Brucellosis

The disease brucellosis is the most important zoonotic disease worldwide. It affects both man and livestock. The etiological agents are gram-negative coccobacillae belonging to the genus Brucella. Brucella melitensis, B. abortus and B. suis have small ruminants, cattle and pigs respectively as their principle hosts.

Epidemiology of brucellosis
Epidemiology is complex. Different factors contribute to the prevalence and spread in livestock:

• the farming system and practices
• farm sanitation
• livestock movement
• mixing and trading of animals
• sharing of grazing grounds
• sharing of males for breeding
• contact with wildlife

Transmission from infected livestock to man
• Directly > through contact with infected animals or animal products
• Indirectly > through consumption of products, mainly raw milk and soft cheese prepared with unpasteurized milk

Brucella has a very low infecting level, making infection a genuine risk to those occupationally exposed to cattle, and to the public through the consumption of contaminated unprocessed dairy and meats.

Effects of brucellosis in infected animals 
• abortion
• reduced fertility
• weak offspring 
• reduced productivity

Effects of brucellosis in man
The disease may affect almost any organ and causes a variety of problems. If not treated early brucellosis may lead to severe and prolonged disability.

Impact
Brucellosis may have a deep economic and social impact. In particular pastoralists, who for their nutritional needs are often entirely dependent on their livestock, can be severely affected. Lack of resources and weak veterinary and medical services often hamper the control and management of this disease in these populations.

Prevention and control
Measures to control the spread and transmission of the pathogen:
• mass vaccination of livestock; this is a crucial measure that eventually will lead to a reduction of brucellosis in the human population
• restriction of trade and animal movement
• culling of infected animals
• improved farm sanitation
• pasteurization of milk (to reduce the risk of infection of the human population)

Treatment and diagnosis of human brucellosis
• Human brucellosis requires protractive treatment with a combination therapy.
• The diagnosis of brucellosis requires laboratory confirmation.

Culture is the gold standard, but culture facilities are rarely available in endemic areas and therefore one often resorts to serology. The Rose Bengal test may be used as a simple screening test and the serum agglutination test or ELISA are used for confirmation.