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Diagnosis of brucellosis
Last reviewed: 03.07.2025
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The following examination standards are used for diagnostics of brucellosis: general blood test, urine test (twice dynamically), stool test for helminth eggs, biochemical blood test (bilirubin concentration, ALT, AST activity), blood test for Brucellae spp., blood test for Wright reaction, Heddleson reaction, RPGA with brucellosis erythrocyte diagnosticum, Coombs reaction (twice dynamically), Burnet test, ECG, ultrasound of internal organs, X-ray of the spine, joints, consultation with an ophthalmologist, neurologist (as indicated).
Brucellosis diagnostics should take into account epidemiological prerequisites. In many areas of the middle zone, brucellosis in animals has long been eliminated - therefore, there are no conditions for infection of people. In these regions, brucellosis is an "imported" infection. It is necessary to clarify the stay in places where brucellosis is still encountered. But sometimes infection occurs through products infected with brucellae (home-made feta cheese, milk, etc.).
Laboratory confirmation of brucellosis is limited, since brucellae are dangerous pathogens. They can only be isolated in special laboratories equipped in accordance with prevention requirements. In serological and allergological studies, it is necessary to take into account that those vaccinated against brucellosis (risk groups that professionally come into contact with animals are vaccinated) may have positive results of both serological reactions and especially allergy tests for quite a long time.
Of the serological reactions, the most informative is the Wright reaction. Agglutination on glass (Heddleson reaction) is not used for diagnostics.
It is proposed to identify individuals subject to examination for brucellosis during mass examinations for epidemiological reasons. The Heddleson reaction often gives false positive results. To a certain extent, this is due to cross-reactions with a number of antigens (yersinia, the causative agent of tularemia, cholera vaccination, etc.). It should be taken into account that B. melitensis and B. abortus have cross-reactions with each other, but not with B. canis, so that a special diagnostic kit is needed to detect antibodies to this brucella, which is not yet available. Perhaps this is one of the reasons why this type of brucellosis is rarely detected.
In the acute septic form of brucellosis, antibodies can be detected in the 2nd week of the disease, and their titer increases thereafter. The allergic test becomes positive at the end of the first and in the 2nd week. In chronic forms, the antibody titer is often not detected. It should be taken into account that the allergic test (Burne test) can provoke the appearance of antibodies or an increase in their titer. Other serological reactions: RPGA, acute phase reactions - are less informative compared to the Wright reaction and are not significant. In recent years, a more sensitive ELISA method has been used to determine IgG and IgM antibodies. Negative results of the Burne test allow us to exclude brucellosis (except for HIV-infected people, in whom all DTH reactions disappear).
[ Differential diagnostics of brucellosis
It varies significantly depending on the form of brucellosis. Differential diagnostics of acute septic brucellosis should be carried out with many diseases that are accompanied by high fever. The main difference of brucellosis is the satisfactory well-being of patients at a temperature of 39-40 C, although with some diseases (lymphogranulomatosis, tuberculosis) the well-being can also remain satisfactory at a high temperature. These diseases are characterized by organ damage: a significant increase in any group of lymph nodes, changes in the lungs.
In the acute septic form of brucellosis, there are no focal organ lesions (metastases), only the liver and spleen are enlarged, and there are no changes in the blood.
Differential diagnostics of brucellosis is quite complicated, especially when it is carried out with chronic forms of the disease. Their peculiarity is joint damage, in connection with which they should be differentiated from many diseases characterized by arthritis.
Acute arthritis may occur with many acute infectious diseases (pseudo tuberculosis, yersiniosis, mumps, rubella, scarlet fever, etc.). In such cases, diagnosis is facilitated by the presence of symptoms characteristic of a particular infectious disease.
More severe purulent joint damage is observed in sepsis and generalized forms of a number of diseases ( glanders, melioidosis, listeriosis). The difference between these diseases is the severe condition of patients, while patients with brucellosis feel satisfactory. Monoarthritis of large joints can be a consequence of gonorrhea or chlamydia (in combination with urethritis and other manifestations of these diseases).
Brucellosis is the only infectious disease that causes chronic polyarthritis, so it must be differentiated from polyarthritis of other etiologies: rheumatoid arthritis, systemic lupus erythematosus, systemic scleroderma, psoriatic arthritis, sarcoidosis. They can be distinguished from brucellosis by a set of clinical signs that are not characteristic of brucellosis. A set of appropriate laboratory and instrumental studies is also carried out to exclude these diseases.