Ehrlichiosen A28.8 oder A79.8

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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Synonym(s)

Human monocytic ehrlichiosis; Sennetsu fever

History
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Donatia and Lestoquard (description of Ehrlichia canis), 1935; Gordon (description of E. phagocytophila), 1940; Moshkovski, 1945; Tachibana, 1986

Definition
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Mostly tick-borne bacterial infectious disease caused by Ehrlichia species.

Pathogen
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  • Ehrlichia species are obligatory intracellular, Gram-negative bacteria from the Rickettsiaceae family. The different species have developed a specific cell affinity during evolution. Some live exclusively in granulocytes, others only in monocytes. E. platys, a species not yet found in humans, lives in thrombocytes.
  • Honestly, 0.5 µm in diameter are small, obligatory intracellular coccobacilli rods, with sometimes elipsoid and polymorphic appearance.
  • Transmission by ticks: Amblyomma americanum, Dermacentor variabilis, Ixodes scapularis, Ixodes pacificus, Ixodes ricinus, Ixodes dammini.
  • Double or triple infections with Borrelia and Babesia are possible.
  • Ehrlichia sennetsu lives naturally in fish parasites and is often transmitted by eating raw fish.
  • Ehrlichia show tropism for mononuclear cells and multiply densely packed in membrane-enclosed cytosplasmic vacuoles. During further propagation, characteristic morules are formed, which are composed of vacuoles stuck together like mulberries.
  • Ehrlichia infest horses, sheep, goats, cattle, bison, deer, jackals, whitefoot mice, dogs and humans.
  • Exceptions: Anaplasma phagocytophilum (previously Ehrlichia equi and phagocytophila) as the trigger of human granulocytic anaplasmosis. They were formerly counted among the Ehrlichioses. The pathogens live obligatory intracellularly in granulocytes, where they multiply in cytoplasmic vacuoles.

Classification
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A distinction is made between Ehrlichia sennetsu (Sennetsu fever) and Ehrlichia chaffeensis (human monocytic ehrlichiosis).

Occurrence/Epidemiology
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  • E. sennetsu. western Japan and Southeast Asia.
  • E. chaffeensis: USA, South America, Europe, Africa.

Manifestation
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80% are men infected.

Clinical features
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  • In the case of transmission by tick bite there is little itching at the bite site, sometimes the brown-red to black round tick body is still detectable.
  • Sennetsu fever: incubation period 9 days, fever, chills, malaise, headache, insomnia, generalized lymphadenopathy, especially in the neck and throat, possibly spleno- and hepatomegaly. The disease is self-limiting.
  • Human monocyte monocyte ehrlichiosis: fever (in 97% of cases), headache (80%), limb and joint pain (70%), myalgia, anorexia, nausea, vomiting, infectious maculopapular exanthema (approx. 30-40% of cases), possibly pneumonia, cough, diarrhoea, lymphadenopathy (25%), drop in hematocrit, pancytopenia with severe thrombocytopenia (70%), leukocytopenia (60%) in the first 3-7 days, lymphocytosis in the 2nd week, increase in transaminases (86%).
  • Human granulocytic ehrlichiosis (anaplasmosis): 67-75% of all infections are asymptomatic. Incubation period: 5-30 days. Fever (100% of symptomatic cases) and flu-like symptoms with headache, limb, muscle and joint pain, rarely abdominal pain, nausea, vomiting and diarrhea, dry cough and infectious maculo-papular exanthema (2-3% of cases). Leukopenia (50%), thrombopenia (92%), increase in transaminases (91%). Rare pancytopenia.

Laboratory
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  • Decrease of hematocrit, pancytopenia with strong thrombocytopenia, leukocytopenia in the first 3-7 days, lymphocytosis in the 2nd week.
  • Elevated aspartase and ALT levels.

Diagnosis
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  • Microscopy of the blood and bone marrow with detection of morules.
  • QBC: Buffy coat microscopy.
  • Indirect fluorescent antibody detection.
  • PCR with detection of DNA.

Differential diagnosis
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Complication(s)
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  • Acute renal and pulmonary failure.
  • Encephalopathy.
  • Mortality up to 2%.
  • Complicated course, especially in HIV-infected patients.

Therapy
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Tetracycline (e.g. tetracycline-ratiopharm) 4 times/day 500 mg p.o. or doxycycline (e.g. doxycycline AL) 1.5 to 2 mg/kg bw/day or once/day 200 mg p.o. for 14 days are considered sufficient. Alternatively: Rifampicin 10 mg/kg bw/day (maximum 600 mg/day) for 7-10 days. If necessary therapy until the blood count normalizes. Penicillins and cephalosporins (no pharmacological intracellular targets) are generally not effective.

Progression/forecast
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  • Human monocyte monocyte ehrlichiosis: lethality: up to 2%.
  • Human granulocytic monocyte anaplasmosis: lethality: 2-3%.

Prophylaxis
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Tick protection and control.

Tables
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Ehrlichia species with predominantly terrestrial distribution

Vectors

Hosts/infested species

Cell affinity

HGE agent

Ixodes ticks

People

Granulocytes

E. pahgozytophilia

Ixodes ticks

Hoofed animals

Granulocytes

E. equi

Ixodes ticks

Horses, people

Granulocytes

E. chaffeensis

Amblyomma ticks

People, deer

Monocytes

E. canis

Haemaphysialis and Riphicephalus ticks

Dogs

Granulocytes

E. ewingii

Ticks

Rabbit

Granulocytes

E. platys

Ticks

Dogs

Platelets

Ehrlichia species with predominantly aquatic distribution

E. sennetsu

Trematodes in raw fish (peroral route of infection)

People

Monocytes

E. resticii

Cercaria (infestation through peroral route of infection or when bathing in waters contaminated with cercaria)

Horses, dogs

Monocytes

NeoReckettsia helminthocea

helminths in raw fish (peroral route of infection)

Dogs, bears, people

Literature
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  1. Ismail N et al (2017) Tick-Borne Emerging Infections: Ehrlichiosis and Anaplasmosis. Clin Lab Med 37:317-340.

Disclaimer

Please ask your physician for a reliable diagnosis. This website is only meant as a reference.

Authors

Last updated on: 29.10.2020