- B. abortus occasionally in arthritis of cattle
- Isolated from closed cases of Poll Evil and Fistulous Withers
Overview
- Important zoonoses worldwide
- Cause chronic granulomatous diseases
- 6 species
- Target reproductive organs of certain species
- Infected animals act as reservoir of infection
- Organisms can remain viable in moist environment for months
- Cause undulant fever in humans
Characteristics
- Small, non-moltile, Gram negative coccobacilli
- Facultatice intracellular pathogens
- Modified Ziehl-Neelsen positive - clusters of red coccobacilli on smears
- Aerobic and capnophilic
- Catalase positive; oxidase and urease positive except for Brucella ovis
- Some species require enriched media for growth
- Non-haemolytic
- Smooth colonies of B. abortus, B. melitensis and B. suis are small, glistening, blue and translucent after incubation for 3-5 days, and become opaque with age
- Rough colonies of B. ovis and B. canis are dull, yellow, opaque and friable
- Slide agglutination with speicific antisera detect important antigens
- B. abortus lysed by specific bacterophages
- Oxidative metaboloic rates can differentiate species
Pathogenesis and pathogenicity
- Penetrate nasal, oral or pharyngeal mucosa
- Phagocytosed and carried to regional lymph nodes
- Survive and multiply in cells of the reticulo-endothelial system
- Inhibit lysosome-phagosome fusion
- Lymph nodes enlarge (lymphatic and lymphoreticular hyperplasia) and inflammation is induced
- Surviving organisms spread to other organs (liver, spleen, placenta) and cause granulomatous reactions
- Eythritol is a growth stimulant and attracts the bacteria to the bovine placenta
- Infection of foetus and abortion
Clinical disease
Diagnosis
Control
- Serological testing of milk (Milk Ring Test) and beef cattle (Rose Bengal Plate Test)
- Serological tests detect anti-lipopolysaccharide antibodies
- LPS antigen present in virulent as well as some vaccine strains therefore vaccination may confuse serological testing
- False positives due to cross-reaction with LPS in other bacteria
- Vaccination:
- Strain S19, a live vaccine, stimulating a cell-mediated immune response; vaccination of young animals; interferes with serological testing
- Newer RB51 vaccine has no LPS O-antigen therefore not detcted by serological tests
- Live attenuated Brucella melitensis vaccine to protect sheep and goats against B. melitensis
- Test and slaughter program has eradicated Brucellosis in the UK