Ehrlichiosis Overview


The Ehrlichiosis of man is still relatively unknown infectious disease which is transmitted by ticks. Possible pathogens are the gram-negative bacteria of the genus Ehrlichia, which otherwise mainly cause Ehrlichiosis in dogs and horses. In most cases the disease is mild or even symptom-free, but in some cases it can also lead to serious complications.

What is Ehrlichiosis?

According to dictionaryforall, the first case of Ehrlichiosis caused by a tick bite in humans was described in 1986 in the United States. Before that, honesty was only known in dogs or horses. The pathogen was discovered by the German doctor Paul Ehrlich (1894 to 1915). Although the pathogen was known early on, an infection with Ehrlichia was first observed in a dog in Algeria in 1935.

During the Vietnam War, many American soldiers’ dogs developed Ehrlichiosis. The Ehrlichien have therefore long been a term in veterinary medicine. The causative agent for Ehrlichiosis in dogs is called Ehrlichia canis. Ehrlichia chaffeensis and Ehrlichia phagocytophilia are particularly responsible for causing this disease in humans. Ehrlichia chaffeensis is currently only active in North Africa.

It is the cause of human monocytic Ehrlichiosis (HME). In Germany there is only one subspecies of the pathogen Ehrlichia phagocytophilia, which causes human granulocytic Ehrlichiosis (HGE). The genus Ehrlichia belongs to the order Rickettsiales. Their representatives are therefore rickettsiae. All Ehrlichia are gram-negative bacteria that can infect the monocytes, granulocytes or macrophages in the blood.


Ehrlichiosis is caused by an Ehrlichia infection transmitted by a tick bite. This applies to both humans and animals. In the case of animals, horses and dogs that have come into contact with ticks are particularly affected. Dogs are mainly infected by the brown dog tick (Rhipicephalus sanguineus). In Germany, the human Ehrlichiosis is mainly dominated by the wooden ram.

The pathogens enter the bloodstream through a tick bite. There they penetrate monocytes, granulocytes or macrophages and often multiply inside the cell without being noticed. Monocytes and granulocytes are part of the blood and belong to the group of leukocytes (white blood cells). The immune system usually fights off the infection very quickly. In the case of immunocompromised or elderly people, however, there are also severe forms that can even lead to death in individual cases.

Symptoms, ailments & signs

In about half of Ehrlichia infections, the disease is symptom-free. If symptoms do occur, they become noticeable about two weeks after the tick bite. This can lead to nausea, vomiting, abdominal pain, diarrhea, high fever and headache. Reddening of the skin also often occurs.

Symptoms can be mild or in some cases severe. The immune competence of the organism is decisive for the course of the disease. In severe cases, respiratory problems, heart muscle inflammation, or muscle fiber breakdown are also observed. Even rarer complications can manifest in meninges and encephalitis.

Ehrlichiosis can also be fatal, especially in elderly and immunocompromised people. Overall, the clinical picture is very diverse and unspecific. The small number of cases observed has not yet fully verified which symptoms can also occur in humans. In Germany, the first case of confirmed Ehrlichiosis was not described until the early 1990s.

Furthermore, Ehrlichiosis does not always occur in isolation. Sometimes it is associated with Lyme borreliosis in the form of a so-called double infection, since several different pathogens can be transmitted via the tick. Similar symptoms also occur in dogs or horses. This has already been confirmed by long-term observations.


The unequivocal diagnosis of Ehrlichiosis requires a multitude of differential diagnoses from other possible diseases. On the one hand, this is due to the fact that the symptoms are often very unspecific. On the other hand, other pathogens are also transmitted through a tick bite.

In addition to a large number of pathogens, autoimmune diseases or leukemia must also be ruled out. For the diagnosis, however, it is important to know that a tick bite has occurred. If there is an initial suspicion of ehrlichiosis, only genetic evidence of the pathogen or the detection of antibodies against Ehrlichia can clearly confirm the diagnosis.


In Ehrlichiosis there are only very rare cases of serious complications. As a rule, the course of the disease is harmless and only leads to mild discomfort. Ehrlichiosis initially leads to headaches, vomiting and severe nausea. These symptoms can also be accompanied by diarrhea and a high fever.

In some cases, there is airway problems or inflammation of the heart muscles. In the worst case, it can also lead to encephalitis, which can be fatal. However, these cases are very rare. Ehrlichiosis often occurs together with Lyme disease.

Treatment is based on symptoms and usually does not lead to complications. If the symptoms are weak, no treatment is necessary; the Ehrlichiosis disappears on its own and does not lead to any further complaints. Treatment with antibiotics is advisable if symptoms become more severe.

This also leads to a positive course of the disease. It usually takes two days for the ehrlichiosis to subside. Areas with ticks should be avoided to prevent Ehrlichiosis or Lyme disease. Tick ​​vaccinations can also be considered preventively.

When should you go to the doctor?

A doctor should always be consulted after a tick bite. If specific signs of Ehrlichiosis are noticed, medical evaluation and treatment is essential. Typically, one to four weeks after the tick bite, there is a high fever, severe headache, muscle and joint pain, and general malaise.

