How Do Dogs and Cats Get Heartworm Disease?

How Do Dogs and Cats Get Heartworm Disease?

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Heartworm disease can potentially be fatal to your beloved dog. Learn how a single bite from a mosquito can put your dog at risk.

Heartworm disease can be transmitted through one method alone: the bite of a mosquito. Whether the new host is a dog, cat, or in rare cases, a human, the parasiteโ€™s only means of spreading into the bloodstream is through these pests.

Heartworms in Mosquitoes

Mosquitos contract heartworm microfilaria when they bite infected dogs. The microfilaria then undergoes an incubation period inside the mosquito for up to two weeks. During this time, the infected mosquito cannot spread heartworm disease. But when the microfilaria have developed into infective larvae, they move back into position by the mosquitoโ€™s mouth so that when the mosquito bites another dog, the larvae can move into the next dogโ€™s tissue. There is no way to tell if a mosquito is carrying heartworm disease, or if they are prime to pass on infective larvae.

Transmitting Heartworm Disease to a Host

Once the larvae pass through the dogโ€™s skin under the mosquito bite, they grow for up to two weeks under the tissue. After they have developed to the next larval stage, they move to the dogโ€™s chest and abdomen muscles until they molt once again, up to two months after the initial bite. Finally, the larvae enter the bloodstream and molt and grow as they travel to the heart and surrounding vessels. These mature heartworms have been in your dogโ€™s system for up to four months.

If one pet has heartworm disease, it doesnโ€™t mean your other pets will become infected with the parasite. Because heartworms can only be transmitted through an infected mosquito bite, dogs and cats that share a common space will not transmit the disease to each other. Even if a mosquito bites the infected pet and then an uninfected pet, the microfilaria will not have enough time to incubate and pass along to its next host. Only a mosquito previously infected with incubated heartworm disease will be able to transmit it.

Are Dogs in States With Lower Mosquito Populations at Risk for Heartworm Disease?

Though areas with smaller mosquito populations may seem safe from this disease, cases of heartworm in pets have been found in all 50 states, including Alaska. Giving your pets heartworm prevention medication, like Revolution, Heartgard Plus Chewables, or Iverhart Max for dogs, is the best way to make sure your pets avoid contracting it no matter where you reside. You can also administer Interceptor Plus for dogs which prevent both heartworms and intestinal worms.

What Happens When You Donโ€™t Treat Heartworm?

Heartworm is a roundworm parasite that is transmitted to dogs through mosquitos. Preventative medicine, like IverhartAdvantage Multi, or Tri-Heart Plus, is the best way to keep your pet protected from heartworm, but if your dog contracts this disease, consultation with your vet is essential.

Most dogs with heartworm can undergo some form of treatment, but they should be evaluated for heart, liver, and kidney function first to assess certain risks. Some dogs with heartworm can fight the disease off without treatment, but the risk of death or serious damage to your petโ€™s health is high.

Risks Associated With Untreated Heartworm Include:

  • Breathing issues: Heartworms take residence in pulmonary arteries, and at advanced stages, in the lungs. These parasites wreak havoc as they migrate through the organs, causing inflammatory changes and damaging tissue. Coughing is a symptom of heartworm that has affected the lungs, and your pet may have shortness of breath and cough both during exercise and while sedentary.
  • Inactivity: Dogs who were once healthy and active will show less endurance with a continued infection of heartworm. A sign of heartworm is listlessness and pets who appear tired, and these symptoms will endure if the disease goes untreated. Minor activity can cause shortness of breath and coughing, and as the disease worsens, most dogs will avoid exercise.
  • Lack of oxygen: As heartworms begin to grow, they will crowd the dogโ€™s heart chambers. This slows down blood flow and decreases the oxygen supply to the dogโ€™s body. Dogs may experience loss of consciousness due to poor blood flow to the brain, and lack of oxygen will contribute to inactivity.
  • Organ damage: The heart, lungs, kidneys, and liver are at risk of major damage from untreated heartworm disease. Heartworms can live up to seven years in vital organs and indirectly affect other organs like the kidneys from related stress. Their presence can cause permanent and irreversible damage to these organs, other tissues, arteries, and blood vessels.
  • Death: Heartworm can cause sudden death, and some dogs die from heartworm without showing symptoms. The disease typically progresses over several years, and can eventually lead to death due to heart failure, blood clots, bleeding in the lungs, and caval syndrome.

If your pet shows signs of canine heartworm disease, be sure to consult your veterinarian to choose the best course of action.

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Heartworm Disease in Dogs: 5 Things You Should Know
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How to Prevent Heartworm in Dogs

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis, or treatment by your veterinarian. Always seek the advice of your veterinarian or other qualified professionals with any questions you may have regarding a medical condition. Never disregard or delay seeking professional advice due to what you may have read on our website.

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