Brucellosis

Dr. Nada Abdelrahman Brucellosis is a highly contagious bacterial zoonosis, i.e., a disease which spreads from animals to humans. It is a major public health problem in many countries, especially in the Kingdom of Saudi Arabia (KSA).

• Caused by ingestion of unsterilized milk or meat from infected animals or close contact with their secretions (sheep, cattle, goats, pigs).
• Occupational hazard for veterinarians and slaughterhouse workers.
• Examples of other zoonotic diseases: rabies, West Nile virus infection, leptospirosis.

Other Names:

• Malta fever, Maltese fever
• Mediterranean fever
• Rock fever, or undulant fever

Epidemiology

Etiologic Agent: Caused by Gram-negative bacteria called Brucella. Four types can infect humans:

• Brucella Abortus (Cattle)
• Brucella Canis (Dogs)
• Brucella Melitensis (Sheep & Goats - commonest in KSA)
• Brucella Suis (Pigs)

Prevalence is related to the prevalence of domestic animals:

1. B. abortus - mainly cattle
2. B. melitensis - sheep & goats (most common worldwide)
3. B. suis - pigs
4. B. canis - dogs
5. B. ovis - sheep (not a human pathogen)
6. B. neotomae - desert wood rat (not a human pathogen)

Occurrence in KSA: Brucellosis is endemic (very common) in:

• Mediterranean countries (Malta, Greece, Cyprus)
• Arabian Gulf
• Asia
• Latin America
• KSA

Why Brucella is Common in KSA:

1. Close contact with camels, sheep, etc. in desert communities.
2. Custom of drinking unpasteurized camel milk in deserts & villages.

Organism

• Gram-negative, intracellular coccobacilli bacteria.
• Non-motile, non-capsulated, non-spore forming.
• Brucella spp. are intracellular organisms that survive for long periods within the reticulo-endothelial system.
  • Formation of non-caseating granulomas.
  • This explains the disease chronicity and tendency to relapse.

Transmission

Routes of Transmission:

• Oral: Unpasteurized milk & products, raw milk or meat.
• Respiratory: Lab workers.
• Skin: Accidental penetration or abrasion.
• Other: Conjunctival, blood transfusion, transplacental, person-to-person (?).

At-Risk Individuals:

• Farmers
• Veterinarians

Clinical Features

Brucellosis is a systemic disease, and almost any system can be affected. It can present in acute or chronic forms, with symptoms persisting for months or years.

Most Common Symptoms:

• Body & joint pains
• Fatigue
• Fever
• Excess sweating (foul-smelling)

Other Features:

• Chronic ill health
• Hepatomegaly/splenomegaly
• Lymph node enlargement
• Gastrointestinal symptoms (nausea, vomiting, weight loss)
• Sacroiliitis (very characteristic)

Types of Fever: Acute Brucellosis:

• Incubation period: 1-3 weeks
• Mild, transient illness (B. abortus or canis)
• Toxic illness with multiple complications (B. melitensis)
• 50% have an abrupt onset over days.

Symptoms in brucellosis are nonspecific.

• 90% malaise, chills, sweats, fatigue.
• 50% myalgias, anorexia, and weight loss.
• Sacroilitis ( very characteristic)
• Others: arthralgias, cough, testicular pain, dysuria, ocular pain, or blurring of vision.
• Splenomegaly is present in 10% - 15%
• Painful Lymphadenopathy

Chronic Brucellosis:

• Fever can be intermittent or undulant, persisting for months or years.

Neurologic (Neurobrucellosis):

• Usually presenting as meningitis (1-2%)
• Encephalitis, radiculopathy & peripheral neuropathy, intracerebral abscesses
• Neck rigidity < 50%
• CSF
  • Lymphocytic pleocytosis (Same as TB)
  • (N) or low sugar
  • increase protein
  • Culture +ve < 50% - Differentiates TB/Bru
  • Agglutination +ve in >95% - Differentiates TB/Bru

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Diagnosis

1. Clinical features: CBC (Neutropenia, anemia, pancytopenia)
2. Serology (Rose Bengal test): Brucella agglutination test
3. Blood or tissue culture: Definitive diagnosis but time-consuming (> 2 months). Lymph node or bone marrow biopsy specimen and culture. Histopathology: non-caseating granulomas.
4. Polymerase Chain Reaction (PCR)

Serology

Main diagnostic method

• Serum agglutination test - most widely used
• Measures agglutination for IgG, IgM, IgA
• which level is diagnostic ??
  • 1 : 160 – non-endemic area
  • 1 : 320 - endemic area
  • or fourfold rise in titre

Treatment:

Treatment of Choice: Combination therapy has the best efficacy.

Standard Regimen: Oral Doxycycline daily for six weeks in combination with gentamycin injection for 1 week. Best management option

Alternative Regimen: Another option: Oral Doxy. + oral Rifampicin both for 6 wks

Bone disease: - Doxycycline + Rifampicin for 6 weeks + Gentamicin for 7 days, or - Ciprofloxacin + Rifampicin for 3 months.

Neurobrucellosis: Doxycycline + Rifampicin for 6 weeks + Ceftriaxone.

Endocarditis: - Surgical intervention - Doxycycline + Rifampicin + Co-trimoxazole + Gentamicin for 2-4 weeks.

Brucellosis in Pregnancy: Can cause maternal symptoms, abortion, and intrauterine fetal death.

• Treatment of choice:
  • Co-trimoxazole (sulfamethoxazole + trimethoprim) + Rifampicin for 4 weeks.
  • Weigh risk and benifits
  • Caution in the last week of pregnancy due to the risk of kernicterus.

Prevention

• Control of disease in domestic animals (immunization).
• Routine pasteurization of milk.
• Strict biosafety precautions in labs.
• Protective measures in slaughterhouses (wound dressing, protective glasses and clothing, prohibition of raw meat ingestion, use of immune individuals in high-risk areas).

Reference

Kumar & Clark’s Clinical Medicine, page 548.