The Truth About Heartworm Disease in Cats and Dogs

Heartworm disease is a very serious disease in both cats and dogs, but the unique physiology of each species means that it is really two very different diseases. As you learn about the similarities and differences here, however, remember the bottom line: both dogs and cats need heartworm testing and year-round heartworm prevention.

Heartworm in Dogs

Prevalence and risk:
Heartworm disease is a year-round health  threat that has been diagnosed in all 50 states

Transmission:
Dogs become infected through the bite of mosquitoes, which acquire heartworm larvae from infected dogs, coyotes, foxes and wolves.

Heartworm  characteristics:
Heartworms in dogs grow to an average of 12 inches in length. Worms live 5-7 years.

Host animal:
Dogs are a natural heartworm host; heartworms that live inside a dog mature, mate and produce offspring.

Susceptibility:
Nearly 100% of dogs exposed to infective heartworm larvae become infected.

Worm numbers:
The average number of heartworms in an infected dog is 14-20. It is not uncommon for a dog to have more than 50 worms.

Disease  characteristics:
Worms living in the heart, lungs and arteries cause an inflammatory response that results in blockages in blood vessels. The damage from heartworms can be permanent, affecting a dog’s health and quality of life. Heartworm disease tends to progress as worm numbers grow and cause damage to arteries and organs.

Disease symptoms:
Symptoms in dogs usually start with a cough, which worsens as the disease  progresses. Fatigue, difficulty breathing and weight loss are common in later stages. Ultimately, affected dogs can experience heart failure and death.

Diagnostic testing:
Heartworm is easily diagnosed in most dogs with a simple blood test. Testing is  recommended before the dog is started on preventive, then annually thereafter.

Treatment:
An FDA-approved medication is available to eliminate heartworms in dogs.

Prevention:
An estimated 37% of dogs in the U.S. are  on heartworm prevention.

The American Heartworm Society recommends year-round heartworm  prevention. Prevention is easy and highly effective!

Heartworm in Cats

Prevalence and risk:
Heartworm disease is a year-round health  threat that has been diagnosed in all 50 states

Transmission:
Cats become infected through the bite of mosquitoes, which acquire heartworm larvae from infected dogs, coyotes, foxes and wolves.

Heartworm  characteristics:
Heartworms in cats are shorter than those in dogs, averaging 8-9 inches in length. Worms live 2-4 years.

Host animal:
Cats are a susceptible heartworm host, but are more resistant than the dog. Most worms do not survive to be mature adults, but still cause damage.

Susceptibility:
Approximately 75% of cats exposed to infective heartworm larvae become infected.

Worm numbers:
Most cats with infections have less than 6 heartworms; 1- to 2-worm infections are  common.

Disease  characteristics:
Cats are highly sensitive to heartworms  and, unlike dogs, do not need to harbor adult worms to become ill. Heartworm larvae can trigger a severe immune reaction called heartworm associated respiratory disease (HARD); this syndrome occurs in an estimated 50% of heartworm infections in cats.

Disease symptoms:
Cats develop an asthma-like lung disease with respiratory distress and chronic coughing or vomiting. In cats with adult  worms, the death of just one worm can cause sudden death.

Diagnostic testing:
Heartworm in cats is difficult to diagnose with blood tests. Further testing, including  x-rays, may be required to make a diagnosis. Blood tests are recommended  before a cat is started on a preventive.

Treatment:
There is no approved treatment for heartworms in cats.

Prevention:
Less than 5% of cats in the U.S. are on heartworm prevention.

The American Heartworm Society recommends year-round heartworm  prevention. Prevention is easy and highly effective!