Brucellosis (also known as brucellosis, or brucellosis) is a zoonotic disease caused by Brucella infection. Infected animals such as sheep and cattle are the main source of infection for brucellosis. Brucella can be transmitted through broken skin mucous membranes, the digestive tract and the respiratory tract. Acute cases are characterized by fever, malaise, excessive sweating, muscle and joint pain, and enlarged liver, spleen and lymph nodes. Chronic cases are mostly manifested as joint damage, etc.
I. Clinical manifestations and stages
The incubation period is usually 1-3 weeks, with an average of 2 weeks. Some cases have a longer incubation period.
(A) Clinical manifestations
1. Fever: Typical cases show wavy fever, often accompanied by chills, headache and other symptoms, which can be seen in patients of all stages. Some cases may show hypothermia and irregular fever type, and mostly occur in the afternoon or at night.
2. Excessive sweating: Sweating is especially heavy in acute cases and can soak through clothes and bedding.
3.Muscle and joint pain: The pain is generalized muscle and multiple, wandering large joints. Some chronic cases may also have spinal (mainly lumbar) involvement, manifesting as pain, deformity and functional impairment.
4, weakness: almost all cases have this manifestation.
5.Liver, spleen and lymph nodes enlargement: mostly seen in acute cases.
6.Other: male cases may be accompanied by testicular inflammation, female cases may be seen with ovarian inflammation; a few cases may have cardiac, renal and neurological involvement.
(II) Clinical stages
1. Acute stage: with the above clinical manifestations, the duration of the disease is within 6 months.
2. Chronic stage: the disease remains untreated for more than 6 months.
II. Laboratory tests
(A) General laboratory tests
1. Blood picture: white blood cell count is normal or low, lymphocytes are relatively increased, sometimes abnormal lymphocytes may appear, and red blood cells and platelets are reduced in a few cases.
2. Blood sedimentation: The blood sedimentation may be accelerated in the acute stage, but is mostly normal in the chronic stage.
(B) Immunological examination
1, plate agglutination test: Tiger red plate (RBPT) or plate agglutination test (PAT) results are positive, used for primary screening.
2, test tube agglutination test (SAT): titer of 1:l00 ++ and above or titer of 1:50 ++ and above for more than one year of disease duration; or history of Brucella vaccination within six months, titer of 1:100
++ and above.
3, Complement binding test (CFT): titer 1:10 ++ and above.
4.Brucellosis anti-human immunoglobulin test (Coomb’s): titer of 1:400 ++ and above.
(C) Pathogenetic examination
Brucellae were isolated from blood, bone marrow, joint fluid, cerebrospinal fluid, urine, lymphatic tissue and other cultures. The positive rate of blood, bone marrow and joint fluid is higher in the acute stage and lower in the chronic stage.
Diagnosis and differential diagnosis
(I) Diagnosis
Diagnosis should be made by combining epidemiological history, clinical manifestations and laboratory tests.
1.Suspected cases
Suspected cases are those who meet the following criteria.
1.1 Epidemiological history: history of close contact with livestock or livestock products, brucella cultures, etc. before the onset of the disease, or residents living in areas where brucellosis is endemic, etc.
1.2 Clinical manifestations: fever, malaise, excessive sweating, muscle and joint pain, or accompanied by enlargement of liver, spleen, lymph nodes and testicles, etc.
2. Clinical diagnosis of cases
Suspected cases with positive immunological examination item 1 (primary screening test).
3.Confirmed cases
Suspected or clinically diagnosed cases with one or more positive immunological examination items 2, 3 and 4 and/or isolation of Brucella.
4.Covert infection cases
Epidemiological history, meeting the criteria of immunological and pathogenic examination of confirmed cases, but without clinical manifestations.
(II) Differential diagnosis
1.Typhoid fever, paratyphoid fever
Patients with typhoid fever and paratyphoid fever have persistent high fever, indifferent expression, slow relative pulse, skin rose rash, and hepatosplenomegaly as the main manifestations without muscle and joint pain, excessive sweating and other manifestations of brucellosis. Laboratory tests are positive for serum fertilizer reaction, positive culture for S. typhi, and negative for specific tests for brucellosis.
2.Rheumatic fever
Both brucellosis and rheumatic fever can show fever and wandering arthralgia, but rheumatic fever can be seen as rheumatic nodules and erythema, mostly combined with heart damage, while hepatosplenomegaly, orchitis and neurological damage are extremely rare. Laboratory tests are positive for anti-streptococcal hemolysin “O” and negative for specific tests for brucellosis.
3.Rheumatoid arthritis
Chronic brucellosis and rheumatoid arthritis both have severe joint pain, with recurrent attacks and intensification on cloudy days. Rheumatoid arthritis mostly has a history of rheumatic fever, lesions are mostly seen in large joints, joint cavity effusion is rare, joint deformity usually does not occur, often combined with heart damage, serum anti-streptococcal hemolysin “O” titer is increased, negative laboratory tests specific for brucellosis can help to differentiate.
4.Other
The acute phase of brucellosis should be distinguished from tuberculosis, sepsis, etc. The chronic phase should also be distinguished from other joint damage diseases and neurological disorders.