Ehrlichiosis is a tick-borne disease of dogs that is caused by an organism called Ehrlichia. There are several species of Ehrlichia, but the one that most commonly affects dogs and causes the most severe clinical signs is Ehrlichia canis. The brown dog tick, or Rhipicephalus sanguineous, that passes the Ehrlichia to the dog is prevalent throughout most of the United States, but most cases tend to occur in the Southwest and Gulf Coast regions where there is a high concentration of the tick.
There are three stages of the Ehrlichia canis infection: acute, subclinical, and chronic. Approximately one to three weeks following the infection, clinical signs of the acute phase begin and typically last for two to four weeks. The subclinical phase, which does not produce outward clinical signs, lasts for up to five years. If the dog's immune system is unable to eliminate the organism during this stage, the chronic phase will occur and may last for years, depending on the severity of the infection. Dogs that are severely affected can die from this disease.
Although people can get ehrlichiosis, dogs do not transmit the bacteria to humans; rather, ticks pass on the Ehrlichia organism. Clinical signs of human ehrlichiosis include fever, headache, eye pain, and gastrointestinal upset.
