What is Brucellosis?

Brucellosis is an infectious disease caused by a genus of small gram-negative bacteria known as Brucella. Initial symptoms are usually flu-like, but prolonged infections can lead to more serious effects.
Scanning electron micrograph of Brucella abortus bacteria (coccobacillus prokaryote), causes brucellosis, fever, mag. 3900x at 35mm. CPimages.ca/Phototake

This is a short videos form the Idaho National Lab introducing Brucellosis:

There are 10 species with the genus Brucella. Each species was originally classified according to its natural host preference. Modern genetic analysis has, for the most part, validated this classification. Seven of the species of Brucella are listed below along with their preferred host species. Out of 10 classified Brucella species, B. melitensis, B. abortus, B. suis, and B. canis are pathogenic to humans.
Brucella species.jpg
Descriptions of various species of Brucella and their preferred hosts.from: Principles and Practice of Clinical Bacteriology. 2006

Brucellosis can cause of range of signs and symptoms, some of which may present for prolonged periods of time.
Initial symptoms can include:
  • sweats
  • fever
  • malaise
  • anorexia
  • headache
  • pain in muscles, joint, and/or back
  • fatigue
Some signs and symptoms may persist for longer periods of time. Others may never go away or reoccur.
These can include:
  • recurrent fevers
  • arthritis
  • swelling of the testicle and scrotum area
  • swelling of the heart (endocarditis)
  • neurologic symptoms (in up to 5% of all cases)
  • chronic fatigue
  • depression
  • swelling of the liver and/or spleen

Brucellosis is more incapacitating than deadly. Mortality rate: < 2% of untreated cases and generally occurs as a result of endocarditis. Development of endocarditis may necessitate valve replacement. Single drug therapy is associated with a high relapse rate in adults; combination therapy is recommended.

Transmission (from CDC)
Humans are generally infected with brucellosis in one of three ways:

Eating undercooked meat or consuming unpasteurized/raw dairy products
Brucella Transmission.jpgThe 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 cause brucellosis (inhalation)
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 entering the body through skin wounds or mucous membranes
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
  • veterinarians
People who hunt animals may also be at risk. When they are in contact with infected animals, exposure to the bacteria may occur through:
  • skin wounds
  • accidentally ingesting undercooked meat
  • inhaling the bacteria while dressing their game. Commonly infected animals include: bison, elk, caribou, moose and wild hogs (feral swine).

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.

History of Brucellosis

Brucellosis has many alternate names referencing its history and location including "Bang's disease", "Malta fever", "rock fever", “undulant fever”, "Mediterranean fever", "Crimean fever", "Gibraltar fever", or "Maltese fever".

Brucellosis was first noticed by British medical officers during the Crimean War in Malta in 1850. By 1887, Dr, David Bruce first determined a relationship between the disease and the bacteria. The term Brucella / Brucellosis was named for Dr. Bruce.
Dr. David Bruce, man for which Brucella is named. http://en.wikipedia.org/wiki/David_Bruce_(microbiologist)

The term 'Crimean fever' is used for brucellosis because it was first noticed during the Crimean War (1853 - 1856).

By 1905, a Maltese doctor and archaeologist named Sir Themistocles Zammit was knighted for realizing that unpasteurized milk was a major source of the bacteria (the source of the terms 'Maltese Fever' and 'Malta Fever').
The terms 'rock fever' and 'Gibraltar fever' were utilized for brucellosis around this time because of the reference to the Rock of Gibraltar where it was prevelant.

By the 20th century, most of the 19th century terms for this infection were replaced with 'Mediterranean Fever'.

Role of Brucella in Bioterrorism

  • Brucella has traditionally been considered a biological weapon. It was the subject of extensive offensive research in the past, and still belongs to category B pathogens on most lists.
  • Several key characteristics of Brucella species make it more or less suitable for a biological weapon such as the availability of virulent strains, storage stability, and dissemination into the environment. Aerosol transmission and dissemination is considered to be the most effective means of delivery. In addition, Brucella can be easily cultured from infected animal or human materials. The transfer, storage and dissemination of the bacteria are also manageable. An intentional contamination of food with Brucella species could also pose a threat with low mortality rate.
  • In 1942, Brucella suis was first weaponized in the USA and formulated to maintain its long-term viability. It was placed into bombs and tested with animal targets in field trials between 1944 and 1945. However, the USA declared that the offensive Brucella program has been terminated, and all biological weapon munitions were destroyed in 1969. During of former the Soviet Union, Brucella was extensively formulated as one of the agents developed for offensive purposes.
  • Several biological and pathological properties of the Brucella species renders it to be an attractive pathogen that can be used as a potential agent in biological warfare. These bacteria are highly infectious through aerosol route with a dose of approximately 10-100 microorganisms. It has been estimated that release of 50 kg of B. suis from a plane along 2 km line and 10 km upwind on a city with 500.000 people would affect 125.000 people resulting in 500 deaths.
  • Using Brucella spp. as a biologic agent for bioterrorism through the food chain could be possible but bioterrorism-related cases may remain as localized clusters. This kind of intentional food contamination would be effective after industrial level since pasteurization kills the pathogen. Not many people are expected to be affected by this type of potential attack with intentional food contamination.

Bioterror warhead.jpg
Workers in protective suits hold dummy munition during a demonstration at a chemical weapons disposal facility in Muenster, Germany. source: npr.org

The best way to prevent brucellosis infection is to be sure you do not consume:
    • undercooked meat
    • unpasteurized dairy products, including: milk,cheese & ice cream
  • Pasteurization is when raw milk is heated to a high temperature for a short period of time. This heating process destroys harmful bacteria that may make the milk unsafe to consume.
  • If you are not sure that the dairy product is pasteurized, do not eat it.
  • People who handle animal tissues (such as hunters and animal herdsman) should protect themselves by using: Rubber gloves, gowns, & goggles.
  • In the event of a biological attack, the standard gas mask should adequately protect personnel from airborne brucellae, since the organisms are probably unable to penetrate intact skin. After personnel have been evacuated from the attack area, clothing, skin, and other surfaces can be decontaminated with standard disinfectants to minimize risk of infection by accidental ingestion, or by conjunctival inoculation of viable organisms.
An example of a gas mask that would be effective against a Brucella attack.
An example of a gas mask that would be effective against a Brucella attack.

Brucella as a Potential Agent of Bioterrorism. Dogany & Dogany. Recent Patents on Anti-Infective Drug Discovery, 2013, Vol. 8, No. 1

CDC. Brucellosis. 2012. Retrieved from: http://www.cdc.gov/brucellosis/index.html

Gillespie, S. and Hawkey, P. Principles and Practice of Clinical Bacteriology. John Wiley & Sons. 2006. pp 265-70.

Sharma, M.K. & Sharma, P.S. Brucellosis. Retrieved from: http://www.thelivercarefoundation.org/?page=bruc

Yongqun, H. Analyses of Brucella Pathogenesis, Host Immunity, and Vaccine Targets using Systems Biology and Bioinformatics. Cell Infect Microbiol. 2012; 2: 2.