Anaplasma and Ehrlichia species

shu Eyong 

2. Anaplasma phagocytophilium and Ehrlichia species


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Anaplasma phagocytophilum & Ehrlichia species

What type of microbe is it?

Anaplasma phagocytophilium is a small Gram-negative bacterium approximately 0.4–1.3 μm in size. A. phagocytophilum colonizes neutrophils when infecting mammals; however, it may also infect other cells of myeloid and non-myeloid origin. Inside ixodid ticks, it is known to survive in salivary glands and midgut cells. All Ehrlichia sp. are also gram-negative and spherical with a rippled outer membrane that shows no peptidoglycan layer or any lipopolysaccharides.

What disease it causes,

Ehrlichia is a genus of Rickettsiales bacteria that are transmitted to vertebrates by ticks. These bacteria cause the disease ehrlichiosis, which is considered zoonotic because the main reservoirs for the disease are animals. An infection caused by Ehrlichia species is generally referred to as ehrlichiosis. . Anaplasma phagocytophilum causes an acute febrile illness known as anaplasmosis or human granulocytic anaplasmosis (HGA).

How the disease is emerging,

Anaplasma phagocytophilum is an obligate intracellular bacteria that survives and propagates within the host cell and can evade neutrophil antimicrobial functions. A. phagocytophilum infection is acquired through a tick bite and disseminates to the bone marrow and spleen.  A. phagocytophilum can selectively survive and multiply within cytoplasmic vacuoles of polymorphonuclear cells.

It affects the progenitors of myeloid and monocytic lineages, and it is seen in neutrophils in peripheral blood and tissue. The presence of Anaplasma in neutrophils induces proinflammatory responses leading to neutrophil deactivation, and the release of cytokines promotes neutrophil degranulation.

Ehrlichia species are obligately intracellular pathogens and are transported between cells through the host cell filopodia during the initial stages of infection, whereas in the final stages of infection, the pathogen ruptures the host cell membrane. They are also bacteria that can evade the immune system and infect host cells. They preferentially infect white blood cells in the bloodstream, such as neutrophils and macrophages, but have also been found in the spleen, lymph node, and kidney tissue samples.

Signs & Symptoms,

Signs and symptoms of anaplasmosis typically begin within 1–2 weeks after the bite of an infected tick.

Tick bites are usually painless, and many people do not remember being bitten.

See your healthcare provider if you become ill after having been bitten by a tick or having been in the woods or in areas with a high brush where ticks commonly live.

Early signs and symptoms (days 1-5) are usually mild or moderate and may include:

Fever, chills

Severe headache

Muscle aches



Nausea, vomiting, diarrhea, loss of appetite

Signs and symptoms of severe (late-stage) illness can include:

Respiratory failure

Bleeding problems

Organ failure


Risk factors for severe illness:

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