Brucella abortus primarily infects cattle; Brucella melitensis primarily infects sheep and goats. B. melitensis is more pathogenic for humans, causing more severe, often chronic disease, and is the leading cause of human brucellosis. Both transmit via contact with infected animals or unpasteurized dairy. Control differs by species-specific reservoir management and vaccines (e.g., S19/RB51 for abortus, Rev-1 for melitensis).

If Brucella is positive, seek prompt medical evaluation and start specialist-guided antibiotic therapy—typically a combination regimen for several weeks—to clear infection and prevent relapse. You may need additional treatment or hospitalization for severe or focal disease (bones, joints, heart). Pregnant patients require different regimens. Avoid unpasteurized dairy, report occupational exposure, and complete follow-up testing to confirm cure and monitor for relapse.

Brucella melitensis causes brucellosis, a zoonotic systemic infection transmitted mainly from infected sheep and goats. It produces undulating fever, sweats, malaise, anorexia, weight loss, myalgia, arthralgia, headache, and hepatosplenomegaly. Complications include osteoarticular disease, endocarditis, and genital involvement such as orchitis or epididymitis; chronic or relapsing infection can occur without prompt diagnosis and prolonged antibiotics.

Brucella abortus causes brucellosis — a zoonotic bacterial infection. In cattle it produces bovine brucellosis, notably abortions and infertility; in humans it causes systemic brucellosis (undulant fever) with fever, sweats, fatigue, joint and muscle pain, and potential chronic complications. Transmission is via contact with infected animals, aborted tissue, or unpasteurized dairy; diagnosis requires lab testing and antibiotics.

Brucella melitensis is primarily found in sheep and goats (and occasionally camels). It is endemic in parts of the Mediterranean, Middle East, Africa, South and Central Asia, and Latin America. Human infection usually follows contact with infected animals or tissues, or consumption of unpasteurized milk and cheese. Occupational risks include farmers, veterinarians and abattoir workers handling infected animals or birthing products.

Brucellosis classically causes undulant fever — an intermittent, relapsing fever that rises and falls over days or weeks. Patients often have low-grade fever with periodic high-temperature spikes, especially in the evenings, accompanied by sweats (often night sweats), malaise, arthralgia and fatigue. The pattern can be prolonged and recurrent without adequate treatment.