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Brucellosis: symptoms, diagnosis, treatment of brucellosis in humans


Brucellosis is a severe infection caused by specific bacteria of the genus Brucella, the source of which are domestic animals (zoonotic infection) and multiple transmission. To date, cases of brucellosis are recorded worldwide, with a higher incidence in countries with developed animal husbandry.

Causes of Brucellosis

The disease is caused by specific bacteria that belong to a separate genus Brucella, it has 7 species. In humans, 3 types of disease are caused - B. melitetnsis (also often causes disease in goats), B. suis (can develop in the body of pigs) and B. abortus (occurs in cattle). These bacteria are small in size, polymorphic - rod-shaped, spherical (cocci) and convoluted forms. Dispute and capsules do not form. Brucella have a number of features that are called the factors of aggression and contribute to the development of the disease in humans and animals, these include:


  • Synthesis of hyaluronidase is a specific enzyme that breaks down the hyaluronic acid of the extracellular substance, which contributes to the penetration of bacteria into the human body and their distribution in it.
  • Isolation of substances that inhibit (inhibit) the phagocytic activity of macrophage leukocytes - this makes it possible for intracellular parasitism of bacteria inside the cells of the immune system and the long-term infection process in the human body.
  • The ability to allergize the human body due to the release of protein substances, metabolic products of bacterial cells.
  • Isolation of powerful endotoxin in the death and destruction of bacterial cells - it causes a strong intoxication of the human body and a metabolic disorder in it.
  • The formation of specific L- and S-forms of bacteria that are resistant to antibiotics and human immunity, due to a change in their genetic structure.

These features (factors of aggression) of brucella determine the peculiarity of the course of the disease and the mechanism of its development (pathogenesis). The most virulent (ability to cause severe disease) is the type of bacterium - B. melitetnsis. All bacteria that cause brucellosis, are fairly stable in the environment, in food (meat, milk), the skin and hair of animals, they can maintain their viability for a long time (from several months to six months and longer). Boiling in water kills them instantly, they are also sensitive to antiseptic solutions (hydrogen peroxide, alcohol, furatsilin, bleach, chloramine).

Epidemiology of the disease and its transmission

Brucellosis refers to a zoonotic infection. This means that animals are the main reservoir and source of infection. A person becomes infected from domestic farm animals, namely goats, cows and cattle. Brucellosis is an infectious disease with several possible routes of transmission of the pathogen:

  • The alimentary path is the most frequent way of transmission, in which the pathogen enters the human body with contaminated food of animal origin (meat, milk, cheese). Especially if these products are consumed raw or not thermally processed.
  • Contact path - the infection of a person occurs when his skin or mucous membranes contact directly with a sick animal during its care, taking birth at livestock farms or individual farms. Also, such infection is possible during the slaughter of a sick animal, cutting up its carcass, processing the skin and skins of sick animals after their slaughter.
  • Airborne pathway - the pathogen enters the human body with inhaled air. Such a transmission path is realized when breathing air contaminated with dust or microscopic particles of wool and epidermis of sick animals.

Considering the peculiarities of the epidemiology of brucellosis, the source of infection and its modes of transmission, this pathology is characterized by a higher incidence in people working in livestock farms or in individual farms. Usually, the occurrence of cases of brucellosis in humans is preceded by an epizootic (surge in incidence) of this infection in animals. A person, during his illness, is not contagious for surrounding people. Also described several cases of infection with brucellosis in the laboratory, during the cultivation of a culture of bacteria on nutrient media in order to identify and identify the pathogen.

The mechanism of development of brucellosis

Entrance gates (place of introduction of the pathogen into the body), depending on the route of transmission, are mucous membranes of the digestive tract (stomach or intestines), organs of the respiratory system, skin and visible mucous membranes (eyes, oral cavity). In the area of ​​the introduction of bacteria, inflammatory changes do not develop. Bacteria, as an agent alien to the body, are captured by the cells of the immune system (neutrophils and macrophages) and spread throughout the body. Then they settle in the lymphoid tissue and give rise to the development of several pathogenetic phases of the disease, which include:

  • The phase of lymphogenous drift is the entry of Brucella bacteria into the lymphoid tissue (lymphocytes, spleen) with their active reproduction.
  • Primary generalization (toxic-septic phase) - characterized by a mass release of bacteria from the lymphoid tissue into the blood. This phase coincides with the onset of the clinical manifestations of the disease, since the circulation of brucella in the blood leads to severe intoxication and allergization of the body.
  • The dissemination phase - with the flow of blood, the bacteria spread throughout the body and settle in various organs. The favorite places of their localization are the liver, lymph nodes (re-penetration), spleen, red bone marrow. In places and secondary reproduction after dissemination (distribution in the body), foci of necrosis (cell death) and an inflammatory reaction in the form of granulomas develop.

In the future, in the absence of treatment and sufficient adaptive capabilities of the human body and the functional activity of the immune system, partial repression of bacteria multiplication and chronic infection occur. The foci of infection with a good immune response and protective abilities of the body are surrounded by connective tissue and are leaked with calcium salts, which makes it possible to limit the infection process. After a disease, a persistent species-specific immunity is formed to brucellosis - immunity to re-infection.

Symptoms of Brucellosis

Brucellosis has an incubation period (the time period from the moment of infection until the first clinical manifestations of the disease appear) for brucellosis about 1-2 weeks. There are 3 clinical forms of brucellosis, which have their own specific manifestations of the disease - acute, chronic and residual brucellosis.

