Heartworm Facts
Drs. Foster & Smith Educational Staff

Dog & cats are both affected by heartworm disease
  • The mosquito is the only known vector for transmitting heartworm.

  • The average lifespan of heartworms in untreated pets is 5-7 years in dogs and 2-3 years in cats.

  • Virtually 100% of dogs exposed to infective heartworm larvae become infected; in cats, this number drops to 61% to 90%.

  • Microfilariae are found in the blood of 80%-90% of dogs, while only 20% of cats have these in their blood.

  • Heartworm infection in cats exists everywhere heartworm in dogs exists.

  • The American Heartworm Society (AHS) estimates that only 55% of dogs in the U.S. are currently on a heartworm preventive, leaving 27 million dogs at risk of acquiring heartworm disease.

  • A study performed at North Carolina State University indicated that 25% of cats infected with heartworms were solely indoor cats.

  • Heartworms may infect more than 30 species of animals including coyotes, foxes, wolves and other wild canids, domestic cats and wild felids, ferrets, sea lions, and humans.

  • Prevention is far more effective and less costly than treatment.

  • Research suggests that heartworm disease could be virtually eradicated using available preventives.

  • Heartworms affect cats differently than dogs, but the disease they cause is equally as serious.

Heartworm Frequency Map Courtesy the American Heartworm Society