Brucellosis

• What is Brucellosis
• Statistics on Brucellosis
• Risk Factors for Brucellosis
• Progression of Brucellosis
• Symptoms of Brucellosis
• Clinical Examination of Brucellosis
• How is Brucellosis Diagnosed?
• Prognosis of Brucellosis
• How is Brucellosis Treated?
• Brucellosis References

What is Brucellosis

Brucellosis is a zoonotic (animal linked) infection transmitted from animals to humans by ingestion of infected food products (such as unpasteurised milk and cheese), direct contact with an infected animal, or inhalation of aerosols. This last method of transmission is remarkably efficient given the relatively low concentration of organisms (as few as 10-100 bacteria) needed to establish infection in humans and has brought renewed attention to this old disease as a potential biological warfare agent.

Statistics on Brucellosis

In most western countries, frequency of Brucellosis infection is related to the number of infected animals. Brucellosis infected animals are considered rare, and pasteurization of milk has eliminated this method of contraction, thus Brucellosis infection generally occurs via occupational exposure (cattlemen, veterinarians, slaughterhouse workers). The incidence of brucellosis is approximately 200 per year or 0.04 per 100,000.
Frequency of brucellosis varies across nations but obviously is higher in more agrarian societies and in places where handling of animal products and dairy products is less stringent. The highest incidence of brucellosis is observed in the Middle East, Mediterranean region, China, India, Peru, and Mexico.
Mortality from brucellosis is rare and usually is secondary to the development of endocarditis.
Since exposures tend to be primarily occupational, no race, age or sex predilection exists worldwide.

Risk Factors for Brucellosis

 

• Consumption of infected meat products.
• Consumption of unpastuerized cheese/milk.
• Direct contact with infected animals.

 

Progression of Brucellosis

The acute brucellosis incubation period is 1-3 weeks. The onset is insidious, with malaise, headache, weakness, generalized myalgia and night sweats. The fever pattern is classically undulant, although continuous and intermittent patterns are also seen. Lymphadenopathy, hepatosplenomegaly and spinal tenderness may be present; arthritis, osteomyelitis, orchitis, epididymitis, meningoencephalitis and endocarditis have all been described.
Untreated brucellosis can give rise to chronic infection, lasting a year or more. This is characterized by easy fatiguability, myalgia, and occasional bouts of fever and depression. Splenomegaly is usually present. Occasionally infection can lead to localized brucellosis. Bones and joints, spleen, endocardium, lungs, urinary tract and nervous system may be involved. Systemic symptoms of brucellosis occur in less than one-third.

How is Brucellosis Diagnosed?

– Blood culture

• Urine culture (clean catch)
• Cerebrospinal Fluid culture
• Bone marrow culture
• Serology detecting brucellosis antigen

 

Prognosis of Brucellosis

Because of the predilection to affect joints and the vague symptoms and chronic nature of the brucellosis, the infection can result in relatively long-term disability. The longer it takes to diagnose the illness, the longer the patient is disabled which is why the causative bacterium is considered a biological agent. Having said this, nearly all patients respond to appropriate antibiotic therapy, with fewer than 10% relapsing after this type of brucellosis treatment.

How is Brucellosis Treated?

Brucellosis is treated with a combination of doxycycline 200 mg daily and rifampicin 600-900 mg daily for 6 weeks, but relapses occur. Alternatively, tetracycline can be combined with streptomycin, which is usually given for only the first 2 weeks of treatment. Prevention and control involve careful attention to hygiene when handling infected animals, eradication of infection in animals, and pasteurization of milk. No vaccine is available for use in humans.

Brucellosis References

[1] Australian National Notifiable Diseases.
[2] eMEDICINE.
[3] Hoover DL, Friedlander AM: Brucellosis. In: Textbook of Military Medicine: Medical Aspects of Chemical and Biological Warfare. 1997: 513-521.
[4] Kumar P, Clark M. CLINICAL MEDICINE. WB Saunders 2002 Pg 81.
[5] MEDLINE Plus.