbed by the body. Most post-treatment complications are caused during the re-absorption period by the parasite fragments. The patient must undergo treatment to kill immature parasites approximately one month after treatment for adults is complete. Treatment for bacterial infection (caused by bacteria carried by the worms) may be administered in conjunction with the heartworm treatment. With all treatments, exercise must be drastically limited. Animals with severe heartworm infection may also require special diets, pain relievers, medication to help remove fluid from lungs as well as medication to improve heart function. In some cases, the life span of an infected animal may be shortened even after treatment if the infection was severe and permanent damage to the heart and other organs occurred.

Prevention of heartworm infection takes less of a toll on your pet’s body and is less expensive for your budget. Each year, your pet should have their blood tested by your veterinarian. If clear of infection, preventative medicine is prescribed by your vet at a minimal cost. Doses are given on a monthly basis and typically come in a flavor your pet will find appealing (perhaps beef or liver flavored). Most vets recommend giving heartworm preventatives year-round as apposed to just when mosquitoes are highly active and abundant (typically from the onset of spring to the first frost). The benefit to year-round heartworm prevention is that the drugs used to prevent heartworm disease also may prevent infection of some other intestinal parasites. Taking all things into consideration, unless you live in Alaska (the only state where heartworm is not found), the old adage is true: prevention is the best medicine.

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Found Chicago, NFP is a 501(c)3 no-kill, all-breed rescue that serves to rescue, rehabilitate and re-home the most medically and behaviorally challenged dogs that would otherwise be euthanized. Found Chicago Boarding & Training Center is a subsidiary of Found Chicago, NFP that provides services to the public to give dog owners the knowledge they need to better handle their dogs and improve the quality of the dog-human relationship. All proceeds from services offered through Found Chicago Boarding and Training Center wholly benefit the dogs we rescue, rehabilitate and re-home.

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