Heartworm Disease: A big threat for dogs transmitted by a small insect

BrownDogIt’s springtime again and along with the warmer weather (OK, at least it’s supposed to be warmer) we’ll soon be seeing the emergence of mosquitoes. Besides being highly annoying little drones, they can also transmit a very dangerous parasite – the canine heartworm.  Heartworms cause a lot of damage and infestations can be fatal.  They used to be a problem almost exclusively in the south eastern United States, but their range has rapidly increased and the parasite has now been identified in all 50 states.  

The adult parasites live in the heart and major blood vessels of the lungs. They produce microscopic larvae which circulate in the dog’s blood stream. When a mosquito takes a blood meal, it will also ingest heartworm larvae, and when it bites another dog the larvae are transmitted,  Within 6 months the tiny larvae grow to be adults (8 to 10 inches) in the heart and blood vessels and the cycle begins again.

Early in the disease, the dog may not show any symptoms, but as it progresses, the heart is impaired and arterial walls are damaged.  Blood vessels may become blocked either by the worms themselves or by blood clots.  Blockage of large vessels can cause death, sometimes very suddenly. Signs of infection include coughing (sometimes bloody), weight loss, poor exercise tolerance, difficulty breathing, fainting and general wasting.  To complicate matters, heartworm larvae occasionally carry a parasite of their own known as Wolbachia which can exacerbate heartworm disease.

Treatment is available, but is expensive and can be risky especially if the pet is in an advanced stage and showing advanced signs.  During the course of treating for heartworms, veterinarians often concurrently treat with an antibiotic to kill the Wolbachia.

Fortunately, safe, effective medications are available to prevent the disease. Medication should be given once a month, year round.   Preventative medication kills larvae, but not the adults so it’s important to have a test for adults performed before starting a preventative medication and then, every year thereafter. Another benefit of giving heartworm preventative year round even outside of the mosquito season, is that almost all heartworm preventatives also prevent infestation by a variety of intestinal worms.

To find out more, go to:  www.heartwormsociety.org

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