Ehrlichiosis ewingii infection is an infectious disease

Infectious disease

Infectious diseases, also known as communicable diseases, contagious diseases or transmissible diseases comprise clinically evident illness resulting from the infection, presence and growth of pathogenic biological agents in an individual host organism...

 caused by an intracellular bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, Ehrlichia ewingii

Ehrlichia ewingii

Ehrlichia ewingii is a species of rickettsiales bacteria.Previously known to infect dogs, it has recently been associated with human infection .There is currently no serological test.PCR can be used in diagnosis....

. The infection is transmitted to humans by Amblyomma americanum

Amblyomma americanum

Amblyomma americanum, or lone star tick, is a species of tick in the genus Amblyomma. It's average length is 1/4 inch.-Distribution:...

. This tick can also transmit Ehrlichia chaffeensis

Ehrlichia chaffeensis

Ehrlichia chaffeensis is a species of rickettsiales bacteria.It is named for Fort Chaffee.It is the causative agent of human monocytic ehrlichiosis....

, the bacteria that causes Human monocytic ehrlichiosis

Human monocytic ehrlichiosis

Human monocytotropic ehrlichiosis is a form of ehrlichiosis associated with Ehrlichia chaffeensis.This bacteria is an obligate intracellular pathogen affecting monocytes and macrophages.-Ecology & Epidemiology:...

 (HME).

Mechanism of Illness

Humans contract the disease after a bite by an infected tick of the species Amblyomma americanum

Amblyomma americanum

Amblyomma americanum, or lone star tick, is a species of tick in the genus Amblyomma. It's average length is 1/4 inch.-Distribution:...

.

Those with an underlying immunodeficiency (such as HIV

HIV

Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

) appear to be at greater risk of contracting the disease. Compared to HME, ewingii ehrlichiosis has a decreased incidence of complications.

Like Anaplasma phagocytophilum

Anaplasma phagocytophilum

Anaplasma phagocytophilum is a gram-negative bacterium that is unusual in its tropism to neutrophils...

, the causative agent of human granulocytic ehrlichiosis, Ehrlichia ewingii infects neutrophils. Infection with E. ewingii may delay neutrophil apoptosis

Apoptosis

Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...

.

Symptoms

Patients can present with fever, headache, myalgias, and malaise. Laboratory tests may reveal thrombocytopenia, leukopenia, and evidence of liver damage.

Diagnosis

In endemic areas, a high index of suspicion is warranted, especially with a known exposure to ticks. The diagnosis can be confirmed by using PCR. A peripheral blood smear can also be examined for intracytoplasmic inclusions called morulae.

See also

• Human monocytic ehrlichiosis
  Human monocytic ehrlichiosis
  Human monocytotropic ehrlichiosis is a form of ehrlichiosis associated with Ehrlichia chaffeensis.This bacteria is an obligate intracellular pathogen affecting monocytes and macrophages.-Ecology & Epidemiology:...
  
  
• Human granulocytic ehrlichiosis
• Ehrlichiosis (canine)