Byron Pet Clinic

25 Frontage Road NE
Byron, MN 55920


Canine Heartworm Disease


Heartworm is a disease caused by a parasitic worm, called “Dirofilaria immitis,” that generally lives in the arteries of the lungs and the right side of the heart of dogs, cats and other species of mammals. Dogs of any age and/or breed are susceptible to this serious and potentially fatal disease.


Heartworm is transmitted from one animal to another by mosquitoes.  Small immature heartworms, called microfilaria, (produced by the adult worms) are found in the blood of infected dogs. When taking a blood meal from an infected host, the mosquito ingested the heartworm microfilariae, which then develop in the mosquito.  The mosquito then feeds on another dog, and deposits the infective larvae, which enter the tissues through the bite wound. Over the next 6 months, the larvae migrate through the dogs’ tissues and mature in the heart and lungs. The male heartworms (four to six inches in length) and the females (10-12 inches) become fully grown about one year after infection, and their life span in dogs averages up to five to seven years.


Many dogs may not show signs of heartworm infection in the early stages.  As the burden of heartworm accumulates over the course of months to years, dogs may develop a cough and have a difficult time breathing. Decreased tolerance to exercise, severe weight loss, lethargy, and reduced appetite may also be seen. The severity of onset depends on multiple factors including the number of heartworm, the duration of infection, and the dog’s response.


There are many laboratory tests that can detect and help aid in the diagnosis of canine heartworm; these include blood tests, radiographs, and ultrasound. Routine testing for heartworm infection is recommended to ensure proper treatment and prevention for your pet. Your pet should be tested prior to starting heartworm preventative medication, and at regular intervals throughout your pet’s life. How often the intervals for testing are depend on your pet’s lifestyle and preventative plan. Ask your veterinarian what is best for your pet.


Because heartworm has been reported in all 50 states even in dogs that rarely or never go outside, prevention is the best option for your pet.  Heartworm prevention is safe, easy and inexpensive.  While treatment of the disease is possible, it is a complicated dangerous, and expensive process, which can take weeks for an infected animal to recover. There are a variety of options for preventing heartworm infection in dogs; these medications interrupt heartworm development before adult worms reach the lungs and heart causing disease. Heartworm preventatives include a variety of monthly tablets or chewable that also have medications to control more common intestinal parasites and even fleas, you can find a product to fit your pet’s needs. These methods are extremely effective, and when administered properly and on a timely schedule, heartworm infection can be prevented.

With warmer weather just around the corner, it is time to start thinking about your dog and his/her heartworm prevention plan. Please call us at 507-775-6738 to set up your pets heartworm test, order heartworm preventatives, or discuss your pets prevention plan.


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