Brucellosis is a bacterial infection that spreads from animals to people. Most commonly, people are infected by eating raw or unpasteurized dairy products. Sometimes, the bacteria that cause brucellosis can spread through the air or through direct contact with infected animals.
Signs and symptoms of brucellosis may include fever, joint pain and fatigue. The infection can usually be treated with antibiotics. However, treatment takes several weeks to months, and the infection can recur.
Brucellosis affects hundreds of thousands of people and animals worldwide. Avoiding raw dairy products and taking precautions when working with animals or in a laboratory can help prevent brucellosis.
Symptoms of brucellosis may show up anytime from a few days to a few months after you've been infected. Signs and symptoms are similar to those of the flu and include:
- Loss of appetite
- Joint, muscle and back pain
Brucellosis symptoms may disappear for weeks or months and then return. Some people have chronic brucellosis and experience symptoms for years, even after treatment. Long-term signs and symptoms may include:
- Recurrent fevers
- Inflammation of the inner lining of the heart chambers (endocarditis)
- Joint inflammation (arthritis)
- Arthritis of the spinal bones (spondylitis)
- Arthritis of joints where the spine and pelvis connect (sacroiliitis)
When to see a doctor
Brucellosis can be hard to identify, especially in the early stages, when it often resembles other conditions, such as the flu. See your doctor if you develop a rapidly rising fever, muscle aches or unusual weakness and have any risk factors for the disease, or if you have a persistent fever.
Brucellosis affects many wild and domestic animals, including:
- Pigs and wild hogs
- Dogs, especially those used in hunting
A form of brucellosis also affects harbor seals, porpoises and certain whales.
The most common ways that bacteria spread from animals to people are by:
- Eating raw dairy products. Brucella bacteria in the milk of infected animals can spread to humans in unpasteurized milk, ice cream, butter and cheeses. The bacteria can also be transmitted in raw or undercooked meat of infected animals.
- Inhaling contaminated air. Brucella bacteria spread easily in the air. Farmers, hunters, laboratory technicians and slaughterhouse workers can inhale the bacteria.
- Touching blood and body fluids of infected animals. Bacteria in the blood, semen or placenta of an infected animal can enter your bloodstream through a cut or other wound. Because normal contact with animals — touching, brushing or playing — doesn't cause infection, people rarely get brucellosis from their pets. Even so, people who have weakened immune systems should avoid handling dogs that are known to have the disease.
Brucellosis normally doesn't spread from person to person, but in a few cases, women have passed the disease to their children during birth or through their breast milk. Rarely, brucellosis may spread through sexual activity or through contaminated blood or bone marrow transfusions.
While brucellosis is rare in the United States, it is more common in other parts of the world, especially:
- Southern Europe, including Portugal, Spain, Turkey, Italy, Greece, Southern France
- Eastern Europe
- Mexico, South and Central America
- The Caribbean
- The Middle East
Occupations at higher risk
People who work with animals or who come into contact with infected blood are at higher risk of brucellosis. Examples include:
- Dairy farmers
- Slaughterhouse workers
Brucellosis can affect almost any part of your body, including your reproductive system, liver, heart and central nervous system. Chronic brucellosis may cause complications in just one organ or throughout your body. Possible complications include:
- Inflammation of the inner lining of the heart chambers (endocarditis). This is one of the most serious complications of brucellosis. Untreated endocarditis can damage or destroy the heart valves and is the leading cause of brucellosis-related deaths.
- Arthritis. Joint inflammation is marked by pain, stiffness and swelling in the joints, especially the knees, hips, ankles, wrists and spine. Inflammation of the joints in your spine (spondylitis) or the joints linking the lower spine and pelvis (sacroiliitis) can be particularly hard to treat and may cause lasting damage.
- Inflammation and infection of the testicles (epididymo-orchitis). The bacteria that cause brucellosis can infect the epididymis, the coiled tube that connects the vas deferens and the testicle. From there, the infection may spread to the testicle itself, causing swelling and pain, which may be severe.
- Inflammation and infection of the spleen and liver. Brucellosis can also affect the spleen and liver, causing them to enlarge beyond their usual size.
- Central nervous system infections. These include potentially life-threatening illnesses such as inflammation of the membranes surrounding the brain and spinal cord (meningitis) or inflammation of the brain itself (encephalitis).
To reduce the risk of getting brucellosis, take these precautions:
- Avoid unpasteurized dairy foods. In recent years in the United States, few cases of brucellosis have been linked to raw dairy products from domestic herds. Still, it's best to avoid unpasteurized milk, cheese and ice cream, no matter what their origin. If you're traveling to other countries, avoid all raw dairy foods.
- Cook meat thoroughly. Cook a whole cut of meat until it reaches an internal temperature of 145 F (63 C) and let it rest for at least three minutes — a medium doneness. Cook ground meat to 160 F (71 C) — well done. Cook all poultry, including ground poultry, to 165 F (74 C). When traveling outside of the United States, avoid undercooked meats.
- Wear gloves. If you're a veterinarian, farmer, hunter or slaughterhouse worker, wear rubber gloves when handling sick or dead animals or animal tissue or when assisting an animal giving birth.
- Take safety precautions in high-risk workplaces. If you work in a laboratory, handle all specimens under appropriate biosafety conditions. Slaughterhouses should also follow protective measures, such as separating the killing floor from other processing areas and use of protective clothing.
- Vaccinate domestic animals. In the United States, an aggressive vaccination program has nearly eliminated brucellosis in livestock herds. Because the brucellosis vaccine is live, it can cause disease in people. Anyone who has an accidental needle stick while vaccinating an animal should be treated.
Doctors usually confirm a diagnosis of brucellosis by testing blood or bone marrow for the brucella bacteria or by testing blood for antibodies to the bacteria. To help detect complications of brucellosis, your doctor may order additional tests, including:
- X-rays. X-rays can reveal changes in your bones and joints.
- Computerized tomography (CT) scan or magnetic resonance imaging (MRI). These imaging tests help identify inflammation or abscesses in the brain or other tissues.
- Cerebrospinal fluid culture. This checks a small sample of the fluid that surrounds your brain and spinal cord for infections such as meningitis and encephalitis.
- Echocardiography. This test uses sound waves to create images of your heart to check for signs of infection or damage to your heart.
Treatment for brucellosis aims to relieve symptoms, prevent a relapse of the disease and avoid complications. You'll need to take antibiotics for at least six weeks, and your symptoms may not go away completely for several months. The disease may also return and become chronic.
Preparing for an appointment
If you think you may have brucellosis, you're likely to start by seeing your family doctor or a general practitioner. You may be referred to an infectious disease specialist.
A diagnosis of brucellosis depends on understanding whether, how and when you were exposed to the bacteria that cause the disease. You can help your doctor by being prepared with as much information as possible.
What you can do
Before your appointment, you may want to write a list of answers to the following questions:
- When did you first begin experiencing symptoms?
- Have you eaten any raw (unpasteurized) dairy products, such as milk or goat cheese?
- Does your job involve contact with animals or with animal tissues?
- Have you traveled to countries other than the United States during the past year?
- Do you work in a lab where infectious organisms are present?
- Have you gone hunting recently?
What to expect from your doctor
During the physical exam, your doctor may:
- Ask you to move your joints, to check for pain and stiffness
- Check your reflexes and the strength of your muscles
- Press on your abdomen to determine if organs are enlarged or tender
Content Last Updated: September 25, 2021