Infectious Disease Compendium

Ehrlichia

Microbiology

Intracellular cell wall deficient organisms. Includes E. canis, E. chaffeensis, E. ewingii, E. sennetsu, E. phagocytophilia (now Anaplasma phagocytophilia in humans), close relative of E. muris in Minnisota and Wisconsin .There are a variety of veterinary Ehrlichia as well.

Epidemiologic Risks

E. canis: tick bite.

E. chaffeensis: tick bite in south central and southeastern United States.

Wisconsin Ehrlichia: ticks. Probably underdiagnosed (PubMed).

E. ewingii: platelet transfusion (PubMed).

E. muris: tick bite.

E. sennetsu: eating raw fish in the far East. Yeah. Raw fish.

A. phagocytophilia: tick bites in eastern and western US, also parks in Germany (and probably elsewhere) (PubMed).

The true distribution of these pathogens may be changing as the world warms and the ticks move as a result. E. ewingii has now been found in Indiana and New Jersey (Pubmed). Has it always been there or are the vectors moving? And who would move to New Jersey?

Ehrlichia cases are increasing in the US, whether due to increase awareness, increase in the disease or increasing reporting once people figured where to put the unneeded first 'h' in Ehrlichia (Pubmed).

Syndromes

They all cause fevers, chills, headache and myalgias.

HME more often has a rash. Both have elevated AST and leukopenia.

E. canis: Human monocytic ehrlicheosis.

E. chaffeensis: Human monocytic ehrlicheosis.

Wisconsin Ehrlichia: very similar to E. muris genetically. Fevers and headache.

E. muris: fever, malaise, headache, and lymphopenia, thrombocytopenia and elevated liver-enzyme levels.

E. sennetsu: Human monocytic ehrlicheosis.

A. phagocytophilia: Human granulocytic ehrlicheosis.

Treatment

Doxycycline or tetracycline. Quinolones may work but haven't been tested.

Notes

In HGE 20 - 80% of patients have had Ehrlichia morulae in peripheral blood neutrophils, rare in HME.