One patient was asymptomatic. However, there has been a preliminary report of a human fatality possibly associated with E. canis infection. Ehrlichia, members of the family Rickettsiaceae, are obligate, intracellular bacteria that parasitize mononuclear or polymorphonuclear leukocytes. Canine ehrlichiosis, also known as tropical canine pancytopenia, is caused by E. canis and has an acute and chronic phase. The chronic phase of the disease, which is often fatal, is characterized by pancytopenia and bone marrow hypoplasia.
Preliminary data suggest that human ehrlichiosis, like canine ehrlichiosis, is tickborne.
Infection with E. sennetsu results in an acute febrile illness with lymphocytosis and postauricular and posterior cervical lymphadenopathy similar to mononucleosis. Currently, the diagnosis of human ehrlichiosis is based on an IFA test that shows a fourfold or greater increase or decrease in antibody titer against E. canis with a minimum titer of 80. However, insufficient data exist to recommend chloramphenicol as an alternative antibiotic. Physicians should consider the possibility of ehrlichiosis when patients have a febrile illness and a history of recent tick exposure. Specimens should be submitted to CDC through state health departments.