Brucellosis

Background

Brucellosis is an infection caused by bacteria of the genus Brucella. These bacteria primarily cause disease among animals, such as sheep, pigs, cattle, goats, and dogs. Humans can become infected by:

• Eating or drinking contaminated food, particularly unpasteurised milk and cheese.
• Direct contact with an infected animal. The organisms can enter humans through an open skin wound, mucous membrane, or conjunctiva.
• Inhaling the organism; this route is a particular problem for laboratory workers or those who work with animals or animal carcasses.

Person-to-person spread is extremely rare.

Brucellosis is now rare in developed countries due to pasteurisation of milk and milk products, and disease control amongst animals. Around 100-200 cases occur per year in the United States. Worldwide areas listed as high risk are the Mediterranean Basin, South and Central America, Eastern Europe, Asia, Africa, the Caribbean, and the Middle East.

Clinical features

The incubation period of brucellosis is generally 1-8 weeks. Symptoms are variable and non-specific.

• Brucellosis can be an acute illness (abrupt onset, short duration) or symptoms may be chronic (long-lasting).
• Most patients have ‘flu-like symptoms, such as fever, malaise, loss of appetite, muscle aches, sweats, and joint aches.
• The infection may spread to the central nervous system causing depression, headache, and irritability or, in advanced cases, meningoencephalitis.
• The infection may also spread to the inner lining of the heart and heart valves; this is called endocarditis and occurs in approximately 2% of patients.
• Other complications include epididymo-orchitis (inflammation of the epididymis and/or testis), granulomatous hepatitis (clumps of inflammatory cells in the liver), and arthritis.
• Death from brucellosis is rare, and usually results from meningoencephalitis or endocarditis.

Skin manifestations

Skin complications generally affect less than 5% of patients with systemic brucellosis. A variety of skin lesions have been documented. These include:

• Widespread red-purple papulonodular lesions (small bumps)
• Erythema nodosum
• Widespread maculopapular rash (red-purple flat or slightly raised spots)
• Extensive purpura.

Contact with animals with brucellosis may also result in:

• Contact urticaria – Itch and redness of the upper limbs (and sometimes face) within a few hours of exposure in veterinarians and animal handlers. This resolves in about 2 weeks and may be due to an allergic reaction.
• Chronic ulceration and multiple abscesses in the skin and subcutaneous tissues in patients with high occupational exposure risk.

Diagnosis

Brucellosis can be diagnosed by detecting Brucella organisms in samples of blood or bone marrow. Blood tests can also reveal antibodies against the bacteria.

Treatment

Brucellosis is treated with antibiotics. Usually a combination of doxycycline and rifampicin are given for 6 weeks. Relapse of infection occurs in up to 10% of patients, even with appropriate treatment.

Prevention

• No human vaccine is available, but immunisation of animals reduces human exposure to the disease
• Avoid unpasteurised milk, cheese, or ice-cream, particularly when travelling to endemic areas
• Protective clothing should be worn by people who work with animals and animal carcasses