MM; Id 1281-1284

NAMES OF DISEASE:     Ehrlichiosis
                                                  Sennetsu fever
                                                  Sennetsu rickettsiosis
 

OVERVIEW:

After the Ehrlichia sp. is injected into the blood stream by a tick, it enters into either the monocyte or granulocyte, depending on the species of Ehrlichia. There it replicates and destroys its host cell. The symptoms are identical to those of Rocky Mountain spotted fever with the exception that there is no rash.

ETIOLOGICAL AGENTS:    Ehrlichia ewingi
                                                       Ehrlichia chaffeensis
                                                       Ehrlichia equi
                                                      Ehrlichia phagocytophilia
 

EPIDEMIOLOGY:

The disease is transmitted by the bite of a tick. The reservoir is the domestic dog and perhaps the coyote and wolf.
 

PATHOLOGY:

There is a 12-day incubation period during which time it can be found in the blood, lymph nodes and bone marrow. However, the primary target tissue is the leukocyte. The organism is an obligate intracellular parasite which multiples within the cytoplasm of the host cell. Like the Rickettsia, and in contrast to Coxiella, it does not form a vacuole within the cytoplasm. There are mulberry-shaped intracytoplasmic inclusions within the leukocyte, called murula, that are used for diagnosis. There is a leukopenia and thrombocytopenia. In a few people there is a maculopapular or petechial rash, but this is rare.

MANIFESTATIONS:

The symptomology is similar to that of Rocky Mountain spotted fever without the rash, i.e., there is a high fever, toxicity, and myalgia.

DIAGNOSIS:

Diagnosis is based on the finding of intracytoplasmic inclusions in lymphocytes, monocytes and neutrophils or by detecting antibodies to the Ehrlichia antigens, or by PCR assay for Ehrlichia DNA. Elevated serum aminotransfearse is also a clue used in diagnosis.

TREATMENT:

Doxycycline or tetracycline