Heartworm Disease in Dogs and Cats

Parasites can threaten your pet’s wellbeing in multiple ways, with parasites that cause heartworm disease some of the most damaging. These parasites begin their lives as tiny larvae and spread to new hosts through mosquito bites. Eventually, they grow up to a foot long and live in your pet’s heart and blood vessels. Because this parasite is such a threat, the Woodinville Veterinary Hospital & Mobile Services team is sharing everything pet owners should know to protect their pets.

Heartworm transmission and lifecycle in pets

Heartworms differ from other worms, which pets usually pick up from contaminated environments. Heartworms are spread through mosquitoes, who pick up the heartworm larvae when they bite other infected pets or animals. Over about six months, the worms make their way to the pet’s blood vessels near the heart and grow into foot-long adults. In an ideal host, the worms then reproduce and become a new infection source for mosquitoes.

Heartworm disease in dogs

Dogs are the heartworms’ ideal host, with infected dogs carrying anywhere from 30 to more than 100 heartworms. Because the worms can live in a dog for five or more years, the longer they are present, the larger the worm burden becomes. The worms cause inflammation and damage the inside of the heart and lungs, which starts minimally but progresses as more worms are added. 

Most dogs do not show any early disease signs, and the damage is likely irreversible once signs become visible. Heartworm disease signs in dogs may include:

  • Exercise intolerance or fatigue
  • Coughing
  • Weight loss
  • Fluid buildup in the chest or abdomen
  • Death

Heartworm disease in cats

Most pet owners believe that cats are immune to heartworm, but cats are susceptible to infection. However, cats are not ideal hosts, so many heartworms do not survive to adulthood, or the cat’s immune system spontaneously clears the infection. But, some will become infected and since we can’t predict which cats are at greater risk, all cats should be considered at risk for heartworm disease.

Cats typically host only one to three worms, but their immune system response can result in disease signs similar to, or worse, than infected dogs. Signs in cats may include:

  • Coughing, wheezing, or difficulty breathing
  • Weight loss
  • Chronic vomiting
  • Weakness or seizures
  • Sudden collapse or death

Heartworm diagnosis and treatment in dogs

Dogs treated prior to the onset of heartworm infection clinical signs have a greater chance for a full recovery, so our team recommends annual screening for all dogs. We also recommend testing prior to starting a prevention regimen, and six months after a lapse in prevention. A heartworm test for dogs requires only a small blood sample.

Treatment in dogs is available, but can be tough on the dog and expensive for the owner. Treatment usually involves a painful injection series over several months, combined with antibiotics and steroids to reduce the chances of reacting to the dying heartworms and the toxins they release. Infected dogs are also placed on preventive medications that kill circulating immature worms.

Heartworm diagnosis and treatment in cats

Heartworm testing is more difficult in cats than dogs, because they are less likely to harbor adult worms. Multiple blood tests and imaging can be used to detect worms in suspect cats, but routine screening is not recommended in healthy pets. Testing should be performed prior to starting a preventive regimen. 

The medication used to kill adult heartworms in dogs is not safe for cats, which means that infected cats must continue to host the adult worms until they die naturally in two to three years. Medications may help improve heart or lung issues, and cats must be closely monitored for changes. Unfortunately, some cats may die from heartworm infection.

Heartworm prevention for pets

Because you can’t avoid mosquitoes, monthly prevention medications are the only way to keep pets safe from heartworm infection. Preventives are cost-effective and easily administered—usually in topical or flavored chewable form—and must be administered year-round, because any lapse in prevention can leave your pet vulnerable, and because most preventives also control other harmful parasites, including roundworms and hookworms. An annual heartworm preventive supply usually costs around $100 to $150, but treatment can easily cost more than $1,500.

Give your pet the best chance at a healthy life by providing them with year-round, monthly heartworm prevention. Ask our Woodinville Veterinary Hospital & Mobile Services team for more information about heartworm prevention methods, or call us to schedule your pet’s next wellness visit and routine heartworm test.

By |2024-02-15T00:00:12+00:00May 25th, 2023|Uncategorized|0 Comments

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