Brucellosis Overview Quiz

Brucellosis

• Caused by Brucella group of organisms.
• Gram-negative aerobic cocco-bacilli.
• 3 serotypes infect humans.

Serotypes

• B. abortus → cattle

• B. melitensis → goats and sheep

• B. suis → pigs

• Brucella possesses two antigens:

  • A → B. abortus and B. suis
  • M → B. melitensis

Transmission

• A zoonotic and occupational disease.
• Transmission routes include:
  • Gastrointestinal tract (GIT)
  • Direct contact
  • Respiratory tract
  • Congenital
  • Human milk
  • Infected blood

Pathology

• Infection involves the nasopharynx or GIT, leading to regional lymph nodes and the reticuloendothelial system (RES).
• Brucella organisms are strictly intracellular, explaining the chronic and treatment-resistant nature of the infection.
• Two types of reactions occur:
  • Hypersensitivity reaction →granulomas
  • Antibody reaction → primary (IgM) response (e.g., Widal test) or secondary (IgG) response (e.g., Coomb's test)
• Mononuclear cells distortion and rupture exhibit periodicity.

Presentation

• Incubation period (IP) is 2-4 weeks.
• 1. Asymptomatic
• 2. Acute onset (rapid or insidious) with nonspecific symptoms such as fever, drenching sweats, headache, arthralgia, and arthritis (especially back tenderness).

Clinical Features

• Fever (stepladder, intermittent, periodic, 2-4 weeks per cycle).
• Splenomegaly (27-50%).
• Lymphadenopathy.
• Chronic cases show nonspecific symptoms like headache, sweating, backache, mental symptoms, and hepatosplenomegaly (always present).

Complications

• Skeletal involvement → predilection for the lumbar region, destruction of vertebrae and intervertebral discs, leading to sciatica, cauda equina lesions, paraplegia, sacroilitis (common).
• Brucella endocarditis → serious (affecting aortic and mitral valves).
• Liver abscesses
• Central Nervous System (CNS) involvement → neurobrucellosis (depression, suicidal tendencies).
• Genitourinary (GU) tract involvement → orchitis and pyelonephritis.

Causes of Death

• Suicide
• Infective endocarditis
• Liver failure

Investigations

• General investigations:
  • Normocytic normochromic anemia
  • White blood cell count (WBC) normal or reduced
  • Elevated erythrocyte sedimentation rate (ESR)
  • Liver function tests (LFT) normal or elevated
• Specific investigations:
  • Isolation of organism from blood (difficult, 4-6 weeks to get result, 10-85% positivity).
  • Bone marrow (BM) culture (90%).
  • Organism isolation from urine, pus, or cerebrospinal fluid (CSF) (45%).
  • Liver biopsy (microgranulomas)
  • Widal test (detects IgM for recent infection).
  • Coomb's test (detects IgG and not indicative of recent infection).
  • ELISA (distinguishes between IgM and IgG).
  • Polymerase Chain Reaction (PCR) (detects Brucella antigen).
  • Brucella skin test.

Treatment

• Standard treatment options:
  • Streptomycin (STM) 1g for 2-3 weeks + doxycycline 100 mg twice daily for 6 weeks (6% relapse rate)
  • Rifampicin 600mg before breakfast for 6 weeks + doxycycline 100 mg twice daily for 6 weeks (14% relapse rate)
  • Cotrimoxazole + Gentamicin (safe during pregnancy: Rifampicin 600mg daily x 6 weeks)

Prevention

• Boil or pasteurize milk.
• Avoid raw milk products.
• Vaccinate animals.