History
Clinical manifestations of ehrlichiosis usually begin 5-14 days after the tick bite. Approximately 68% of patients with human monocytic ehrlichiosis (HME) report a tick bite, and 83% of patients have a history of tick exposure in the 4-week period before onset of symptoms. Onset is abrupt or subacute.
The histories for HME, human granulocytic anaplasmosis (HGA), and E ewingii infection are similar and may include the following [1, 2] :
-
Tick bites or exposure (>90%)
-
Fevers (>90%)
-
Headaches (>85%)
-
Malaise (>70%)
-
Myalgias (>70%)
-
Rigors (60%)
-
Nausea (40%)
-
Vomiting (40%)
-
Anorexia (40%)
-
Confusion (20%)
Skin rash is not considered a common feature of ehrlichiosis and should not be used to rule in or rule out an infection. E chaffeensis infection can cause rash in up to 60% of children, but rash is reported in fewer than 30% of adults. Rash is not commonly reported in patients infected with E ewingii or the E muris-like organism. [13]
Physical Examination
Physical findings due to ehrlichiosis are minimal.
Splenomegaly is not uncommon, but some patients develop hepatomegaly. Lymphadenopathy is very uncommon.
Complications
Complications of ehrlichiosis include the following:
-
Renal failure
-
Respiratory failure
-
Coagulopathy
-
Myocarditis
-
Encephalopathy
-
Coma
-
Seizures
-
Septic shock
-
Female Lone Star tick, Amblyomma americanum, found in the southeastern and Midatlantic United States. It is a vector of several zoonotic diseases, including human monocytic ehrlichiosis and Rocky Mountain spotted fever. Courtesy of the CDC/Michael L. Levin, PhD.
-
Map of the United States showing the distribution of the Lone Star Tick, which is the principle vector for ehrlichiosis.
-
Established and reported distribution of anaplasmosis vectors Ixodes scapularis and Ixodes pacificus, by county, in the United States from 1907-1996. Courtesy of the Division of Vector-Borne Infectious Diseases at the Centers for Disease Control and Prevention.
-
Anaplasmosis incidence by age. Courtesy of the Centers for Disease Control and Prevention.
-
Ehrlichiosis incidence by age. Courtesy of the Centers for Disease Control and Prevention.
-
This graph displays the number of human cases of ehrlichiosis caused by Ehrlichia chaffeensis reported to the Centers for Disease Control and Prevention (CDC) annually from 2000 through 2016. *From 2000 to 2008, ehrlichiosis was included in the reporting category “human monocytic ehrlichiosis” in reports to the National Notifiable Diseases Surveillance System (NNDSS). **Since 2008, ehrlichiosis has been reported to the NNDSS under the categories “Ehrlichia chaffeensis infections,” “Ehrlichia ewingii infections,” and “Undetermined ehrlichiosis/anaplasmosis infections”, which include infections caused by Ehrlichia muris eauclairensis. Only E chaffeensis infections are shown above. Courtesy of the CDC (https://www.cdc.gov/ehrlichiosis/stats/index.html).
-
This graph shows the number of ehrlichiosis cases caused by Ehrlichia chaffeensis reported from 2000 through 2016 by month of onset to illustrate the seasonal trends. Cases are reported in each month of the year, although most are reported in June and July. Courtesy of the CDC (https://www.cdc.gov/ehrlichiosis/stats/index.html).
-
This graph shows the number of US ehrlichiosis cases caused by Ehrlichia chaffeensis and reported to the CDC from 2000 to 2018. Courtesy of the CDC (https://www.cdc.gov/ehrlichiosis/stats/).
Tables
|
Human monocytic ehrlichiosis (HME) |
Human granulocytic anaplasmosis (HGA) |
Cell type Affected |
Monocytes |
Granulocytes |
Organism |
E chaffeensis |
A phagocytophilum |
Vector |
Amblyomma americanum (Lone Star tick) |
Ixodes scapularis (black-legged tick), Ixodes pacificus (Western black-legged tick) in California, Ixodes ricinus in Europe, and probably Ixodes persulcatus in parts of Asia |
Location |
Southeastern and south-central United States |
Wisconsin and Minnesota, less active in New York and Connecticut, also California |
Rash |
30% of adults, 60% of children |
Rare |
Prognosis |
~3% mortality |
< 1% mortality |
