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Brucellosis
What causes brucellosis?
- Bacteria from the Brucella genus (see picture below)
- Most commonly, infections in humans are caused by B. abortus,
B. melitensis, B. suis, and rarely B. canis
- Brucellosis is a zoonotic
disease; it can be a significant human public health concern,
especially if caused by B. melitensis
- In humans, brucellosis can also be called undulant fever (undulant
means rising and falling in waves)
A magnified picture of Brucella melitensis bacteria
(from the CDC’s Public Health Image Library)
What animals can spread brucellosis to humans?
- Cattle can spread B. abortus
- Sheep and goats can spread B. melitensis (this disease is typically
not present in the US)
- Pigs (and also cattle and reindeer) can spread B. suis
- Dogs can spread B. canis
How do the animals get infected?
- By direct contact with infected animals, blood, tissues, urine,
vaginal discharges, and aborted fetuses from other (infected)
animals
- The bacteria spread in the air to animals in pens and stables
(rare)
How do humans typically get brucellosis?
There are several ways that humans can become infected.
- Most transmission is by drinking or eating unpasteurized (raw)
milk or cheese or other dairy products
- By contamination of cuts or scrapes in the skin with the bacteria
(through handling infected animals, animals parts, of infected
aborted fetuses)
- Rarely, by breathing in the bacteria (for example, from dried
animal urine that has been kicked up into the air)
- Breastfed babies can become infected from their mother’s
milk, if the mother is infected
- Also, humans can become infected if they receive a contaminated
tissue transplantation
What are the symptoms of brucellosis in humans?
- The onset of disease may be acute (rapid) or prolonged
- The acute form happens during the first 8 weeks; symptoms are
generally flu-like (fever, sweats, headache, tiredness, lack of
appetite, and back pain)
- The prolonged phase can last for months; symptoms include recurrent
fevers, arthritis, and severe weakness
- There is also a chronic form (infection for more than one year);
symptoms include chronic fatigue, depressive episodes, and arthritis
- People rarely die from brucellosis; however, the disease can
be very serious and cause long-term disability
Who is most at risk for brucellosis?
- Persons who eat or drink unpasteurized (raw) dairy products,
such as milk and cheese
- Hunters, veterinarians, and persons working in meat slaughterhouses;
laboratory workers may be at risk for inhaling Brucella organisms
- In general, infections are rare in the US
- Most cases are reported from California, Florida, Texas, and
Virginia; the California cases are frequently associated with
eating unpasteurized cheese imported from Mexico
How can brucellosis be prevented?
- Avoid eating unpasteurized milk, cheese, ice cream, or other
dairy products, especially when traveling
- Hunters should use rubber gloves when field dressing animals
- There is no vaccine available for humans
- A vaccine is available for animals; however, since 1934 the
United States Department of Agriculture (USDA) has been very active
in eradicating brucellosis from animals. As of April 2003, 48
states were considered brucellosis-free, including Maryland.
Additional information
Pet dogs that become infected with B. canis can (rarely) transmit
the disease to humans; however, most dog infections do not result
in human illness. Immunocompromised individuals (people with weakened
immune systems, such as cancer patients and HIV-infected individuals)
should avoid handling infected dogs, as they may be at increased
risk for infection.
Links
CDC
website on brucellosis
Brucellosis
in animals
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