Brucellosis

Alternative names: Cyprus fever; Gibraltar fever; Malta fever; Mediterranean fever; Rock fever; Undulant fever.

Brucellosis is an infection caused by contact with animals carrying Brucella bacteria.  It is most common among people who come into regular contact with animals or meat.  Although symptoms may initially be flu-like, brucellosis can persist for years.

Brucellosis appears to be an ancient disease, described at least 2,000 years ago by the Romans.

Incidence; Causes and Development

Although in decline in the U.S. due to widespread animal vaccination, brucellosis is a significant problem in several parts of the world.  In 2010 it was estimated to be causing around 500,000 infections worldwide per year, only 100-200 of which occurred in the U.S.

Brucellosis is caused by infection with the bacteria Brucella.  These bacteria are present in the reproductive organs various animals, for example cows, goats, pigs, or dogs, and are a significant cause of abortions and sterility in these animals.  These bacteria are excreted in host animals' fluids (urine, milk, placental fluid, etc.)  and it is this exposure to animal secretions that is the usual cause of brucellosis in humans.  Consumption of infected meat or unpasteurized dairy products can cause this disease in humans.

Signs and Symptoms

Infection may be acute, chronic (causing symptoms for years), or may be asymptomatic.

Fever is the most common symptom, occurring in 80-100% of cases and often rising/falling in waves, peaking in the afternoon.  Chills usually occur along with the fever.  Other symptoms that are present in most cases are loss of appetite, weight loss, fatigue, weakness, excessive sweating, and malaise.

Many patients (some 50-80%) also experience bone and joint symptoms including joint stiffness, inflammation (arthralgia) and pain, upper and lower back/spine pain, muscle pain, and swollen glands.

Headache and depression may occur in about half of all cases, as well as abdominal pain, constipation, diarrhea, and vomiting.

Further symptoms can include dizziness, instability while walking (unsteady gait), urinary retention, coughing, shortness of breath, and hearing loss.

About 5-10% of patients have skin-related symptoms such as nodules, abscesses, eruptions, scaly skin patches, lesions that resemble impetigo, psoriasis or eczema, rashes, red or purple patches caused by capillary hemorrhage, and eye involvement including cataracts.

Diagnosis and Tests

Confirmation of a brucellosis diagnosis involves blood work, bone marrow and urine cultures, and other techniques.  The liver and/or spleen may become enlarged.  Affected areas may become tender; bursitis and decreased range of motion may occur in joints.  Low muscle tone (hypotonia) or muscle tightness/stiffness and poor/absent reflexes (areflexia) or overactive reflexes (hyperreflexia) are also often present.

Treatment and Prevention

Prevention involves avoiding direct contact with infected animals and animal products.  Vaccination is not available for humans.

Complications

Possible complications include bone and joint lesions, encephalitis, infective endocarditis, meningitis.