Summary

Brucellosis is a systemic zoonotic infection caused by Brucella species, small Gram-negative coccobacilli. It is one of the most common zoonoses worldwide, particularly in endemic regions (Mediterranean, Middle East, Central Asia, Latin America). Transmission occurs through consumption of unpasteurised dairy products (especially cheese, milk) or direct contact with infected animals (cattle, goats, sheep, pigs). The hallmark clinical feature is undulant (wavelike) fever with drenching night sweats (classically described as having a "mouldy" or "hay-like" odour). Brucellosis is a great mimicker with protean manifestations, including musculoskeletal (sacroiliitis, spondylitis), genitourinary (orchitis), and neurological (neurobrucellosis) complications. Diagnosis is by blood culture (held for extended incubation) and serology (SAT, ELISA). Treatment requires combination antibiotic therapy for 6 weeks or longer to prevent relapse.

Key Facts

• Agent: Brucella species. B. melitensis (Goats/Sheep – most virulent), B. abortus (Cattle), B. suis (Pigs), B. canis (Dogs).
• Transmission: Ingestion of unpasteurised dairy, Inhalation (Lab workers, Farmers), Direct contact (Abortus material).
• Clinical Features: Undulant Fever, Night Sweats, Arthralgia/Arthritis, Hepatosplenomegaly, Orchitis, Sacroiliitis.
• Diagnosis: Blood Culture (Hold 21 days), Serology (SAT >1:160, Brucella ELISA).
• Treatment: Doxycycline + Rifampicin (6 weeks) OR Doxycycline + Streptomycin/Gentamicin.
• Complications: Spondylodiscitis, Neurobrucellosis, Endocarditis (High mortality).

Clinical Pearls

"Undulant Fever": The fever of brucellosis characteristically waxes and wanes over days to weeks. This undulating pattern gave the disease its alternative name.

"Mouldy Sweats": Patients classically describe their night sweats as having a peculiar "mouldy" or "straw-like" smell – a distinctive but inconsistent clue.

"Hold the Blood Culture": Brucella is slow-growing. Cultures should be held for 21 days or processed in a special system (BACTEC). Many cases are missed due to premature discarding of cultures.

"Cheese from Abroad = Think Brucellosis": Travel to endemic areas + consumption of local unpasteurised cheese + fever/arthralgia = High suspicion for Brucellosis.

Why This Matters Clinically

Brucellosis is often missed due to its non-specific presentation and the need for prolonged culture. In endemic regions, it is a major cause of morbidity. Untreated, it can cause chronic debilitating illness and serious complications (endocarditis, spondylitis).

Key Assessment Points

Differential Diagnosis

• Mortality (Uncomplicated): <1-2% with treatment.
• Mortality (Endocarditis): 20-80% (Often requires surgery).
• Relapse Rate: ~5-15% with combination therapy. Higher with monotherapy.
• Chronic Brucellosis: ~5-10% develop chronic symptoms (Fatigue, Vague pains).

Prognostic Factors

Prevention

Endemic Travel Advice (Patient Handout Content)

For travellers to endemic areas (Mediterranean, Middle East, Central/South America).

• Avoid unpasteurised milk, cheese, and ice cream.
• Choose pasteurised or UHT dairy products.
• Avoid local soft cheeses in markets unless certain of pasteurisation.
• If unwell after travel (Fever, Sweats, Joint pain), tell your doctor about your travel history and that you may have eaten unpasteurised dairy.

Laboratory Safety Considerations

Brucella is a significant biosafety hazard.

Occupational Brucellosis

Who is at risk?

Key Guidelines

Evidence for Treatment

Scenario 1:

• Stem: A traveller returns from Malta with undulant fever, drenching sweats, and hepatosplenomegaly. They ate local soft cheese. What is the likely diagnosis and how would you confirm it?
• Answer: Brucellosis. Confirm with Blood Culture (Hold 21 days) and Brucella Serology (SAT ≥1:160 or ELISA).

Scenario 2:

• Stem: A farmer presents with chronic back pain and fever. MRI shows L4/L5 disc space narrowing and endplate erosion. Brucella serology is positive. What is the diagnosis and treatment?
• Answer: Brucellar Spondylodiscitis. Treatment: Doxycycline + Rifampicin +/- Aminoglycoside for 3-6 months.

Scenario 3:

• Stem: Why is combination therapy essential in brucellosis?
• Answer: Brucella is an intracellular pathogen. Monotherapy has high relapse rates (>30%) because antibiotics cannot adequately penetrate macrophages or clear bacteria. Combination therapy with intracellularly-active drugs (Doxycycline, Rifampicin, Aminoglycosides) for prolonged duration reduces relapse.

Scenario 4:

• Stem: A lab technician develops fever after handling a sample. What is the likely pathogen and what safety concern arises?
• Answer: Brucella. Brucellosis is a significant laboratory-acquired infection (Aerosol hazard). Handle suspected samples with Biosafety Level 3 precautions. Notify infection control.

Scenario 5:

• Stem: A man with brucellosis develops a new murmur and embolic phenomena. What complication has occurred?
• Answer: Brucellar Endocarditis. This is the main cause of death in brucellosis. Requires prolonged triple antibiotics and often valve surgery.

What is Brucellosis?

Brucellosis is an infection caused by bacteria called Brucella. You can catch it by eating unpasteurised dairy products (like some soft cheeses or milk) or by direct contact with infected animals (cattle, goats, sheep).

What are the symptoms?

• Fever that comes and goes (undulant fever).
• Drenching night sweats.
• Tiredness, Muscle and joint pains.
• Swollen liver or spleen.

How is it treated?

Brucellosis is treated with a combination of antibiotics for at least 6 weeks. Taking only one antibiotic or stopping too early can cause the infection to come back.

Can it be prevented?

• Avoid unpasteurised dairy products, especially when travelling.
• Farm workers and vets should use protective equipment when handling animals.

Key Counselling Points

1. Complete Your Antibiotics: "Stopping early causes relapse. The full 6-week course is essential."
2. Avoid Unpasteurised Dairy: "This is the most common way to catch brucellosis when travelling."
3. Occupational Risk: "If you work with animals, use protective gloves and avoid contact with birthing materials."
4. Follow-Up: "We'll need to check that the infection has cleared and hasn't come back."

Patient FAQs

Common Clinical Pitfalls

Spondylodiscitis: Key Points

Most common focal complication.

Endocarditis: Key Points

Rare but MAIN CAUSE OF DEATH.

• Named after Sir David Bruce: British military physician who identified Brucella melitensis in Malta (1887) as the cause of "Malta Fever" among British soldiers.
• Alice Evans (1918): American microbiologist who demonstrated that human brucellosis could be caused by B. abortus (from cattle), leading to milk pasteurisation advocacy.
• Eradication Programs: Successful bovine brucellosis eradication in many developed countries has made human disease rare.