Brucellosis: cause, transmission, symptoms, diagnosis and prevention

Cause and biology

Several Brucella species infect different host animals. For example, B. melitensis commonly infects goats and sheep, B. abortus is associated with cattle, B. suis with pigs and B. canis with dogs. These bacteria invade cells of the immune system and can survive intracellularly, which helps explain why infections may become persistent or recur. Laboratory diagnosis typically relies on culture, serology, or molecular tests that detect the organism or immune response.

Transmission and risk factors

Human exposure usually comes from direct contact with infected animals or animal products, especially consumption of unpasteurized milk and dairy products. Handling birth tissues or aborted fetuses, slaughtering, and veterinary work are recognized occupational risks. Less commonly, transmission has occurred through contaminated meat (meat), inhalation of aerosols, accidental laboratory exposure, and, rarely, person-to-person routes such as breastfeeding or blood transfusion. Public-health guidance emphasizes pasteurization, protective equipment and vaccination of animals to reduce human cases. The term zoonosis is often used when discussing these transmission pathways.

Clinical features and complications

Symptoms typically begin days to weeks after exposure and may include fever, sweats (especially night sweats), malaise, joint and back pain, and weight loss. Some patients develop localized complications such as spondylitis, arthritis, endocarditis or involvement of the nervous system. Chronic or relapsing forms can occur when treatment is delayed or incomplete; appropriate antimicrobial therapy reduces long-term complications.

Diagnosis, treatment and prevention

Diagnosis combines clinical suspicion with laboratory tests (culture, serology, PCR). Because Brucella are hazardous to handle, laboratories use special precautions. Treatment requires combination antibiotic regimens over several weeks to months to eradicate intracellular organisms; relapse is a recognized risk without adequate therapy. Prevention focuses on animal herd health (vaccination and testing), food safety (pasteurization of milk and proper cooking of meat), and occupational controls for veterinarians, farmers and abattoir workers.

History and notable facts

The disease was long known by place-based names such as Malta fever or Mediterranean fever. British physicians described the illness among troops and local populations in places like Malta during 19th-century conflicts; its identification as a bacterial disease followed work during the Crimean era (Crimean War) and later investigations by clinicians and microbiologists. Dr. David Bruce and colleagues linked the clinical syndrome to the causative organism. Military and public-health interest (military) helped spur early research. For contemporary guidance on management and public-health measures see recognized clinical resources and local health authorities (human health, food safety, microbiology, taxonomic, disease overview, zoonotic disease info, historical accounts).