| BrucellosisDefinition - A bacterial zoonosis caused by strains of Brucella
- Transmitted directly or indirectly to humans from infected animals, predominantly domesticated ruminants and swine
- Known colloquially as undulant fever because of its remittent character
- Other names include Mediterranean fever and Malta fever.
 Epidemiology - Incidence
- Considered by the World Health Organization (WHO) to be the most widespread zoonosis in the world
- True incidence of human brucellosis is unknown.
- Reported incidence in endemic-disease areas varies widely, from < 0.01 case to > 200 cases per 100,000 population.
- An estimated 100–200 cases per year occur in the U.S.
- Most cases are reported from California, Florida, Texas, and Virginia.
- The occurrence of brucellosis is closely related to its prevalence in domesticated animals.
- Geographic distribution
- Worldwide, except for a few countries where disease has been eradicated from animal reservoirs
- Bovine brucellosis is the subject of control programs in many parts of the world.
- Eradicated from cattle populations of Australia, New Zealand, Bulgaria, Canada, Cyprus, Great Britain, Japan, Luxembourg, Romania, Scandinavia, Switzerland, and the Czech and Slovak Republics
- Incidence in cattle reduced to low level in the U.S. and most of Western Europe
- Efforts to eradicate from sheep and goat populations much less successful
- Major public health problem in Mediterranean countries, Asia, and parts of Africa and South and Central America
- Human brucellosis transmission
- Transmitted via occupational or domestic exposure to infected animals or their products
- Occupation as farmer, shepherd, goatherd, veterinarian, or worker in slaughterhouse or meat-processing plant in endemic area
- Consumption of dairy products, especially soft cheeses, unpasteurized milk, and ice cream
- Under exceptional circumstances: consumption of raw meat and bone marrow
- Rarely: contact with cosmetic products containing infected fetal materials
- Laboratory workers also at risk
- Person-to-person transmission and transfer by blood or tissue donation are extremely rare.
- Bioterrorism risk
Risk Factors - Occupational or domestic exposure to infected animals or their products
- Farmers
- Shepherds
- Goatherds
- Veterinarians
- Slaughterhouse or meat-processing workers in endemic areas
- Laboratory workers handling cultures or infected samples
- Family members (including children) of individuals involved in animal husbandry may be at risk.
- Difficult to differentiate food-borne infection from environmental contamination
- Travel to endemic areas
- Bioterrorism
Etiology - Caused by strains of Brucella, a genus with 4 major species
- B. melitensis: most common cause of disease in humans
- Main sources: sheep, goats, camels
- B. abortus
- Usually acquired from cattle or buffalo
- B. suis
- Acquired from swine, except for 1 variant in reindeer and caribou and another in rodents
- B. canis
- Characteristics of brucellae
- Small, gram-negative, unencapsulated, nonsporulating rods or coccobacilli
- Facultative intracellular parasites in vivo
- Resistant to freezing and drying
- Resistance to drying renders brucellae stable in aerosol form and facilitates airborne transmission.
- Brucellae survive for:
- Up to 2 months in soft cheeses made from goat or sheep milk
- At least 6 weeks in dry soil contaminated with infected urine, vaginal discharge, or placental or fetal tissues
- At least 6 months in damp soil or liquid manure kept under cool, dark conditions
- Brucellae are easily killed by:
- Boiling and pasteurization
- Common disinfectants used under optimal conditions (but likely to be much more resistant at low temperatures or in the presence of heavy organic contamination)
- Transmission
- Ingestion
- Inhalation
- Mucosal or percutaneous exposure
- Accidental injection of the live vaccine strains of B. abortus (19 and RB51) and B. melitensis (Rev 1) can cause disease.
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