With the return of Spring soon upon us we will be spending more time outdoors with our animal companions. This is an excellent time to discuss Heartworms!
Heartworms are actual worms that are a significant cause of infection and disease throughout our entire country. As dogs move around and with our lifestyles pushing further into wildlife territories we will continue to see Heartworm infections increase.
Dogs, including coyotes, wolves and foxes, are the natural host for Heartworms (Dirofilaria immitis). This means the worm goes through maturity into adulthood and can reproduce baby worms called microfilariae that circulate in the animal’s bloodstream. Cats and ferrets can also be infected (as well as some other mammals although it is less common) but are not considered a large reservoir of infective microfilaria.
The worms are transmitted when a mosquito feeds off of the blood of an infective host and ingests microfilariae which, over a 10-14 day period, go through three developmental stages. The third larval stage can be transmitted to another dog when the mosquito feeds on it. Within the new host, the larvae develop into sexually mature adult worms in about 6 months. At this time, the adult worms have set up camp within the dog’s lungs, heart, and associated blood vessels to begin the entire cycle again.
As more worms reproduce they continue to fill up the animal’s heart chambers. Heartworms can be 6-12 inches long and one dog can have hundreds of them! A heartworm infection can gradually lead to heart failure and even blockage of major blood vessels in an animal. The infection also provides more sources of contagion to the domestic and wild animal populations when mosquitos are out.
The main take-away is that Heartworm infection is completely preventable in dogs. There are several FDA-approved products your veterinarian carries and some even offer bonuses, such as prevention of flea, tick, mite or intestinal parasite infestation. Before starting a preventative regimen, your dog should be tested for heartworm if they are older than 6 months of age. If your puppy is younger than that you can begin heartworm prevention but still need to test in 6 months. The American Heartworm Society (heartwormsociety.org) recommends all dogs in the US be on annual heartworm prevention and continue to be tested for the disease on an annual basis.
Dogs with heartworm can be treated but the treatment is challenging and can be dangerous. A variety of factors affect the dog’s outcome such as the actual worm burden within the heart and also the dog’s activity level. There are no preventatives or treatments for cats or ferrets with heartworm disease.
Signs of Heartworm in dogs include a mild, persistent cough, lethargy, decreased appetite, weight loss and fatigue after moderate activity. Disease in ferrets progresses more rapidly because their hearts are so small. One heartworm in a ferret can be lethal.
Whether your dog has been on preventative in the past or not it is strongly advised that you start now, beginning with a heartworm test and repeating that annually, regardless of where you live. Ask your veterinary team now about testing, before you see the first mosquito!
