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Ehrlichia spp .: Ehrlichia ewingii (granulocytic ehrlichiosis), Ehrlichia phagocytophila (granulocytic ehrlichiosis) and Ehrlichia chaffeensis (monocytic ehrlichiosis) - Microscopic exam; Molecular diagnosis (PCR)

 

Information (24/04/14)

 

The Ehrlichia are obligate intracellular bacteria transmitted by ticks that have been associated for decades with animal disease of veterinary importance. However, since the late 1980s they began to describe cases of human infections.

Species of bacteria that were considered included in the genus Ehrlichia, and some after phylogenetic studies are no longer considered Ehrlichia are listed below:

Ehrlichia ewingii is a Gram - negative bacterium circular Ehrlichia genus, family Anaplasmataceae with a wide geographical distribution, although the Central, South and Southeast US are geographical regions with greater presence. Ehrlichia ewingii primarily affects dogs, but can also infect people. Ehrlichia ewingii cause canine granulocytic ehrlichiosis and human granulocytic ehrlichiosis (also called human granulocytic anaplasmosis -AGH-).

The life cycle of this microorganism involves intermediate host where mature, arthropod vectors usually infected ticks (Amblyomma americanum specifically and Rhipicephalus sanguineus), which transmit the infection during feeding. Direct transmission from a common host to an unusual host is considered rare, but can be transmitted through the use of needles or surgical material vaccinations. The organism colonizes the membrane surrounding the cytoplasmic vacuoles infected mammalian host eukaryotic leukocytes. Inside the vacuoles cytoplasmic, and divided resides within them, forming intracellular pools (morulae).

In infected animals Ehrlichia ewingii, associated clinical signs appear between 7 and 14 days after infection and include fever, lethargy, difficulty walking, polyarthropathy and neurological manifestations such as ataxia, paresis, proprioceptive deficits and vestibular dysfunction.

In people, ewingii Ehrlichia infection causes fever, chills, headache, myalgia, arthralgia, nausea, accompanied by leucopenia, thrombocytopenia and slight elevation of transaminases. In addition, there may be diarrhea, petechial rash, maculopapular rash and malaise. Those immunosuppressed individuals, such as people infected with HIV / AIDS are at increased risk of contracting the disease.

In Europe they described clinical and laboratory confirmed this human disease in Slovenia, the Netherlands and Sweden cases.

Among rodents, white-footed mouse (mouse white belly), besides being a host for the larvae of Ixodes scapularis, would be the main reservoir of the granulocytic Ehrlichia. Among other small rodents they have been found infected Tamias striatus (Squirrel Eastern US), Clethrionomys gapperi (South vole US), Blarina brevicauda and Sorex cinereus (insectivorous shrews). Found infected in Europe also small rodents.

Among the larger mammals, Odocoileus virginianus (white tailed deer) is involved as a reservoir in US Europe has found the infection in Capreolus capreolus (roebuck) both in UK and Switzerland, and Rupicapra rupicapra (chamois) in Switzerland.

Recommended tests for diagnosis:

 

The diagnosis is based on microscopic identification of clusters of intracellular bacteria (morulae) within the cytoplasm of neutrophils can be observed in blood smears; in detecting antibodies (ELISA) or by detecting its DNA molecular diagnostic methods (PCR).

Serologic tests, and take time to have developed antibodies to identify the genus Ehrlichia to cause infection but not the species, so the molecular diagnosis as the most sensitive method for identification of Ehrlichia is recommended ewingii .

Tests in IVAMI:

 

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