Infectious Disease Compendium

Ehrlichia

Microbiology

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

Diagnosis is serology. If lucky will see morulae in the WBC.

Epidemiologic Risks

E. canis: tick bite.

E. chaffeensis: tick bite in south central and southeastern United States. Missouri, Tennessee, and Oklahoma have the most cases.

Wisconsin Ehrlichia: ticks. Probably underdiagnosed (PubMed).

E. ewingii: platelet transfusion (PubMed).

E. muris: tick bite. Eastern Europe and Japan; a close relative of E. muris in Minnesota and Wisconsin. Also in Ixodes cookei ticks int the Northeastern United States (PubMed).

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

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). Now in Hudson Valley and Long Island. That would be New York.

Syndromes

Incubation time is 2 weeks or so.

They all cause fevers, chills, headache red eyes, and myalgias. A rash rash that usually spares the face, but may spread to the palms and soles. One the organisms that I call a doxycycline deficiency state.

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.

Treatment

Doxycycline or tetracycline. Quinolones may work but haven't been tested. Rifampin for the tetracycline allergic.

Notes

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

Last update: 06/02/18