Brucellosis is an infectious disease that causes flu-like symptoms, and it can spread from animals to humans. Without treatment, brucellosis can lead to serious complications.
Brucellosis occurs due to infection with Brucella bacteria.
People can develop it from contact with infected animals or from consuming uncooked or undercooked meat or unpasteurized dairy products. Brucellosis is uncommon in the United States.
This article describes in more detail the causes, symptoms, and treatments of brucellosis and provides some tips on prevention.
Brucellosis is an infectious disease caused by one of several species of bacteria from the Brucella genus.
It is a zoonotic illness, meaning that it can spread from animals to humans.
Different animal species host different types of Brucella bacteria. Not all can infect humans, and some are rare in the U.S.
The table below shows which animals carry different species of Brucella bacteria and the chances of encountering these bacteria in the U.S.
|Brucella melitensis||goats and sheep||not currently found in the U.S.|
|Brucella suis||swine||found in wild hogs in the U.S.|
|Brucella abortus||cattle||found in some cows, wild elk, and bison in the U.S.|
|Brucella canis||dogs||uncommon in the U.S.|
|Brucella ceti and pinnipediae||marine mammals||rarely infects people|
Brucella bacteria can enter the body through the eyes, mouth, or cuts in the skin. People can develop the infection in the following ways:
- Consuming uncooked meat: A person can also contract it by eating undercooked meat from an animal with the infection.
- Consuming unpasteurized dairy products: Brucella bacteria can live in the milk of cows, goats, and sheep. Raw milk and products made with it can pass on the infection.
- Having contact with infected animals: Breathing in Brucella bacteria or coming into contact with bodily fluid from an animal with the infection can spread it to humans.
Though it is rare, person-to-person transmission is possible, and it may occur through:
The symptoms of brucellosis may develop over days, weeks, or months. The specific symptoms depend partly on the organs and tissues affected.
Acute, subacute, and chronic infections
Around 50% of people with the infection develop acute brucellosis, in which case the symptoms begin within 1–2 days.
In a person with subacute brucellosis, the symptoms take weeks to develop.
When the disease is chronic, the symptoms last longer than 1 year, with repeated episodes of fever.
The initial symptoms of brucellosis are similar to those of the flu. They can include:
- a fever
- excessive sweating
- joint pain
- muscle aches and weakness
- a cough
- a headache
- appetite loss
- weight loss
- and less often:
- swollen lymph nodes
- spleen enlargement
- liver enlargement
Widespread vs. localized
The infection and resulting disease may be confined to one area, in which case, it is called localized brucellosis. If it affects multiple areas, a doctor may refer to the infection as widespread.
Below, find additional effects of brucellosis on specific parts of the body. We have organized the list with areas most likely to be affected at the top.
Localized brucellosis often causes inflammation of the bones at the bottom of the spine. This could lead to lower back pain and reduced mobility.
Brucellosis can cause abscesses to form on the liver, leading to a yellowing of the skin and the whites of the eyes, which are symptoms of jaundice.
A Brucella infection of the gastrointestinal tract can cause:
- abdominal pain
- weight loss
A Brucella infection of the urinary tract can cause inflammation of the kidneys. This could lead to severe pain below the ribcage.
A person might also experience painful inflammation of the testes and prostate.
Central nervous system
Brucellosis can sometimes cause inflammation of the brain, its surrounding membranes, and the spinal cord. This could lead to a stroke.
- a fever or chills
- night sweats
- difficulty breathing during physical activity
- shortness of breath while lying down
- a cough
- swelling of the feet, legs, or abdomen
Rarely, brucellosis can cause skin lesions, such as:
The doctor will consider the person’s medical history and symptoms and perform a physical examination.
They may then request a blood test called a serum agglutination test. This looks for antibodies that the immune system has developed to fight off Brucella bacteria. Having large numbers of these antibodies can be evidence of the infection.
A doctor may, in some cases, also need to take a sample of bone marrow for testing.
A doctor typically prescribes a combination of the antibiotics doxycycline and rifampin. The treatment usually lasts 6–8 weeks.
They may instead prescribe other combinations, such as doxycycline and streptomycin or trimethoprim and sulfamethoxazole.
A person should also get plenty of rest, which supports recovery.
In fewer than 10% of people who receive antibiotic treatment for the disease, symptoms of brucellosis reappear.
Some complications of brucellosis include:
- kidney damage
- liver damage
- problems with blood clotting
- blood poisoning
- encephalitis, inflammation of the brain
- a stroke
Certain activities increase the risk of coming into contact with the bacteria and developing brucellosis, including:
Brucellosis is more common in:
- South and Central America
- the Caribbean
- Eastern Europe
- the Mediterranean
- the Middle East
When visiting these places, avoid consuming raw milk and unpasteurized dairy. Also, wash the hands regularly with soap and clean water.
The following people may have a higher risk of coming into contact with Brucella bacteria:
- slaughterhouse workers
- meat-packing workers
- laboratory workers
Workplaces should have clear guidelines on reducing the risk of infection. In general, wear protective clothing, including a plastic gown, rubber gloves, and a facial covering.
People who hunt wild animals have a higher risk of developing brucellosis because they are more likely to come into contact with the bodily fluids of animals carrying the bacteria. Examples of these animals include:
- wild hogs
People who hunt can reduce their risk of brucellosis by:
- avoiding contact with dead or ill wild animals
- wearing eye protection and latex gloves when handling a carcass
- not feeding dogs raw meat from a carcass
- washing their hands thoroughly after hunting
- cleaning hunting and butchering tools with a disinfectant
There are strict measures in place to prevent and control brucellosis in farm animals. These include:
- buying new animals from healthy flocks or herds
- quarantining new animals
- testing meat and milk for Brucella bacteria
- vaccinating animals
- practicing good hygiene and animal husbandry
As of August 2020, all U.S. states are free from cattle and swine brucellosis.
Brucella bacteria are uncommon in dogs in the U.S. and Canada. However, the international trade in pets means that the risk of infection is still present.
Brucellosis can be difficult to diagnose in dogs and there is no standard veterinary treatment. Some dogs recover on their own and the bacteria pass from their systems.
Testing and good hygiene practices in kennels can help reduce the risk of brucellosis in dogs.
See a doctor if flu-like symptoms develop after any of the following:
- coming into contact with wild animals
- traveling abroad
- drinking unpasteurized milk or consuming unpasteurized dairy
- eating undercooked meat
Anyone with symptoms of brucellosis complications should also receive professional care.
Brucellosis is an infectious disease that can pass from animals to humans. The Brucella bacteria responsible can spread to people through contact with infected animals, the consumption of undercooked meat, or the consumption of unpasteurized dairy products.
Brucellosis is rare in the U.S., but anyone with symptoms should see a doctor. Without antibiotic treatment, brucellosis can cause serious complications.