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Larry M. Bush

, MD, FACP, Charles E. Schmidt College of Medicine, Florida Atlantic University

Last full review/revision Feb 2020| Content last modified Feb 2020
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Brucellosis is an infection caused by several species of the gram-negative bacteria Brucella and characterized by fever and bodywide symptoms.

  • Brucellosis is acquired mainly by having contact with infected animals or by consuming unpasteurized contaminated milk or other dairy products or undercooked contaminated meat.

  • People typically have a fever, chills, a severe headache, low back pain, bone and joint pain, and other bodywide symptoms.

  • Most people recover in 2 to 3 weeks, even without treatment.

  • Doctors base the diagnosis on results of blood tests and cultures.

  • Two antibiotics are given at the same time to increase the chance of a cure.

(See also Overview of Bacteria.)

Brucellosis is rare in the United States, Canada, and Europe but is more common in the Middle East, the Mediterranean, Mexico, and Central and South America.

Brucellosis is acquired mainly by

  • Having direct contact with infected farm animals

  • Consuming unpasteurized contaminated milk or other dairy products or undercooked contaminated meat

People can also acquire brucellosis if they have contact with infected dogs, deer, moose, buffalo, or other animals or if they inhale airborne particles containing the bacteria. Brucellosis is rarely spread from person to person.

People at increased risk of getting brucellosis include laboratory workers and people who may handle infected animals or animal tissue, including meat packers, veterinarians, farmers, and livestock producers.

Inhaling only a few of the bacteria can cause infection. Thus, the bacteria could be used in biological warfare.


Symptoms of brucellosis can begin 5 days to several months after people are exposed to Brucella bacteria.

People typically have

  • A fever, which may return repeatedly for months and sometimes years

Symptoms may begin suddenly with chills, night sweats, a severe headache, low back pain, bone and joint pain, and sometimes diarrhea. Or symptoms may begin gradually, with a feeling of being slightly ill, muscle pain, headache, and pain in the back of the neck.

The fever may come and go for several weeks.

Later symptoms include loss of appetite, weight loss, severe constipation, abdominal pain, joint pain, difficulty sleeping, weakness, irritability, and depression.

Sometimes infection develops in the brain, tissues that cover the brain and spinal cord (meninges), back bones (vertebrae), long bones (such as the thighbone), joints, heart valves, or other organs.

If people do not develop infections in these organs and tissues, they usually recover in 2 to 3 weeks, even without treatment. However, in some, the infection persists. About 5% of people with brucellosis die, usually when the brain, meninges, or heart valves are infected.


  • Blood tests and culture of blood or other tissues to check for the bacteria

Doctors take a sample of blood and send it to a laboratory to grow (culture) and identify the bacteria. Samples of bone marrow, obtained by aspiration, and cerebrospinal fluid (the fluid that surrounds the brain and spinal cord), obtained by spinal tap, may also be cultured.

Doctors may use the polymerase chain reaction (PCR) technique, so that the bacteria can be detected more quickly. The PCR technique increases the amount of the bacteria's DNA in blood or other tissues.

Usually, doctors also measure antibodies to the bacteria in blood.


The best way to prevent brucellosis is to avoid eating undercooked meat and unpasteurized dairy products. Pasteurization involves heating raw milk to a high temperature for a short period of time. This process destroys harmful bacteria that may be present in milk.

People who handle animals or animal tissue that may be infected should take precautions, such as wearing goggles and rubber gloves.

Vaccination of domestic animals (cattle, sheep, and goats) helps control the disease. There is no vaccine for people.


  • Two antibiotics given at the same time

Doctors give two antibiotics at the same time to increase the chance of a cure. Usually, one of the antibiotics is doxycycline, given by mouth. The second antibiotic can be either streptomycin or gentamicin, injected daily, or rifampin or ciprofloxacin, given by mouth. Children may be given the combination drug trimethoprim/sulfamethoxazole (TMP/SMX) plus rifampin.

After being treated, some people develop symptoms again. So people are periodically examined and tested for a year after treatment.

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