Brucellosis

Topic Overview

Brucellosis

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Definition

• Brucellosis, also known as:

  • Undulant Fever

  • Mediterranean Fever

  • Malta Fever

• A zoonotic infection caused by bacteria of the genus Brucella

• These are Gram-negative aerobic coccobacilli infecting both humans and animals

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Epidemiology

• A widespread infection affecting:

  • Cattle

  • Sheep

  • Goats

  • Pigs

• Main causative species:

  • Brucella abortus → cattle

  • Brucella melitensis → sheep and goats

  • Brucella suis → pigs

• Human cases are common in:

  • Mediterranean countries

  • Middle East

  • Africa

  • Asia

  • Latin America

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Pathophysiology

• Humans acquire infection via:

  • Ingestion of contaminated milk/dairy products

  • Direct contact with infected animals

• High-risk occupations:

  • Veterinarians

  • Farmers

  • Animal handlers

• The organism targets the reticuloendothelial system, leading to:

  • Granulomatous tissue response

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Clinical Features

General Systemic Features

• Incubation period: 5–30 days

• Symptoms:

  • Intermittent (undulating) fever

  • Headache

  • Backache

  • General malaise

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Organ Involvement

 

 

 

4

• Lymphadenopathy (~50%)

• Splenomegaly (~50%)

• Hepatomegaly (~25%)

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Cutaneous Manifestations

 

 

 

4

• Seen in ~5% of cases

• Types of lesions:

  • Morbilliform rash

  • Scarlatiniform rash

  • Roseolar exanthem

  • Papular lesions

  • Bullous lesions

  • Hemorrhagic lesions

  • Erythema multiforme-like nodules (often on legs)

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Contact Brucellosis

 

 

 

4

• Seen in veterinary surgeons / exposed individuals

• Features:

  • Localized pruritus

  • Erythema and wealing

  • Follicular papules, vesicles, or pustules

• Typically heal within 10–14 days

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Differential Diagnosis

• Fevers of unknown origin (FUO) → always consider brucellosis

• Other conditions:

  • Herpes simplex / zoster

  • Orf virus infection

  • Poxvirus infections

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Investigations

Laboratory Diagnosis

• Relative lymphocytosis without leukocytosis

• Agglutination titres:

  • ≥ 1:100 → suspicious

  • ≥ 1:300 → diagnostic

• Blood cultures / PCR → confirm diagnosis

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Histological Findings

 

 

 

4

• Intense inflammatory changes

• May show granuloma formation

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Management

1. First-Line Treatment

• Doxycycline + Rifampicin for ≥6 weeks

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2. Second-Line Options

• Co-trimoxazole

• Tetracycline + Streptomycin

• Oxytetracycline + Gentamicin (children >8 years)

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3. Alternative Antibiotics

• Ciprofloxacin and others

• Role still under evaluation

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Treatment Ladder

First-line

• Doxycycline

• Rifampicin

Second-line

• Co-trimoxazole

• Tetracycline + Streptomycin

• Oxytetracycline + Gentamicin

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Prognosis

• Variable disease course

  • Typical duration: 3–4 months

• Possible outcomes:

  • Acute fulminant disease

  • Chronic persistent infection

• Relapses common with inadequate therapy

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Key Point

✔ Brucellosis is a zoonotic granulomatous infection
✔ Presents with undulating fever + systemic + occasional skin manifestations
✔ Diagnosis: Serology + culture/PCR
✔ Requires prolonged combination antibiotic therapy for cure