Ehrlichia (ehrlichia)

The family Anaplasmataceae includes 4 genera - Anaplasma, Ehrlichia, Neorickethsia, Wolbachia. The generic name Ehrlichia (erlichia) is proposed in honor of the German microbiologist Ehrlich.

The closest connections are noted with the genera Rickettsia and Orietiria. Representatives of the family Anaplasmataceae are obligate intracellular proteobacteria, multiplying in specialized vacuoles of eukaryotic cells and having common genetic, biological and ecological characteristics. In human pathology, Anaplasma, the causative agent of granulocyte human anaplasmosis (HAP) and Ehrlichia chajjfeensis, is the causative agent of monocytic human erchychosis (MEC), the smaller is Neorickertsia sennetsu and B. Ewingii.

[1], [2], [3]

Morphology of Ehrlichia and Anaplasm

Ehrlichia and anaplasm are gram-negative, coccobacillary bacteria of small size (length from 0.5 to 1.5 mmkm). Morphologically, pleomorphic coccoid or ovoid form microorganisms that acquire a dark blue or purple color when painted according to Romanovsky. They are detected in specialized vacuoles - phagosomes in the cytoplasm of infected eukaryotic cells in the form of compact accumulations - morul, named so because of the external similarity to mulberry berries.

Two different morphological forms of erlichia are distinguished (similar to chlamydiae): larger size of reticular cells characterizing the stage of vegetative development, erlichia of cells of smaller size characterizing the stationary stage of rest.

Microecology of the pathogen, host range and natural habitat

Ehrlichia and apaplasm are obligate intracellular parasites that infect mammalian mesoderm cells, primarily blood cells and vascular endothelium. Their reservoir are various types of warm-blooded animals. Carriers of the pathogens are ixodid mites, which, when fed with blood, transmit microorganisms to their hosts. According to the spectrum of human cells to be affected, there are distinguishable pathogens of monocytic human erlichiosis (mainly affecting monocytes of peripheral blood) and granulocyte anaplasmosis of man (mainly granulocytes, mainly neutrophils).

Antigenic structure of erlichia and anaplasm

The representatives of the family Anapfosmataceae have common antigenic determinants, which determine the greatest cross reactivity within the genogroups.

[4], [5], [6], [7], [8], [9], [10]

Physiology of Ehrlichia and Anaplasm

Anaplasm and zllicia are slowly growing microorganisms, multiply by transverse binary division, with the presence of vegetative (reticular) and resting (elementary) cells, similarly chlamydial. Representatives of the genera Anaplasma, Ehrlichia, Neorickettsia and Wolbachia are obligate intracellular proteobacteria that multiply in specialized vacuoles (phagosomes or endosomes) of eukaryotic cells designated as morulae. The causative agent of monocytic human erhychosis multiplies in monocytes and macrophages, the causative agent of human granulocyte anaplasmosis in granulocytes (neutrophils).

Factors of Ehrlich pathogenicity and anaplasm

The representatives of the family identified surface proteins that function as adhesins. They interact with lectin-containing associated (for the causative agent of granulocyte human anaplasmosis) receptors of host cells. The presence of factors preventing phagosomal-lysosomal fusion and providing the possibility of intraphagosomal developmental cycle is proved. Anapfosmataceae has a mechanism for delaying spontaneous apoptosis of neutrophils, which contributes to their multiplication in them.

[11], [12], [13], [14]

Pathogenesis and symptoms of erlichiosis and anaplasmosis

The pathogenesis of human granulocyte anaplasmosis and monocytic human erhychosis in the initial stage is due to the process of introduction of the pathogen through the skin and is realized with the participation of the tick-carrier. Primary affect at the site of implantation is absent. The causative agent spreads lymphogenically and then hematogenously. Infection of sensitive target cells occurs in three stages: penetration into the cell (initiation of phagocytosis), reproduction in cytoplasmic vacuoles (phagosomes), bounded by the membrane, exit from the cell. The infectious process with monocytic human erlichiosis is accompanied by the defeat of macrophages of the spleen, liver, lymph nodes, bone marrow and other organs. With severe lesions, hemorrhagic syndrome develops with hemorrhages of the internal organs, gastrointestinal bleeding, hemorrhagic eruptions on the skin.

Pathogenesis and pathological anatomy of granulocyte anaplasmosis in humans have not been adequately studied.

Symptoms of erlichiosis and anaplasmosis resemble ARVI. The rash is detected in no more than 10% of patients with granulocyte anaplasmosis. In patients with granulocyte anaplasmosis, fever and other clinical manifestations quickly pass with tetracyclines, without antibiotic therapy, the duration of the disease can be up to 2 months.

Microbiological diagnosis of erlichiosis and anaplasmosis

Serological diagnosis of erlichiosis and anaplasmosis is currently the most common approach for confirming the diagnosis of human granulocyte anaplasmosis and monocytic human erhychosis. Methods include RNIF, ELISA, immunoblotting, based on recombinant proteins (ELISA / immunoblotting). These methods are highly sensitive and quite specific, Seroconversion is the best method of confirmation on the 1st (25% of patients) - the 2nd (75%) weeks of the disease.

Microscopically examine the subtle smears of the peripheral role in the presence of clusters of small bacteria (morulae) inside neutrophils. PCR allows to identify the acute phase before the use of antibiotics. It is also possible to use isolation on the culture of HL-60 cells.

Prevention and treatment of erlichiosis and anaplasmosis

To treat erlichiosis and anaplasmosis, doxycycline is 100 mg twice daily for 10-21 days. As with other tick-borne infections, granulocyte anaplasmosis of man and monocytic erlichiosis of a person apply measures of nonspecific prevention and anti-malignant measures.