Ehrlichia

Obligately intracellular Gram-negative bacteria

Target Cells: myeloid cells, hepatocytes, endothelial cells

Ehrlichia reside in a phagosome within infected cells in two forms Reticulate and Dense core forms: EM picture

Ehrlichia lack LPS and peptidoglycan

Ehrlichia hijack host cell cholesterol to enter and replicate within target cells.

Ehrlichia exploit autophagy protein to obtain nutrients for their survival and replication.

Have type 1 and type IV secretion systems and & several secreted tandem repeat proteins

Ismail N, Bloch KC, McBride JW. Human
ehrlichiosis and anaplasmosis. Clin Lab
Med. 2010 Mar;30(1):261-92.
doi: 10.1016/j.cll.2009.10.004.

Human Monocytic Ehrlichiosis:

For more information about Ehrlichiosis, pls visit the CDC weblink below.
https://www.cdc.gov/ehrlichiosis/index.html

Life Cycle:

Life Cycle of Amblyomma americanum that transmit the agent of human monocytic ehrlichiosis

Ismail N, Bloch KC, McBride JW. Human ehrlichiosis and anaplasmosis. Clin Lab Med. 2010 Mar;30(1):261-92. doi: 10.1016/j.cll.2009.10.004.

Challenges in Ehrlichiosis

Challenges in Diagnosis

Nonspecific clinical manifestation

Lack of gold standard laboratory test limitations of serology, PCR, culture

Challenges in Treatment

Resistance to commonly used antibiotics for Gram negative bacteria

Late Doxycycline treatment is ineffective

Challenges in Prevention

Vaccine is not available.

Pathogenesis of Ehrlichiosis

Model of inflammasome activation via canonical and non-canonical pathways

Ismail N, Sharma A, Soong L, Walker DH. Review: Protective Immunity and Immunopathology of Ehrlichiosis. Zoonoses (Burlingt). 2022 Jan 6;2(1):10.15212/zoonoses-2022-0009. doi: 10.15212/zoonoses-2022-0009