What is Brucellosis

Also known as undulant fever and Malta fever, brucellosis is a zoonotic (acquired from animals) infection caused by several species of the bacterium, Brucella.

It has a worldwide distribution, with the majority of cases in the United States reported in California, Iowa, Virginia and Texas. This reflects the cattle and dairy industries and other animal husbandry that are central to the economies of those states. There are 50 to 100 cases seen each year in this country.

The countries with the highest incidence of both animal and human brucellosis are those in the Middle East, the Mediterranean, Latin America and parts of Mexico.

The Brucella species are named for their primary hosts:

Brucella melitensis is found mostly is goats, sheep and camels, B. abortus is a pathogen of cattle, B. suis is found primarily in swine and B. canis is found in dogs.

There are two common ways people get infected with brucellosis. First are individuals that work with infected animals that have not been vaccinated against brucellosis. This would include farmers, slaughterhouse workers and veterinarians.

They get infected through direct contact or aerosols produced by the infected animal tissue.
B. abortus and B. suis are most common.

The second way is through ingesting unpasteurized dairy products. This is seen in people who travel to areas of the Middle East or Latin America (B. melitensis) where brucellosis is endemic in ovine ad bovine animals. "When in Rome" is an attitude many foreign travelers take to experience aspects of a foreign culture.

There have been several cases of domestically acquired brucellosis from people who have eaten Mexican cheese made from unpasteurized goat milk.

In the U.S., brucellosis has decreased over the decades due to vaccination of young animals and the slaughter of the sick ones.

Brucellosis is also an occupational hazard to laboratory workers who inappropriately handle specimens or have an accident or spill. Brucella is highly infectious in the aerosolized form.

If someone gets infected with Brucella, the incubation period is about 2-3 weeks, though it could be months. Fever, night sweats, severe headache and body aches and other non-specific symptoms may occur.

Acute and chronic brucellosis can lead to complications in multiple organ systems. The skeletal, central nervous system, respiratory tract, the liver, heart, gastrointestinal and genitourinary tracts can all be affected. Untreated brucellosis has a fatality rate of 5%.

Brucellosis can be diagnosed both serologically and through growing the organism in culture. The best specimens from culturing Brucella are blood and bone marrow. Other sample that may be sources of Brucella are spleen, liver, other sterile body fluids and abcesses. PCR assays are also available.

Treatment of brucellosis usually requires prolonged antibiotic therapy.

The Brucella bacterium is also a concern as a possible agent in a bioterrorism attack. It has a low infective dose (10-100 organisms) if acquired through inhalation.