Sections View Full Chapter Figures Tables Videos Full Chapter Figures Tables Videos Supplementary Content + Print Section ++ For further information, see CMDT Part 32-13: Other Rickettsial & Rickettsial-Like Diseases + Key Features Print Section ++ ++ Essentials of Diagnosis ++ Infection of monocyte or granulocyte by tick-borne gram-negative bacteria Nine-day incubation period; clinical disease ranges from asymptomatic to life-threatening Malaise, nausea, fever, and headaches ++ General Considerations ++ Human ehrlichiosis and anaplasmosis are endemic in the United States Ehrlichiosis typically occurs in men aged 60–69 years; anaplasmosis typically occurs in men over 40 years old Ehrlichia chaffeensis Most common species infecting humans Seen primarily in Arkansas, Missouri, Oklahoma and New York Ehrlichia ewingii Causes human granulocytic ehrlichiosis similar to anaplasmosis Constitutes almost 10% of ehrlichiosis cases Most cases in the United States are reported from the Midwest and Southeast Ehrlichia muris eauclairiensis is seen in the upper Midwestern United States Anaplasma phagocytophilum Causes human granulocytic anaplasmosis Most cases in the United States are reported from New England, New York, Minnesota, and Wisconsin Increasingly being reported from Asia, South Korea, Mongolia, China (where a new species [Anaplasma capra] has been identified), and Northern Europe CDC reports that the incidences of human monocytic ehrlichiosis, granulocytic ehrlichiosis and, in particular, anaplasmosis are increasing; coinfection may occur + Clinical Findings Print Section ++ ++ Human monocytic ehrlichiosis Clinical disease ranges from mild to life-threatening Incubation period: 1–2 weeks Prodrome then develops, consisting of malaise, rigors, and nausea, high fever and headache A pleomorphic rash may occur Presentation in immunosuppressed patients and older patients tends to be more severe Human granulocytic ehrlichiosis and anaplasmosis Clinical manifestations are similar to those seen with human monocytic ehrlichiosis However, rash is infrequent If a rash is present, coinfection with other tick-borne diseases or an alternative diagnosis should be suspected Persistent fever and malaise are reported to occur for 2 or more years Coinfection with anaplasmosis and Lyme disease or babesiosis may occur, but the clinical manifestations (including fever and cytopenias) are more severe with anaplasmosis than with Lyme disease ++ Differential Diagnosis ++ Infection with Borrelia miyamotoi may mimic anaplasmosis in its clinical manifestations + Diagnosis Print Section ++ ++ Leukopenia, absolute lymphopenia, thrombocytopenia, and transaminitis common Thrombocytopenia occurs more often than leukopenia in human granulocytic ehrlichiosis Examination of peripheral blood with Giemsa stain may reveal characteristic intraleukocytic vacuoles (morulae) in up to 20% of patients Polymerase chain reaction assay is most sensitive in the first week of illness and can be used as a confirmatory test Indirect fluorescent antibody assay available from the CDC and requires acute and convalescent sera + Treatment Print Section ++ ++ Treatment for all forms of ehrlichiosis is with doxycycline, 100 mg twice daily (orally or intravenously) for 10–14 days or until 3 days of defervescence Rifampin is an alternative in pregnant women + Outcome Print Section ++ ++ Complications ++ Rare serious sequelae of human monocytic ehrlichiosis include Acute respiratory failure and acute respiratory distress syndrome Neurologic complications, the most common being meningoencephalitis and aseptic meningitis Acute kidney disease (which may mimic thrombotic thrombocytopenic purpura) Hemophagocytic syndrome Multiorgan failure Reported complications of anaplasmosis include Leukopenia Thrombocytopenia Cerebral infarction ++ Prevention ++ Tick control ++ Prognosis ++ The case fatality rate is 1% with E chaffeensis infections and 0.3% among cases of human anaplasmosis No deaths have been reported from either E ewingii or E eauclairiensis + References Print Section ++ + +Allerdice MEJ et al. A real-time PCR assay for detection of the Ehrlichia muris-like agent, a newly recognized pathogen of humans in the upper Midwestern United States. Ticks Tick Borne Dis. 2016 Feb;7(1):146–9. [PubMed: 26507653] + +Centers for Disease Control and Prevention (CDC). Ehrlichiosis: epidemiology and statistics. Last reviewed 2019 Feb 11. https://www.cdc.gov/ehrlichiosis/stats/index.html+ +Centers for Disease Control and Prevention (CDC). Anaplasmosis: epidemiology and statistics. Last reviewed 2019 Feb 19.+ +Dahlgren FS et al. Undetermined human ehrlichiosis and anaplasmosis in the United States, 2008–2012: a catch-all for passive surveillance. Am J Trop Med Hyg. 2016 Feb;94(2): 299–301. [PubMed: 26621564]