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Diagnosis of brucellosis
Last reviewed: 23.04.2024
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Diagnosis of brucellosis uses the following survey standards: general blood analysis, urine (in dynamics twice), feces for eggs of worms, biochemical blood test (bilirubin concentration, ALT activity, ACT), blood on Brucellae spp., blood test for Wright, Haddleson reaction, RPGA with brucellosis erythrocyte diagnosticum, Coombs reaction (in dynamics twice), Burne test, ECG, ultrasound of internal organs, roentgenography of the spine, joints, consultation of ophthalmologist, neurologist (according to indications).
Diagnosis of brucellosis should take into account epidemiological prerequisites. In many areas of the middle belt in animals, brucellosis has long since been eradicated - hence, there are no conditions for human infection. 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 brucella (home-made cheese, milk, etc.).
Laboratory confirmation of brucellosis is limited, since brucellae are dangerous pathogens. Their isolation can be carried out only in special laboratories equipped in accordance with the requirements of prevention. In serological and allergological studies, it should be borne in mind that in the vaccinated against brucellosis (vaccinated at risk, professionally in contact with animals), the results of serological reactions, and especially allergic tests, may be positive for a long time.
Of the serological reactions, the most informative RA (Wright's reaction) is the most informative. Agglutination on glass (Heddleson's reaction) is not used for diagnosis.
It is proposed to identify individuals who are subject to a survey for brucellosis, for mass surveys for epidemiological indications. Haddleson's reaction often gives false positive results. To a certain extent, this is due to cross-reactions with a number of antigens (Yersinia, a causative agent of tularemia, anti-cholera vaccination, etc.). It should be borne in mind that B. Melitensis and B. Abortus have cross-reactions between themselves, but not with B. Canis, so a special diagnosticum is needed to detect antibodies to this brucella, which is not yet released. Perhaps this is one of the reasons that this type of brucellosis is rarely detected.
In the case of an acute septic form of brucellosis, antibodies can be determined at week 2 of the disease, and their titer subsequently increases. The allergic test becomes positive at the end of the first and the second week. When chronic forms of growth titer antibodies are often not detected. It should be borne in mind that setting an allergic test (Burne test) can provoke the appearance of antibodies or the buildup of their titer. Other serological reactions: RPHA, acute phase reactions - are less informative than Wright's 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 to exclude brucellosis (except HIV-infected, in which all HRT reactions disappear).
[Differential diagnosis of brucellosis
Significantly different depending on the form of brucellosis. Differential diagnosis of acute-cut brucellosis should be performed with many diseases, which are accompanied by high fever. The main difference between brucellosis is satisfactory state of health of patients at a temperature of 39-40 C, although in some diseases (lymphogranulomatosis, tuberculosis), well-being can also remain satisfactory at high temperature. For these diseases are characterized by organ damage: a significant increase in any group of lymph nodes, changes in the lungs.
In the acute form of brucellosis, there are no focal organ lesions (metastases), there are only enlarged liver and spleen, there are no changes in blood.
Differential diagnosis of brucellosis is rather complicated, especially if it is carried out with chronic forms of the disease. Their peculiarity is the defeat of joints, in connection with which they should be differentiated from many diseases characterized by arthritis.
Acute arthritis can occur with many acute infectious diseases (pseudotuberculosis, yersiniosis, mumps, rubella, scarlet fever, etc.). In such cases, the diagnosis facilitates the presence of symptoms, characteristic of a particular infectious disease.
A more severe purulent lesion of the joints is observed in sepsis and generalized forms of a number of diseases ( sap, melioidosis, listeriosis). The difference between these diseases is a serious condition of patients, whereas patients with brucellosis feel themselves satisfactory. Monoarthritis of large joints are the result of gonorrhea or chlamydia (in combination with urethritis and other manifestations of these diseases).
Brucellosis is the only infectious disease in which chronic polyarthritis develops, so it must be differentiated from polyarthritis of another etiology: rheumatoid arthritis, systemic lupus erythematosus of 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 conducted to exclude these diseases.