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Heartworm Season

Heartworm Season is Here

            With the weather getting warmer and the mosquitoes coming back out it is time to discuss the topic of heartworm disease. Heartworm disease is a potentially fatal disease in pets, caused by foot-long worms (heartworms) that live in the heart. Heartworm has adverse effects on the heart, lungs, and associated blood vessels of pets. Heartworm can affect dogs, cats, ferrets, wolves, foxes, and coyotes. Because undomesticated animals such as coyotes and foxes can get heartworm, they can become carriers, bringing the disease into more urban settings.

            Heartworm disease in dogs and cats presents itself very differently. In dogs, the worms live in the heart and mature into adult worms where they then mate and produce off-springs. Left untreated dogs can be the host to hundreds of worms which cause lasting damage to the heart, lungs and arteries. In cats, majority of heartworms do not survive into adulthood. Cats with heartworms typically have one to three worms as opposed to the hundreds that can live inside of a dog.  Heartworm in cats typically goes untreated, however, even immature worms can cause damage to the animal.

            Heartworm is transferred from one infected animal to a new host through mosquitoes. The adult worms mate and produces larvae, which is then circulated thought the blood stream. When a mosquito bites an infected animal, it takes up some of the larvae from the blood. After 10-14 days the larvae inside the mosquito becomes mature larvae. This infected mosquito then bites a new host and transfers the mature larvae to the new animal. Once in a new host it takes roughly 6 months for the larvae to mature and become an adult heartworm. Once mature, a heartworm can live for 5 to 7 years in dogs and 2 to 3 years in cats.

            In the early stages no signs or symptoms may be present. As the disease progresses clinical manifestations include persistent cough, activity intolerance, decreased appetite, and weight loss. If the disease is not treated it will progress into heart failure.  Dogs with a large number of heart worms can develop blockages of blood flow within the heart leading to life-threatening cardiovascular collapse.

            While heartworm disease tends to be more prevalent in regions with humid weather and large amounts of mosquitoes, all 50 states in the United States have seen cases of heartworm.  A dog that has traveled to an infected area can bring the disease into new parts where it can then begin to spread. For this reason, the American Heartworm Society recommends that you ‘think 12’: 1) get your pet tested every 12 months (done by an easy blood test), and 2) give your pet heartworm preventative 12 months a year. Puppies under 7 months can begin treatment without testing (takes 6 months for the worm to mature), but adult dogs over 7 months not previously on preventative but be tested before beginning preventative.

            Treatment for heartworm is commonly successful especially if it is caught early on. After confirmation of the disease the exercise of the animal will need to be restricted and the disease stabilized. Once everything is under control the treatment may begin. The more severe the stage of the disease the more likely for adverse complications. The severity of heartworm disease does not always correlate with the severity of the symptoms.

            Remember, think twelve. Get your dog tested every twelve months and talk to you veterinarian about placing your animal on the appropriate preventative for all twelve months out of the year.

Blog by: Nicole Lathrop


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