• Four species of brucella cause human disease: B. abortus (cattle), B. melitensis (goats and sheep), B. suis (hogs), and B. canis (dogs).
• Organisms are small fastidious gram-negative coccobacilli.

• While humans are not a usual host, infection with Brucella species may occur following contact with infected domesticated or wild animals.
• Subsequently, the bacterium replicates inside the phagocytic cells of the host.
• Routes of infection include abraded skin, oral membranes, respiratory tract, or conjunctiva inoculation.
• Virulence factors in the bacteria and host factors (nutritional, immunological) may predict severity of infection.
• Incubation period is usually 3 to 4 weeks.

• Approximately 200 cases are reported in the United States yearly; less than 10% in children.
• Brucellosis may be acquired from non-pasteurized dairy products, particularly in Mexico, the Mediterranean, the Far East, and South America.
• Veterinarians are occasionally inoculated with live vaccine (via needle or airborne routes) during occupational accidents, producing mild disease.

• Localized disease may result in osteomyelitis (usually vertebral), arthritis, splenic abscess, epididymoorchitis, meningoencephalitis, pleural effusion, pneumonia, and bacterial endocarditis.
• Chronic brucellosis may occur more than 1 year after the onset of disease. A subset of these patients have no objective evidence of infection.
• An erythematous macular, papular, or pustular rash may be seen on the hands and arms of veterinarians following the removal of placentas from infected animals.

• Even prior to the advent of treatment with antibiotics, most patients recovered from a Brucella infection within 3 months.
• If the duration of illness with appropriate treatment exceeds 2 months, other diagnoses should be considered.

• Diagnosis should be considered when evaluating persons with evidence of localized or systemic infection and risk of contact through domestic animals (especially cattle and swine).
• More common diseases with similar presentations include:
  • Influenza
  • Infectious mononucleosis
  • Tuberculosis
  • Leptospirosis
  • Toxoplasmosis
  • Rheumatic fever
  • Systemic lupus erythematosus
  • Viral hepatitis
  • Disseminated gonococcal disease

• Infection with brucellosis is often asymptomatic.
• Onset may be insidious, although certain species produce a severe form.
• Low-grade fever?
• Fatigue?
• Headache?
• Malaise?
• Weakness?
• Sweats?
• Chills?
• Arthralgias?
• Myalgias?
• Abdominal pain?

• Splenomegaly
• Lymphadenopathy
• Hepatomegaly.

Test: Culture of the Brucella species
Significance: Can be isolated from the blood, lymph nodes, spleen, liver, or bone marrow.

Test: Blood culture
Significance: More likely to be positive early in infection, and usually requires 1 to 3 weeks of growth time.

Test: Culturing Brucella specimens
Significance: Can be hazardous to laboratory personnel, and should be labeled “Caution: Possible Brucellosis.”

Test: Serologic evidence
Significance: Infection can be demonstrated with the serum agglutination test (SAT), prepared from B. abortus antigens. An early light peak, followed by rising lag titers is usual. A single titer of 1:160 is significant, although not diagnostic.

• Course of the illness can be shortened and incidence of complications reduced by treatment with one of the tetracyclines.
• Usual dosage is administered for 4 to 6 weeks.
• Tetracyclines should be avoided in pregnant women and children less than 8 years old.
• Trimethoprim-sulfamethoxazole can be used in children safely in its usual dosage.
• Streptomycin has traditionally been added to a tetracycline, but may not be necessary.
• Abscesses should be surgically drained.
• Splenectomy may be required in patients with splenomegaly and multiple relapses.

• Contact precautions are necessary for the patient with draining wounds.

• Domesticated animals can attain immunity to Brucella through vaccination with a live attenuated vaccine.
• Pasteurization of milk and milk products prevents infection.
• Meat workers, veterinarians, and cattle workers should reduce risk by appropriate bandaging of wounds, and by wearing gloves and goggles.

Q: What are the other names for brucellosis?
A: Malta fever, Mediterranean fever, and Undulant fever

Q: What is the cause of relapses?
A: Usually caused by discontinuing antibiotics prematurely.