Moving Ticks Mean Trouble for Dogs

Study finds that tick populations are on the rise and affecting new parts of the U.S.

Tick populations are on the rise and reaching across the United States, concerning many veterinarians about the spread of tick-borne diseases, according to a new study conducted by Idexx Laboratories of Westbrook, Maine.

At least three tick-borne diseases were found in every state: Lyme disease (Borrelia burgdorferi), anaplasmosis (Anaplasma phagocytophilum) and ehrlichiosis (E. canis).

Positive tests for Lyme disease were highest in the Northeast, while positive results for anaplasmosis were highest in the Midwest. In the Southeast, ehrlichiosis has been most widely reported.

Researchers found that the number of Lyme-positive dogs in Connecticut (where 18 percent of the dogs tested positive for Lyme) was from 50- to more than 200-fold greater than those in the southeastern border states of Texas, Louisiana, Mississippi, Alabama, and Florida.

The researchers said they were surprised by the high level of infection detected in the western states of California, Arizona, and New Mexico.

“This is of serious concern to veterinarians,” said Dwight Bowman, Ph.D., Department of Microbiology and Immunology, Cornell University College of Veterinary Medicine. “It tells us ticks are on the move and raising the risk of infection from tick-borne illnesses to regions where they are not only unfamiliar with these diseases and symptoms, but also perhaps unfamiliar with how to prevent illness and protect their pets.”

The researchers said that exposure to urban wildlife and a high incidence of Lyme disease in the northeastern states was expected based on the number of human cases reported. However, dogs testing positive for Lyme disease exposure were also found in the southeastern United States.

“One explanation may be the continual urbanization of America,” said Michael Dryden, DVM, Kansas State University College of Veterinary Medicine.

The rate of ehrlichia-positive dogs was more than twice the national average in the South. Cases of ehrlichiosis due to the E. canis pathogen are considered more common in the southern United States where infestations of the brown dog tick are also more commonly seen.

The report also found cases of heartworm in the South that was detected in more than 3 million dogs in 48 states. Evidence of at least one agent was found in dogs from every state considered.

The Companion Animal Parasite Council, an independent council of veterinarians and other animal health care professionals established to create guidelines to help control internal and external parasites, recommends year-round heartworm, flea, and tick preventives for dogs, for all areas of the country.

For details on tick migration and images of various tick species, visit

Article Categories:
Dogs · Health and Care