Brucellosis

Brucellosis (undulant fever) is a zoonotic infection caused by Brucella, characterized by prolonged fever, sweating, fatigue, arthralgia, and hepatosplenomegaly/lymphadenopathy. In China, B. abortus and B. melitensis are the main pathogens, endemic in pastoral areas of the northwest, northeast, Qinghai-Tibet Plateau, and Inner Mongolia.

Common Symptoms

Fever of unknown origin; irregular fever; lymphadenopathy

Causes and Pathogenesis

Bacilli enter via skin/mucosa, reach regional lymphatics, are phagocytosed, and form foci if not killed; they then overwhelm lymphatic barriers into the blood, continuing to grow, die, and release endotoxin causing bacteremia and toxemia. One mg of endotoxin can raise temperature to 40.5°C. With normal immunity, T cells, macrophages, and specific antibodies clear the infection; if not, bacteria spread via blood (especially in macrophages) to organs causing metastatic foci and relapses. In the chronic phase, bacteria localize or lesions result from allergy. Brucella is intracellular, making eradication difficult. Pathology is widespread, especially in the mononuclear-phagocyte system; acute phase shows diffuse cellular proliferation, chronic phase shows non-caseating granulomas of epithelioid cells, macrophages, plasma cells, and lymphocytes (resembling sarcoidosis), with variable cardiovascular, musculoskeletal, genital, and nervous system involvement.

Treatment

Symptomatic and etiological treatment

Preventive Measures

Integrated measures centered on livestock vaccination. 1. Control sources: periodic quarantine, slaughter sick animals, separate flocks, and vaccine immunization. S19 vaccine (injection) protects sheep/cattle but causes abortion in pregnant animals; S2 vaccine in drinking water is effective and labor-saving; M5 aerosol vaccination suits water-rich areas. Personal protection is needed during vaccination. Vaccination interferes with serodiagnosis; RB5 strain may avoid this. Patients need isolation and excreta disinfection. 2. Cut transmission: bury and disinfect livestock afterbirth; pasteurize/boil milk; disinfect hides (1-5 months natural storage, sun, chemical, 60Co gamma); cook meat; compost manure; protect water supplies; wear protective clothing (work clothes, masks, hats, aprons, gloves, boots) when handling sick animals; wash hands after work; no eating during work.

Department to Visit

It is recommended to visit the Infectious Diseases department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.