Last Reviewed: December 2017

What is brucellosis?

Brucellosis is a bacterial disease caused by the Brucella bacteria. Brucella usually infects animals but can spread to humans. Animal species most commonly infected with brucellosis include sheep, cattle, goats, pigs, camels, and dogs. In humans, it can cause symptoms of fever, headache, and fatigue among others. Brucellosis in humans is not very common in the United States with fewer than 150 cases reported every year.

Who gets brucellosis?

Everyone is capable of getting brucellosis if exposed to the Brucella bacteria. People become infected by coming into contact with animals or animal products that are contaminated with these bacteria. Illness is more likely to occur in people who may handle infected animals including slaughterhouse workers, meat-packing employees, veterinarians, and people who drink unpasteurized (raw) milk or eat unpasteurized cheeses, especially those produced in high risk regions of the world. High risk regions include the Mediterranean Basin, South and Central America, Eastern Europe, Asia, Africa, and the Middle East. In the United States, brucellosis can also occur in people who hunt, handle, or are in contact with wild (feral) pigs or who are exposed to the bacteria in a laboratory. Very rarely, human infections have occurred from consumption of raw (unpasteurized) milk from cows in the U.S. that have been vaccinated with the RB51 strain.

How is brucellosis spread?

The most common way of getting brucellosis is by eating or drinking unpasteurized (raw) dairy products (milk and cheese) since animals pass the bacteria in their milk. People can also become infected by breathing in the bacteria or by the bacteria entering the body through skin wounds or mucous membranes. Discharges (blood, fluid, other excretions) from cattle, goats, swine, and dogs that abort their fetus when they have infection can spread brucellosis to handlers. It is unlikely that brucellosis would spread from person to person. However, infected mothers have spread the infection to their infants through breast milk.

What are the symptoms of brucellosis and when do they appear?

The initial symptoms of brucellosis include irregular fever of variable duration, headache, weakness, profuse sweating, chills, weight loss and generalized aching. Brucellosis can also cause long-lasting or chronic symptoms such as recurrent fevers, joint pain, testicular swelling, heart infections, nervous system impairment, depression, and fatigue. Death from brucellosis is rare.

Symptoms usually appear within 2 to 4 weeks after exposure, but can begin any time between 5 days and 6 months after exposure.

How is brucellosis diagnosed?

Brucellosis is diagnosed in a laboratory using tests on blood or other body tissue that indicate infection with the bacteria.

What is the treatment for brucellosis?

Brucellosis is treated with antibiotics. Generally, rifampin and doxycycline are recommended in combination for treatment. Early diagnosis leading to quick treatment is important to prevent chronic infection.

Does past infection with brucellosis make a person immune?

It is unlikely that an individual will be reinfected. However, if not properly treated, the disease may last for more than a year.

What can be done to prevent the spread of brucellosis?

The use of pasteurized milk and cheeses and prevention of contact with infected cattle, sheep, goats, and swine will reduce the risk of infection. In addition, those who are involved in the slaughter and butchering of livestock and other animals should wear rubber gloves when coming into contact with the blood and guts of animals.

I am a veterinarian, and I was recently exposed to the animal vaccine strain RB51 while I was vaccinating cattle. What do I need to do?

B. abortus RB51 is a strain of this Brucella developed specifically for vaccinating cattle against brucellosis. Accidental human exposure to RB51, though uncommon, has resulted in development of symptoms consistent with brucellosis. Exposures have included needle sticks, eye and wound splashes, and contact with infected material. Other vaccines, such as B. abortus S19 for cattle and B. melitensis Rev-1 for sheep and goats, can also cause infection in humans. If you are exposed to any of these vaccines you should see a health care provider and call your local health department. Depending on the nature of the exposure, post-exposure prophylaxis with antibiotics may be recommended. Although extremely rare, human infection can also occur from consumption of raw (unpasteurized) milk from vaccinated cows. RB51 infection can only be diagnosed through blood culture.

What is the risk to pregnant women?

Women who are pregnant and have beenexposed to Brucella should consult with their obstetricians/healthcare provider for evaluation. Prompt diagnosis and treatment of brucellosis in pregnant women can prevent complications including miscarriage.