Human monocytic ehrlichiosis is an infectious disease transmitted by ticks. The main symptoms are myalgia, rashes, fever. Nausea, abdominal pain, signs of damage to the respiratory and urinary, as well as the central nervous system are less common: photophobia, vomiting at the peak of cephalgia, impaired consciousness, rigidity of the occipital muscles, paresis, paralysis. Diagnosis consists in the detection of pathogens by microscopy of blood smears, using PCR. Treatment is carried out by etiotropic, pathogenetic, symptomatic means.
A28.8 Other specified bacterial zoonoses not classified elsewhere
Monocytic human ehrlichiosis is a transmissible disease. Nosology was first described by hematologist Maeda in 1986 (USA), ehrlichia in 1935. The disease is common in Russia, Spain, Mali, Portugal, Italy, Belgium, USA, Denmark, Norway. The seasonality of the disease is associated with the activity of vectors (late spring – early winter), with peaks in May-June and October-December. Children and men predominate among the sick, mainly residents of rural areas. The age of infected patients is more often 40-50 years.
The causative agent of infection is the intracellular bacterium Ehrlichia, species E. muris, E. chaffeensis. Reservoirs and sources of human monocytic ehrlichiosis in the wild are deer, less often horses, dogs, goats, hamsters, coyotes, mice. Carriers are ticks, most often A. americanum, D. variabilis, I. pacificus, I. persulcatus. It is believed that up to 50% of the Ixode mite population is affected by ehrlichia. During suction, bacteria enter the human bloodstream with saliva.
Main risk factors:
- immune deficits of any etiology
- age over 50
- living in areas with high humidity, mixed forests
- low income level, in which people are forced to live in unfavorable social and hygienic conditions, work in tick habitats. Poverty can be an indirect factor of immunodeficiency, a decrease in the level of literacy, awareness of tick-borne diseases, and methods of their prevention.
When the tick is sucked, the pathogen, along with saliva, enters the thickness of the skin. Lymphogenically, ehrlichia enter the bloodstream, reproduction occurs inside endotheliocytes and monocytes. After penetration into the leukocyte cell, the rapid binary division of the bacterium begins, an initial body is formed, which then turns into a cluster of elementary bodies inside the cell (morula).
After the destruction of the cell, microorganisms enter the bloodstream, where they can infect other cells, more often leukocytes. Ehrlichia affects various organs (skin, liver, central nervous system, bone marrow), where infectious granulomas are detected. The possibility of long-term persistence of bacteria inside the cells of the human body and the chronic course of human monocytic ehrlichiosis is not excluded.
The incubation period is about 14 days, less often 1-30 days. The disease begins acutely, with pronounced general intoxication symptoms: weakness, fatigue, decreased performance, headaches. The condition is accompanied by fever over 38 ° C, chills, the duration of the pyrexia period can be up to one and a half weeks. 2/3 of patients with ehrlichiosis have a sore throat, dry cough, nasal congestion.
Other symptoms of infection are an increase in submandibular lymph nodes, muscle and joint pain, redness of the conjunctiva of the eyes, throat. Less often there are episodes of increased blood pressure, spotted tubercle rashes on the skin of the thighs, shins and body, which pass without peeling and do not require treatment. 10% of patients develop symptoms of meningoencephalitis: photophobia, hallucinations, difficulty in contact, vomiting at the height of headache, decreased strength in the extremities.
The most severe complications of pathology are symptoms of respiratory (respiratory distress syndrome of adults) and renal insufficiency, myocarditis, hypotension, coagulopathy, hemorrhagic manifestations. Toxic shock is registered in 2-5% of patients. Neurological symptoms occur in 20% of cases of human monocytic ehrlichiosis, including a change in mental status, ataxia, severe headache, weakness, convulsions.
Confirmation of the diagnosis and treatment is carried out by an infectious disease specialist. Sometimes a neurologist’s consultation is required, other specialists are involved according to indications. During the survey, the doctor carefully collects an epidemiological history: the fact and duration of tick suction, the presence of chemoprophylaxis. The main clinical, laboratory and instrumental symptoms of human monocytic ehrlichiosis are:
- Physical data. An objective examination may reveal maculopapular rash on the trunk, hips and shins, facial hyperemia, conjunctiva, regional enlargement of lymph nodes, redness of the throat, moderate hepatomegaly, rarely splenomegaly. During auscultation of the lungs, single dry wheezes are detected, the heart – relative bradycardia, muffling of heart tones. There is an increase in blood pressure. Meningeal symptoms are necessarily checked.
- Laboratory tests. In the general blood test – leukopenia, lymphopenia, monocytopenia, thrombocytopenia, acceleration of ESR, less often anemia. The activity of ALT, AST, alkaline phosphatase, LDH increases many times during biochemical screening. In the general clinical analysis of urine, proteinuria, erythrocyturia can be diagnosed. The liquorogram is characterized by lymphocytic pleocytosis, an increase in the amount of protein.
