Ehrlichioses are infectious diseases that are transmitted to humans by ticks. The Ehrlichia can lead to severe acute or chronic infections with fever, chills, headache, muscle and joint pain, liver and kidney dysfunction.
Ehrlichia are spherical bacteria. Four of the Ehrlichia species known to date can be transmitted to humans via ticks.
Ehrlichioses are among the newly emerged infectious diseases (Emerging Infectious Diseases) that have so far been diagnosed rather rarely. The first known serious case in humans occurred in 1986 in the United States. Until then, Ehrlichiosis was only known in animals, such as dogs. In the case of a high fever of unknown cause, Ehrlichiosis should be considered during the tick season.
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Incubation period and symptoms of Ehrlichiosis
After being infected with Ehrlichia, it usually takes 12 days for the first symptoms to appear. The symptoms are usually unspecific at first and can be flu-like, but very pronounced. Some of those affected can also suffer from pneumonia with a dry cough. Rashes may occur in children.
Overview of possible symptoms:
In addition to the symptomatic course, there is also an asymptomatic course, i.e. the infection with Ehrlichia runs unnoticed in over half of all cases. Ehrlichiosis can lead to many complications and, in the worst case, even be fatal.
Transmission of Ehrlichiosis
In terms of the path of infection, Ehrlichiosis is to be regarded as a zoonosis that originates in various wild animals and humans are infected by ticks, which act as vectors. Ehrlichiosis can cause serious symptoms in humans.
Human Granulocytic Ehrlichiosis (HGE) is caused by a special kind of Ehrlichia. The spherical Ehrlichia belong to the rickettsial family of bacteria. Ehrlichia are transmitted to humans by tick bites.
Once the Ehrlichia get into the host’s bloodstream, they attack a certain form of white blood cells (granulocytes) that play an important role in the immune system. Unlike other types of bacteria, they are not enclosed by the granulocytes and rendered harmless with the help of enzymes (phagocytosis). The Ehrlichia are able to escape the defense mechanism of the granulocytes by penetrating them and multiplying in them. In this way, the Ehrlichia prevent the infected granulocytes from rendering other bacteria harmless and thus no longer being able to exercise their defense function.
A tick can also transmit several pathogens with one bite, so that double infections (in addition to Ehrlichiosis, for example, also or) can be transmitted.
Groups at Risk for Infection
The risk group for Ehrlichiosis includes people who spend a lot of time in the forest for professional reasons, for example forest workers and foresters. But there is also a risk of transmission during leisure activities in forests and meadows.
The severity of the disease in the end depends primarily on the age of the person and the state of their immune system.
Medical diagnosis of Ehrlichiosis
In the blood count, HGE is typically shown by an increased number of leukocytes (white blood cells) and a decreased number of thrombocytes (blood platelets). In addition, the liver values can be increased.
To confirm the diagnosis, the pathogen is determined by determining antibodies in the blood serum and by the polymerase chain reaction (PCR). A short piece of the genetic material (DNA) of the pathogen is reproduced using PCR. The subsequent examination of the molecular building blocks that make up this piece of DNA can then prove whether or not it is actually the bacterium you are looking for.
Since the symptoms are unspecific, some similar diseases such as borreliosis, babesiosis or typhoid must be ruled out. Therefore, if symptoms such as fatigue, fever, muscle pain and headache and a previous tick bite occur, blood tests are initiated to look for various pathogens.
If the results of the physical examination and the laboratory values give a reasonable suspicion that those affected are suffering from Ehrlichiosis, then therapy should be started before the examinations to confirm the diagnosis are completed.
Treating Ehrlichiosis with antibiotics
In some cases, the immune system can overcome Ehrlichiosis without treatment. Usually, the Ehrlichia infestation is so strong that the immune system does not manage to destroy the pathogen itself, but an antibiotic has to be used. Suitable antibiotics are doxycycline (from the group of tetracyclines) or rifampicin.
A single tick can also be the carrier of several pathogens at the same time. For example, if a tick is infected with both Ehrlichia and Borrelia burgdorferi, the causative agent of Lyme disease, the risk of a double infection increases the later the tick is discovered after the infestation. In this case it is possible that the much more serious Lyme disease is masked by symptoms of Ehrlichiosis. Therefore, the administration of antibiotics over a four-week period can be useful to cure both diseases.
How does Ehrlichiosis work?
As a rule, the symptoms of Ehrlichiosis subside within 24 to 48 hours of starting antibiotic treatment. After this time, a rapid decrease in fever can usually be observed. However, it can take weeks for the Ehrlichiosis to completely heal.
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Depending on how strong the Ehrlichia infestation, how weak the immune system of the person affected is and how old it is, the susceptibility to other diseases can increase. As a result, Ehrlichiosis takes a serious course and can be fatal.
Prevent ticks and thus an Ehrlichiosis
Since Ehrlichiosis is caused by bacteria, vaccination is not possible. The best prevention is protection against tick bites. Long trousers and long-sleeved shirts should be worn during the tick season, especially in wooded areas and tall grass. Light-colored clothing is recommended because it reduces the risk of ticks and makes it easy to spot and remove the small, still running animals.
In addition, repellants against ticks that should be applied to bare skin and clothing also help. These lose their effect after a while and should therefore be reapplied regularly.
If a tick has bitten itself, it should be carefully removed as quickly as possible in order to prevent the transmission of Ehrlichia. This is because these require a suction time of around 24 hours for effective transfer.