Brucellosis

Cause:

• Brucella
• Most virulent cause of brucellosis: B. melitensis .
• a zoonotic diseases
• mediterranean fever/Malta/undulant fever.

Source:

• Sheep, goats,camels.

Route of transmission:

• Occupational exposure
• Infected meat (slaughterhouse workers)
• placentae of infected animals (farmers, veterinarians)
• Ingestion of untreated milk or milk
• products, raw meat (blood)
• inhalation
• transplacental
• during breasffeeding
• during sexual activity.

Symptoms

• Fever, chills, diaphoresis, headaches.
• Pancarditis
• Sleep disturbances
• lymphadenopathy
• Hepatosplenomegaly
• GBS syndrome
• Abortion or IUD during pregnancy are other important findings.
• Musculoskeletal pain.
• Death is usually a consequence of cardiac involvement.

Immunity

• Cell-mediated.

Diagnosis

Laboratory diagnosis of Brucellosis

Specimens

• Blood
• Biopsy material from lymph nodes, bone
• Serum for serological tests.

Culture

• Blood culture is the most definitive method for the diagnosis of Brucellosis.
• Castaneda method of blood culture recommended.
• Bone marrow culture yield a higher rate of isolation
• Remain positive long after the blood culture has become negative.

Serological tests

For Acute cases:

• Standard agglutination (SAT) test done
• Shows prozone phenomenon
• SAT also +ve in cholera, tularemia, yersinia, and immunization

For Chronic:

• Complement fixation test.

Explanation:

• Ig M antibody
• levels rises during the first week of acute illness
• Peaks at 3 months.
• Ig G antibody levels
• rises in about 3 weeks after the onset of acute illness
• Peaks at 6-8 weeks
• Remain high during chronic disease.
• Ig A levels parallel the Ig G levels.

Role

• Differentiate active from inactive Brucellosis.
• Determining the adequacy of antibiotic therapy
• Adequate therapy reduces the IgG antibody level but not the IgM antibody level.

• IgM immunoglobulin is inactivated by treating with  (2-ME) .
• The IgG immunoglobulin is resistant to depolymerization by 2- mercaptoethanol (2ME).

Polmerase chain reaction (PCR)

• PCR is more sensitive and quicker than blood culture. 

For diagnosing animal infection –

• Rapid plate agglutination
• Rose Bengal card
• milk ring test

Treatment

• Adults: Streptomycin + doxycycline.
• Alternative rifampin + doxycycline.
• Children, Pregnant women or who cannot tolerate tetracycline-Cotrimoxazole given.