Brucellosis

Last updated: September 2022

 

Brucellosis is a zoonosis that mainly affects livestock animals. 

 

The main routes of transmission to humans are: 

• digestive, by ingestion of unpasteurized milk (or unpasteurized milk products) from an infected animal;
• cutaneous, by direct contact with infected animals or carcasses of infected animals. 

 

Brucellosis is caused by bacteria of the genus Brucella, particularly B. melitensis (sheep and goats), B. abortus (cattle), B. suis (pigs).

 

The disease is found worldwide and mainly in rural areas. 

After primary infection relapses may occur (5 to 15% of cases, even months after end of initial treatment) or the infection may become chronic.

Clinical features

Acute form (primary infection)

• Remittent or intermittent fever (39-40 °C), associated with several signs or symptoms: chills, night sweats, joint and muscle pain, weight loss, fatigue, malaise, headache; adenopathies (particularly in children).
• May be associated with: non-specific gastrointestinal disorders, cough, hepato and/or splenomegaly, arthritis (knee), orchitis.

 

Diagnosis is difficult because of the broad spectrum of fluctuating and non-specific clinical manifestations. In patients with unexplained fever, brucellosis should be considered when risk factors are present: consumption of unpasteurized milk products; exposure to livestock (e.g. livestock farmers, veterinarians, butchers, slaughterhouse workers).

Localised form 

Primary infection may progress to localised infection (even several months or years later), mainly:

• osteoarticular: sacroiliac joint and often particularly lower limbs joints;  spine (intervertebral disk infection, vertebral osteomyelitis)
• genito-urinary: orchitis, epididymitis 
• pulmonary: bronchitis, pneumonia, pleurisy 
• neurological : meningitis, encephalitis, polyneuritis

Paraclinical investigations

Laboratory

• Blood culture is the gold standard for diagnosis. It is positive only in the acute phase. The bacteria grow slowly (7 to 21 days).
• Serological tests (Rose Bengal, Wright agglutination test, indirect immunofluorescence, ELISA, etc.) provide presumptive diagnoses.
• In the event of neurological signs or meningitis, lumbar puncture shows clear cerebrospinal fluid (CSF) that may contain high white blood cell count; high protein concentration in CSF; low CSF glucose.
• Rule out malaria in endemic regions (rapid test).
• Exclude tuberculosis if cough > 2 weeks (sputum smear microscopy).

Radiography 

• Joint pain (hips, knees, ankles, vertebrae, sacroiliac joint): small erosions or destruction or joint space narrowing. Often involves the spine, particularly the lumbar spine, causing spondylodiskitis.
• Pulmonary signs: chest x-ray often normal. There may be consolidation, nodules, lymphadenopathy, or pleural effusion.

Treatment

Check national recommendations on antibiotic therapy. For information:

 

co-trimoxazole PO for 6 weeks
Children < 8 years: 20 mg SMX + 4 mg TMP/kg (max. 800 mg SMX + 160 mg TMP) 2 times daily

 

doxycycline PO for 6 weeks 
Children ≥ 8 years and < 45 kg: 2 to 2.2 mg/kg (max. 100 mg) 2 times daily

Children ≥ 45 kg and adults: 100 mg 2 times daily

 

 

rifampicin PO for 6 weeks
Children: 15 to 20 mg/kg (max. 600 mg) once daily
Adults: 600 to 900 mg once daily

 

gentamicin IM for 2 weeks
Children and adults: 5 mg/kg once daily

 

streptomycin IM for 2 weeks
Adults: 1 g once daily

 

For localised forms of the infection, same treatment but for a period of 6 weeks to 4 months depending on the focus.

Prevention

• Washing of hands and clothing if in contact with animals.
• Boil milk, avoid ingestion of unpasteurized milk products, cook offal thoroughly.