Brucellosis is an infectious disease caused by bacteria. The isolation and identification of Brucella can confirm a diagnosis of brucellosis. Brucella is most commonly isolated from blood cultures.
Other names for brucellosis include (human disease/animal disease):
- Malta fever/Bang’s disease
- Undulant fever/enzootic abortion
- Mediterranean fever/epizootic abortion
- Rock fever of Gibraltar/slinking of calves
- Gastric fever/ram epididymitis
Humans are generally infected with brucellosis in one of three ways.
The most common way to be infected is by eating or drinking unpasteurized/raw dairy products. When sheep, goats, cows, or camels are infected, their milk becomes contaminated with the bacteria.
If the milk from infected animals is not pasteurized, the infection will be transmitted to people who consume the milk and/or cheese products.
Breathing in the bacteria that causes brucellosis may also lead to infection. This risk is generally greater for people in laboratories that work with the bacteria.
In addition, slaughterhouse and meat-packing employees have also been known to be exposed to the bacteria and ultimately become infected.
Bacteria can also enter wounds in the skin/mucous membranes through contact with infected animals.
This poses a problem for workers who have close contact with animals or animal excretions (newborn animals, fetuses, and excretions that may result from birth). Such workers may include: slaughterhouse workers, meat-packing plant employees and veterinarians.
Person-to-person spread of brucellosis is extremely rare. Infected mothers who are breast-feeding may transmit the infection to their infants. Sexual transmission has been rarely reported. While uncommon, transmission may also occur via tissue transplantation or blood transfusions.
Brucellosis can cause of range of signs and symptoms, some of which may present for prolonged periods of time.The gastrointestinal tract is affected in about 70% of cases. The skeletal system is affected in 20-60% of cases. Initial symptoms can include:
Some signs and symptoms may persist for longer periods of time. Others may never go away or reoccur. These can include:
- recurrent fevers
- swelling of the testicle and scrotum area
- swelling of the heart (endocarditis)
- neurologic symptoms (in up to 5% of all cases)
- chronic fatigue
- swelling of the liver and/or spleen
Before treatment begins, a diagnosis of brucellosis infection must be made by a doctor.
Tests will be performed to look for bacteria in samples of blood, bone marrow, or other body fluids. In addition, a blood test can be performed to detect antibodies against the bacteria.
Once a diagnosis is made, a doctor can prescribe antibiotics.
Depending on the timing of treatment and severity of illness, recovery may take a few weeks to several months. Death from brucellosis is rare, occurring in no more than 2% of all cases.
Unpasteurized cheeses (sometimes called “village cheeses”) from areas at increased risk for brucellosis may represent a particular risk for tourists.
Developing countries often do not have safeguards that can help prevent or monitor possible outbreaks, such as pasteurization laws, animal control/slaughter regulations, and brucellosis surveillance programs.
When traveling in these areas, some people may unknowingly consume unpasteurized dairy products. People from the U.S. who travel to these areas should:
- recognize that milk and dairy products may not be pasteurized and could be unsafe to consume.
- only consume meat products which are thoroughly cooked, since many countries cannot ensure brucellosis-free meat products.
People who hunt animals may also be at risk. When they are in contact with infected animals, exposure to the bacteria may occur. Some game animals that can transmit brucellosis include:
- wild hogs (feral swine)
Women who are pregnant and have been exposed to brucellosis should consult with their obstetricians/healthcare provider for evaluation. Laboratory tests and a short course of antibiotics also known as post-exposure prophylaxis (PEP) may be recommended.
Prompt diagnosis and treatment of brucellosis during pregnancy can be lifesaving for the fetus.
While rare, human-to-human transmission from lactating mothers to their breastfed infants has been reported.
If you have been diagnosed with brucellosis, please consult with your obstetrician/healthcare provider for healthy nursing options.
For More Information:
Seyed Mohammad Alavi, et al. Treatment of brucellosis: a systematic review of studies in recent twenty years Caspian J Intern Med. 2013 Spring; 4(2): 636–641
Dean AS, Crump L, Greter H, Hattendorf J, Schelling E, Zinsstag J (2012) Clinical Manifestations of Human Brucellosis: A Systematic Review and Meta-Analysis. PLoS Negl Trop Dis 6(12): e1929. doi:10.1371/journal.pntd.0001929
Brucella genomes and related information at PATRIC, a Bioinformatics Resource Center
Maley MW, Kociuba K, Chan RC (2006). “Prevention of laboratory-acquired brucellosis: significant side effects of prophylaxis“. Clin. Infect. Dis. 42 (3): 433–4. doi:10.1086/499112
Image: CDC Public Health Image Library (PHIL). Photomicrograph of the bacterium Brucella melitensis