Symptoms of acute brucellosis

Acute brucellosis is characterized by a pronounced course with manifestations of general intoxication of the body and a process duration of up to 3 months. The main symptoms of this clinical form are:

  • Severe fever with a long course and high figures of body temperature (38-40º C).
  • There is no correlation between the high temperature and the well-being of the sick person — even with very high numbers, the patient may feel relatively good.
  • Fever is prolonged with periods of temperature drop to subfebrile numbers (37.5º C) or to normal values. Then, after a short while, the fever returns - a wave-like fever.
  • An enlarged spleen and liver in which active proliferation of brucellosis bacteria occurs is a hepatolienal symptom.
  • The development of severe sweating, which increases in the period of decreasing body temperature.
  • Non-specific symptoms of general intoxication - headache, malaise, weakness, loss of appetite, muscle and joint aches. These manifestations do not depend on body temperature, and can develop even with its normal value.
  • Moderate hypotension (decrease in systemic arterial pressure) on the background of intoxication of the body.

The severity of symptoms of an acute course of brucellosis depends on the reactivity of the human body and the number of bacteria in it.

Symptoms of chronic brucellosis

The chronic course of the disease is characterized by focal lesions of the organs in which bacteria multiply. The main symptoms of this form of brucellosis are:

  • Periodic fever with a temperature of about 38º C, but more often it persists within subfebrile numbers (37.5º C).
  • Generalized lymphadenopathy - an increase in all groups of lymph nodes.
  • Symptoms of affection of the autonomic nervous system - excessive sweating, emotional lability (change of mood during a short period of time).
  • Signs of a lesion of the musculoskeletal system are the most common symptom of chronic brucellosis, which is characterized by unilateral inflammation of large joints (arthritis) - hip, knee, elbow and shoulder joint.
  • Infectious myocarditis is an inflammation of the heart muscle, manifested by periodic pain in the heart, not associated with physical exertion.
  • Prolonged enlargement of the liver and spleen (hepatosplenomegaly).

In the case of severe dissemination of bacteria, various focal symptoms may develop - an inflammatory process in the eyes, organs of the urogenital sphere, muscles and skin in the form of painful dense formations.

Symptoms of residual brucellosis

Symptoms of internal organs, heart, blood vessels and large joints are developing, even after the body is freed from the bacteria brucellosis. These changes are persistent and may persist throughout the subsequent life of the person who has had it. Residual brucellosis is a kind of complication of the infection.


For the specific diagnosis of brucellosis, laboratory test methods are used, which include:

  • Bacteriological study with isolation of bacterial culture of the pathogen and their identification.
  • Serological diagnosis is the most common method of diagnosis, in which using a variety of techniques (agglutination reaction, enzyme immunoassay), an increase in antibody titer to certain types of brucella is detected.

For additional diagnostics, in order to determine the severity and localization of structural changes in organs, a clinical analysis of blood and urine, X-ray and ultrasound methods of instrumental examination are used. The basis for the final diagnosis is the identification and isolation of the pathogen or antibodies to it.

Brucellosis Treatment

The complex of therapeutic measures in the case of brucellosis is performed only in a medical hospital and includes:

  • Etiotropic therapy - aimed at the destruction of the pathogen with the help of antibacterial agents. To do this, antibiotics of the tetracycline group and rifampicin are used for a long time, for at least 6 weeks, to completely destroy the pathogen and prevent the formation of resistant forms of bacteria and the development of chronic brucellosis.
  • Pathogenetic therapy - necessary to reduce the severity of damage to internal organs during the development of bacteria in them, including detoxification (intravenous drip of saline solutions and special sorbents), antiallergic treatment with antihistamines, vitamins, immune system stimulants, painkillers (analgesics) and sedatives .

After the treatment, the discharge from the hospital is carried out no earlier than 2 weeks after the normalization of body temperature and the absence of laboratory clinical signs of the disease. After that, sanatorium treatment is recommended.

Prevention of brucellosis

Prevention is aimed at preventing the person from infecting with brucella or in creating immunity to the ingress of bacteria into the body (immunity). For this purpose, 2 types of events are used:

  • Nonspecific prophylaxis - identification and isolation of sick animals at livestock enterprises, bacteriological control of food of animal origin, provision of personnel with personal protective equipment (respirators or masks, gloves, gowns) are carried out.
  • Specific prophylaxis is aimed at creating immunity in people living in areas that are unfavorable for brucellosis and livestock workers. This is carried out using vaccines containing live, attenuated bacteria of 3 main types of Brucella.

The incidence of brucellosis today remains at a fairly high level. Constant cases of Brucella infection are recorded worldwide. More often this occurs in countries with developed animal husbandry. Given the severity of the pathology with frequent transition to the chronic form, the main focus in the fight against infection is its prevention.

| 21 June 2015 | | 514 | Infectious diseases
Leave your feedback

Blue Mermaid: Thank you, it was very helpfull. I also recommand watching (Sex kills) episode season2 from Dr House to help fix some of the clinical manifestation of the Dx :)

Анна Ананичук: This is great and very informative - however it is very difficult to follow a presentation that is not synced to the audio :(

H.B.C. Reloaded: Yes it’s possible for raw milk to become contaminated but it’s also possible for anything else to become contaminated what about all the E. coli outbreak‘s from spinach and kale? Should we not prohibit the sale of raw vegetables and base it on the same logic?

Sarah Basham: I thought I had lymphoma for about a month before my doctor called me and told me I had this. I was scared out of my mind.

Betty Gillis: Great presentation. Just one issue though, Bartonella is not self limiting, and will not resolve on it's own. If you have chronic bartonella or what they call stationary bartonella, it can reside in your body for a very long time, and at some point you run the risk of it developing into cancers, heart disease, MS...a myriad of ailments. Unfortunately a round of ABX will not clear you of the disease.