These symptoms must be clarified by a doctor immediately. Medical advice is required at the latest when abdominal pain and diarrhea or signs of pneumonia are noticed. If left untreated, Ehrlichiosis can cause serious complications such as heart failure, kidney failure, and circulatory collapse.

The risk of complications is particularly high in the elderly and in patients with immunodeficiency or a serious underlying disease. Anyone who belongs to these risk groups should go to the family doctor immediately if they suspect Ehrlichiosis. If the complications mentioned occur, the following applies: Call an emergency doctor immediately or go to the nearest hospital. In severe cases, first aid measures must be provided. In addition, after the initial treatment, further visits to the family doctor are indicated, because only he can ensure that the disease has completely healed.

Treatment & Therapy

Since Ehrlichiosis is often symptom-free, therapy is not always necessary. In many cases it even goes completely unnoticed and heals on its own. This also applies to most of the symptomatic Ehrlichiosis. However, if the fever is high, antibiotics such as doxycycline or tetracycline are given.

The body reacts to this therapy with a rapid drop in fever within 24 to 48 hours. Complete healing occurs after several weeks. Treatment with doxycycline also works if Ehrlichiosis occurs together with Lyme disease. The borreliosis pathogen is also combated by this active ingredient.

Outlook & forecast

The prognosis for Ehrlichiosis in humans is usually good. As a rule, the disease is very mild or often without symptoms. After healing, there is usually no secondary damage. Treatment is therefore often not necessary. However, severe disease courses are also observed, which are noticeable, among other things, by fever, chills, muscle pain, joint pain, headache and nausea. After treatment with quinolones, rifampicin or tetracyclines, the symptoms subside within 14 days.

Even with more severe courses, there is usually no long-term damage to be feared. However, life-threatening complications can occur in people with a weakened immune system. These complications include pneumonia, sepsis, or impairment of the central nervous system.

In these cases, rapid emergency medical assistance is required to overcome the life-threatening condition. If the CNS is involved, consequential damage in the form of neurological and psychiatric diseases can occur. However, lethal courses of Ehrlichiosis are extremely rare.

However, if the complications are successfully treated, a complete cure can also be expected in most cases. Since Ehrlichiosis is transmitted by ticks, it can also occur in the form of a double infection together with Lyme disease. In doing so, it often hides the borreliosis as part of standard therapy. However, if broad spectrum antibiotics are used, both diseases can be treated successfully in the early stages of Lyme disease.


Since very few cases of Ehrlichiosis have occurred in Germany so far, there is also little experience with its prevention. The pathogen is not spread everywhere. Basically, however, tall grass or forest edges should be avoided during the tick season. Long-legged, long-sleeved and light-colored clothing is preferable. Dark clothing would make it more difficult to find any ticks that might roam freely. The risk of infection is greatly reduced by the early mechanical removal of the tick from the host, for example with a tick tweezer.


Follow-up care for Ehrlichiosis proves to be relatively difficult. The disease is still largely unexplored so that direct and rapid treatment is not possible in most cases. If the disease is not immediately examined and treated by a doctor, in the worst case scenario it can lead to serious complications and even death.

For this reason, Ehrlichiosis must first and foremost be recognized early so that a doctor should be consulted at the first symptoms. In most cases, Ehrlichiosis is treated with medication, usually with antibiotics to reduce the symptoms. It is important to ensure the correct dosage with regular intake so that the symptoms can be completely alleviated.

The antibiotics sometimes have to be taken for several weeks, even if the symptoms have completely disappeared before that. With timely treatment, there are no further complications or complaints and the life expectancy of the person affected does not decrease. No further measures are necessary after the therapy, so that there is no need for follow-up care.

You can do that yourself

Ehrlichiosis in humans is, unlike in dogs or horses, a rare disease. In many cases, the infection goes unnoticed by those affected, but if symptoms appear, a patient should consult a doctor promptly. The best self-help measures are to avoid tick bites, strengthen the immune system, and see a doctor immediately if you become ill.

Ehrlichiosis is mainly transmitted in Central Europe by a certain type of tick, the wood tick. These insects live mainly in tall grass and on low bushes and shrubs. In order to prevent a bite and thus a possible infection with the pathogens of Ehrlichiosis or other dangerous diseases such as Lyme disease or early summer meningoencephalitis (TBE), certain preventive measures must be taken.

Long pants and long-sleeved tops should always be worn when hiking. After being outdoors, the body should be searched for ticks and these should be removed promptly. Anyone who has pets should also check them for ticks. At least in high-risk areas, it is advisable to use additional chemical insect repellants when walking or hiking through the forest or over meadows with tall grass.

A healthy immune system can help ensure that an infection does not lead to the onset of the disease, or at least that it is brief and mild. The immune system is best promoted by a healthy lifestyle that includes adequate sleep, a vitamin-rich, predominantly plant-based diet and regular exercise, preferably in the fresh air. A high-fat, meat-heavy diet, little to no physical activity, and excessive consumption of alcohol and cigarettes weaken the immune system and should be avoided.