- Identification of infectious agents. Microscopy of a thin stained smear of blood or cerebrospinal fluid in the cytoplasm of neutrophils and monocytes reveals morules (vacuoles) containing clusters of ehrlichia. The PCR method is used before prescribing antibiotics. Serological studies (ELISA, RNIF, immunoblotting) are diagnostically significant from the second week of the disease. An expensive and time-consuming method is to isolate the causative agent of ehrlichiosis in the cell culture of histiocytoma of dogs.
- Instrumental methods. Chest radiography visualizes pulmonary infiltrates in 50% of patients. When neurological symptoms appear, a CT scan of the brain is prescribed. Ultrasound of the abdominal cavity, kidneys and lymph nodes can reveal hepatosplenomegaly and regional lymphadenopathy, exclude inflammatory urological symptoms. On an ECG, a third of patients show conduction disturbances, diffuse changes in the myocardium of the left ventricle.
Differential diagnosis is carried out with pyroplasmosis characterized by anemia and splenomegaly, granulocytic anaplasmosis of a person, the clinical manifestations of which are practically indistinguishable from monocytic ehrlichiosis (laboratory verification is necessary). Ixodic tick-borne borreliosis occurs with the presence of erythema, signs of damage to the motor system, heart and central nervous system; sennetsu fever causes pathology of the lymph nodes, spleen.
Outpatient treatment is allowed for mild and moderate nosology. Hospitalization is recommended for children, pregnant and elderly patients. It is believed that inpatient stay is necessary in 50-70% of cases. About 7% of patients are hospitalized in intensive care units. The fact of vector suction should be alarming in relation to mixed infections with other vector-borne tick-borne diseases.
Bed rest is recommended for up to 3-5 days of stable normal body temperature. Treatment of patients with myocarditis is carried out in a strictly horizontal position. Due to the damage to the liver tissue, a sparing diet is prescribed: marinades, fatty, fried, confectionery, seasonings, coffee, alcohol are excluded. The drinking regime should be increased due to boiled water and oral detoxification solutions.
Standards of medical care for patients with symptoms of ehrlichiosis have not been developed. It is recommended to start treatment no later than the 5th day of the disease and continue for at least 7-10 days, despite the fact that the improvement of the patient’s well-being occurs after 24-48 hours from the start of the drug correction. Therapy of human monocytic ehrlichiosis is usually carried out with the following drugs:
- Etiotropic. The most effective means are tetracycline antibiotics (doxycycline, tetracycline), alternatives are rifampicin and chloramphenicol. The use of sulfonamides, according to some studies, can lead to myocarditis, therefore it is not recommended. Ehrlichia are insensitive to antibacterial drugs of the penicillin, cephalosporin series.
- Pathogenetic. Detoxification is carried out by intravenous infusions of glucose-salt, succinate-containing solutions, chlosol, antipyretics (except aspirin), painkillers are used. With neurological manifestations, glucocorticosteroids, anticonvulsants, diuretics are prescribed. For myocarditis, NSAIDs, potassium preparations, ATP, inosine, antihistamines are indicated.
- Symptomatic. They include medications that relieve symptoms that occur during the disease or treatment: vitamins, local anti-inflammatory drugs for irrigation of the oral and nasopharyngeal mucosa, antitussive, antidiarrheal, antispasmodics, sorbents, enzymes, psychotropic, antihypertensive, antiarrhythmogenic pharmaceuticals. Ventilator, oxygen therapy can be used.
A special approach is required for patients suffering from monocytic ehrlichiosis against the background of immune deficiency, especially HIV infection. The described isolated cases account for the share of deaths, most often the cause of death is hemorrhagic manifestations, pancytopenia, acute renal and multiple organ failure. It is important that patients receive etiotropic drugs (doxycycline) in adequate dosages in a timely manner.
The combined use of doxycycline and the essential oil of A. conyzoides revealed the potentiating effect of the latter on the activity of the antibiotic. The presence of essential oils also hinders the repair mechanism necessary for the cell division of microorganisms, since these oils act on bacterial membranes, contributing to their rupture. The antioxidant and antiprotozoal activity of the plant has been confirmed.
Macrophage activation syndrome is a dysfunctional hyperactive and potentially fatal response of the immune system that leads to multi–organ failure; the trigger of the condition is often monocytic ehrlichiosis. Positive dynamics in this syndrome was revealed during the treatment of patients with an experimental combination of glucocorticosteroids, doxycycline and anakinra.
Prognosis and prevention
The prognosis with timely detection and treatment is more often favorable, the mortality rate is 3-5%. The duration of the persistence of symptoms reaches several weeks, sometimes months. The significance of human monocytic ehrlichiosis for modern clinical infectology lies in the potential increase in the number of deaths from a generalized form of the disease among a growing number of HIV-positive patients.
There is no specific prevention (vaccination). Non-specific measures are the wearing of overalls and closed shoes when visiting forest-steppe zones, the use of anti-tick repellents, the correct removal of the vector when detected, preventive administration of a course of etiotropic antibiotics.