A DANGEROUS UPTICK FOR DOGS

More canines are testing positive for a lesser-known tick-borne disease. It could be an early warning sign for humans.

- LILA SEIDMAN

WESTERN blacklegged ticks are migrating to Southern California from the northern part of the state.

Dog owners may need to be on alert for a disease many have never heard of — anaplasmosis, spread by the same tick that transmits Lyme disease.

Anaplasmosis can make dogs feverish or lethargic, turn their nose up at food and lose weight, but many show no sign of illness at all. In rare circumstances, though, dogs can bleed from the nose, have neck pain and suffer seizures.

The percentage of dogs across California that tested positive for exposure to the bacterium that causes anaplasmosis skyrocketed in the last five years, nearly tripling between 2021 and 2024, according to data from the nonprofit Companion Animal Parasite Council.

Humans can get the disease too. Dogs get more tick bites and are tested more often for vector-borne diseases than people, so they can be sentinels for their owners.

"It’s a canary in the coal mine," said Brad Ryan, a professional services veterinarian at Antech Diagnostics, a company that offers testing and other services to vets. "When the prevalence starts to go up in the animal population, we know that the public health risk has, by default, also gone up.”

Anaplasmosis and Lyme disease are spread by western blacklegged ticks.

More than half of California counties are labeled as high infection risk, including Santa Barbara and San Diego. The rise began after several years of decline.

In Los Angeles County, which is deemed moderate risk, about 1.2% of dogs are now testing positive — more than double the 0.5% five years ago.

The Companion Animal Parasite Council believes its numbers are an undercount, estimating they are capturing only 30% of the parasite activity in a given geographic region.

'It's very much here'