General characteristics and taxonomy
Members of the family Anaplasmataceae are typical causative agents of anthropozoonoses. From a taxonomic perspective, they belong to the class Alphaproteobacteria and the order Rickettsiales.
The life cycle of these microorganisms is inextricably linked to host cells, as they are obligate intracellular parasites. In the body of mammals (humans, horses, cows, sheep, deer), the bacteria purposefully infect circulating blood cells, predominantly various pools of leukocytes, as well as cells of the hematopoietic system. In addition to mammals, the host range may include fish and insects.
Modern pathogen classification
For many years, the classification of these microorganisms was revised. In 2001, based on accumulated clinical, epidemiological, molecular, and genetic data, the family Anaplasmataceae was definitively established as an independent taxon.
Pathogenic representatives for humans belong to three genera: Ehrlichia, Anaplasma, and Neorickettsia. They cause diseases that differ in their target cells:
- Causative agent of human granulocytic ehrlichiosis (anaplasmosis): Anaplasma phagocytophilum. It parasitizes inside neutrophils.
- Causative agents of monocytic ehrlichiosis: Ehrlichia chaffeensis and Ehrlichia muris. They predominantly infect monocytes.
- Causative agent of Sennetsu fever: Neorickettsia sennetsu. The infection is endemic to Japan.
History of the discovery of ehrlichioses
The generic name Ehrlichia was proposed in 1945 by the Soviet scientist Sh.D. Moshковский. The bacteria were named in honor of the prominent immunologist Paul Ehrlich, highlighting their specific tropism for hematopoietic cells.
For a long time, these microorganisms were considered exclusively a veterinary problem, but in the late 20th century the situation changed:
- Human monocytic ehrlichiosis. The first clinical case was described in 1986 in the USA by researcher K. Maeda. Subsequently, the presence of the disease was confirmed in European countries and several African states.
- Granulocytic ehrlichiosis (anaplasmosis). It was discovered in 1994 by a group of scientists led by D. Bakken. The researchers detected the pathogen directly inside neutrophils. The clinical presentation of the first described case was accompanied by severe fever closely resembling monocytic ehrlichiosis. In Europe, the first case of anaplasmosis was registered slightly later, in 1997, in Slovenia.
Briefly: answers to topical questions
What are the morphological features and tinctorial properties of bacteria of the family Anaplasmataceae?
Bacteria of the family Anaplasmataceae are Gram-negative obligate intracellular parasites. They are located in the cytoplasm of infected cells (within phagosomes), where they form compact groups resembling mulberries—morulae. A single vacuole can contain from 3 to 50 pathogens. Romanowsky-Giemsa staining is used for microscopy of blood smears to identify specific clusters of bacteria inside monocytes or neutrophils.
Which arthropods are specific vectors of human anaplasmosis and ehrlichioses?
Ixodid ticks serve as specific vectors for the causative agents of human anaplasmosis and ehrlichioses. Different species of ixodid ticks act as vectors for monocytic ehrlichiosis and granulocytic anaplasmosis.
What laboratory diagnostic methods are used to confirm ehrlichiosis and anaplasmosis?
Serological, molecular-genetic, and microscopic methods are used for the laboratory confirmation of ehrlichiosis and anaplasmosis.
- Serological methods—examination of paired sera using immunofluorescence assays (IFA, indirect IFA) or enzyme-linked immunosorbent assay (ELISA) with a specific antigen.
- Molecular-genetic methods—detection of pathogen DNA in the blood using polymerase chain reaction (PCR).
- Microscopy—examination of blood smears stained with Romanowsky-Giemsa to search for specific intracellular bacterial clusters (morulae).
Which changes in the complete blood count are most characteristic of granulocytic anaplasmosis?
The most characteristic complete blood count changes in human granulocytic anaplasmosis are a decrease in platelet and leukocyte counts, as well as a shift in the leukocyte formula. Typical laboratory findings include:
- thrombocytopenia;
- leukopenia;
- band neutrophil predominance;
- lymphopenia;
- monocytopenia;
- increased erythrocyte sedimentation rate (ESR).
Which antibacterial drugs are the drugs of choice for etiotropic treatment of infections caused by Anaplasmataceae?
The drugs of choice for the etiotropic treatment of ehrlichioses and anaplasmoses are tetracyclines, primarily doxycycline. Chloramphenicol is a reserve drug, used less frequently or in cases of intolerance or unavailability of tetracyclines.
Human-pathogenic genera can be easily remembered using the mnemonic "Ehrlich Analyzes Neatly": Ehrlichia, Anaplasma, Neorickettsia.
Class and exam questions
In which specific cells does Anaplasma phagocytophilum parasitize?
This pathogen parasitizes inside neutrophils, causing granulocytic ehrlichiosis (anaplasmosis).
Who proposed the genus name Ehrlichia and when?
The name was proposed by Sh.D. Moshkovsky in 1945 in honor of Paul Ehrlich.
Which species cause monocytic ehrlichiosis?
The main causative agents of monocytic ehrlichiosis are Ehrlichia chaffeensis and Ehrlichia muris.
What else to study on this topic
- Clinical presentation and pathogenesis of monocytic ehrlichiosis
- Features of granulocytic anaplasmosis: from infection to symptoms
- Epidemiology of Sennetsu fever in Japan
- Laboratory diagnostic methods for intracellular blood parasites
Study the full topic in the «Microbiology» course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on the topic "Anaplasmataceae family" and 4,383 other subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 141 video lectures on the subject
Other topics in the section "Anaplasmas, Ehrlichiae"
Free video lessons: microbiologyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.