In a farmer/shepherd who consumes unpasteurised dairy and presents with sub‑acute fever, night sweats, fatigue, weight loss, arthralgias, and hepatosplenomegaly, what are the typical clinical features, diagnostic criteria, and first‑line treatment for brucellosis?

Clinical Presentation of Brucellosis

In a farmer or shepherd with unpasteurized dairy consumption presenting with subacute fever, night sweats, fatigue, weight loss, arthralgias, and hepatosplenomegaly, brucellosis should be suspected and confirmed with extended blood cultures and serology, then treated with doxycycline 100 mg every 12 hours plus rifampicin 600 mg every 24 hours for 6 weeks. 1, 2

Typical Clinical Features

Constitutional Symptoms

• Fever is almost invariable (present in 91% of cases), often presenting as subacute or chronic rather than acute 1, 3
• Night sweats, fatigue, and malaise occur in approximately 77% of patients 3
• Weight loss is a common feature of the chronic systemic illness 4

Musculoskeletal Manifestations

• Arthralgias are present in 77% of cases, representing one of the most frequent complaints 3
• Joint involvement can progress to frank arthritis in some patients 4

Organomegaly

• Hepatosplenomegaly is a characteristic finding that should prompt consideration of brucellosis in the appropriate epidemiologic context 1, 5
• Hepatomegaly and splenomegaly are significantly more common in brucellosis patients compared to other febrile illnesses (p < 0.001 and p = 0.018, respectively) 5

Cutaneous Manifestations

• Skin lesions may occur in combination with fever, lymphadenopathy, and hepatosplenomegaly 2
• The presence of characteristic rash with systemic symptoms should prompt serologic testing 2

Epidemiologic Risk Factors

Occupational and Dietary Exposures

• Consumption of unpasteurized milk and dairy products is the most common transmission route globally, present in 88% of pediatric cases 1, 6, 3
• Contact with livestock (cattle, sheep, goats) represents the primary occupational risk 1, 4
• Farmers, shepherds, veterinarians, slaughterhouse workers, and butchers are at highest risk 4, 7
• Family history of brucellosis increases risk significantly (aOR 9.19,95% CI 1.98-42.54) 5

Geographic Considerations

• Brucellosis remains endemic in the Middle East, Mediterranean, North Africa, and parts of sub-Saharan Africa 1
• The disease is uncommon in the United States (average 113 cases annually), but remains prevalent in regions with unpasteurized dairy consumption 6

Diagnostic Criteria

Serologic Testing

• Extended blood cultures and serology are the recommended diagnostic approach 1
• Coombs Wright test has the highest sensitivity at 92%, followed by 2-mercaptoethanol (2-ME) test at 85% 3
• Standard Wright agglutination test is positive in 67% of cases 3
• IgM antibodies appear early and are typically detectable at clinical presentation, usually by the second week of illness 8
• Testing paired serum specimens 2-3 weeks apart demonstrating four-fold or greater increase in titer confirms acute infection 8

Culture Methods

• Blood culture remains the gold standard, with highest sensitivity from bone marrow specimens (31% positive rate vs. 30% for blood) 8, 3
• Blood cultures have highest yield within the first week of symptom onset 1
• Cultures should be handled as Biosafety Level 3 pathogens to prevent laboratory-acquired infections 9

Laboratory Abnormalities

• Anemia occurs in 65% of cases 3
• Lymphocytosis is present in 51% of patients 3
• Elevated erythrocyte sedimentation rate (86%) and C-reactive protein (67%) are prominent findings 3
• Low body mass index is more common in brucellosis patients (p = 0.032) 5

First-Line Treatment

Standard Antibiotic Regimen

• Doxycycline 100 mg every 12 hours plus rifampicin 600 mg every 24 hours for 6 weeks is the WHO-recommended first-line treatment 2
• This combination leads to rapid resolution of both systemic and cutaneous manifestations 2
• Treatment should be discussed with an infectious disease specialist 1

Alternative Regimens

• Trimethoprim-sulfamethoxazole combined with rifampicin was used in 56% of pediatric cases, with median treatment duration of 12 weeks 3
• Longer treatment courses (up to 24 weeks) may be necessary in complicated cases 3

Treatment Challenges and Relapse

• Relapse occurs in approximately 21% of cases, necessitating careful follow-up 3
• Antibiotic treatment is often challenging due to intracellular survival of Brucella in macrophages 7
• Treatment failure is more likely without adequate duration of dual antibiotic therapy 4

Critical Clinical Pitfalls

Diagnostic Delays

• Non-specific symptoms (headache, gastrointestinal complaints, dry cough) can mislead clinicians away from the diagnosis 1
• Full blood count and liver function tests may be normal or show non-specific derangements 1
• Always suspect brucellosis in febrile patients with hepatosplenomegaly and history of unpasteurized dairy consumption or livestock contact 1, 5

Laboratory Safety

• Failure to handle specimens as BSL-3 pathogens can result in laboratory-acquired infections requiring 24-week monitoring and prophylactic antimicrobials 6, 9
• Laboratory personnel exposed to unsuspected Brucella cultures require immediate prophylaxis with rifampicin and doxycycline 9

Serologic Interpretation

• Cross-reactivity with other bacterial antigens can cause false-positive results 8
• In endemic areas, background seroprevalence must be considered when interpreting results 8
• IgM antibodies may persist for 3-12 months, complicating distinction between acute and past infection 8