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| − | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
| + | #REDIRECT[[:Category:Brucella species]] |
| − | <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
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| − | ===Overview===
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| − | *Important zoonoses worldwide
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| − | *Cause chronic granulomatous diseases
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| − | *6 species
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| − | *Target reproductive organs of certain species
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| − | *Infected animals act as reservoir of infection
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| − | *Organisms can remain viable in moist environment for months
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| − | *Cause undulant fever in humans
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| − | ===Characteristics===
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| − | *Small, non-moltile, Gram negative coccobacilli
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| − | *Facultative intracellular pathogens
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| − | *Modified Ziehl-Neelsen positive - clusters of red coccobacilli on smears
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| − | *Aerobic and capnophilic
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| − | *Catalase positive; oxidase and urease positive except for ''Brucella ovis''
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| − | *Some species require enriched media for growth
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| − | *Non-haemolytic
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| − | *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
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| − | *Rough colonies of ''B. ovis'' and ''B. canis'' are dull, yellow, opaque and friable
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| − | *Slide agglutination with speicific antisera detect important antigens
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| − | *''B. abortus'' lysed by specific bacterophages
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| − | *Oxidative metaboloic rates can differentiate species
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| − | ===Pathogenesis and pathogenicity===
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| − | *Brucellae that lack outer membrane LPS (rough colonies) are less virulent than those which possess it
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| − | *Penetrate nasal, oral or pharyngeal mucosa
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| − | *Phagocytosed and carried to regional lymph nodes
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| − | *Smooth organisms survive and multiply in cells of the reticulo-endothelial system
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| − | *Inhibit lysosome-phagosome fusion
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| − | *Superoxide dismutase and catalase production may resist oxidative killing
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| − | *Lymph nodes enlarge (lymphatic and lymphoreticular hyperplasia) and inflammation is induced
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| − | *Surviving organisms spread to other organs (liver, [[Spleen - Anatomy & Physiology|spleen]], placenta) and cause granulomatous reactions
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| − | *Eythritol is a growth stimulant and attracts the bacteria to the placenta of cattle, sheep, goats and pigs; also found in mammary gland and epididymis, targets for brucellae
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| − | *Infection of foetus and abortion
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| − | *May localise in joints or intervertebral discs in chronic infections
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| − | ===Clinical disease===
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| − | *Bovine brucellosis:
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| − | **Caused by ''Brucella abortus''
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| − | **Eradicated in many countries including UK
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| − | **Infection usually by ingestions but also venereal, skin abrasions, inhalation, transplacental
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| − | **Abortion storms in susceptible herds
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| − | **Abortion after fifth month of gestation due to placentitis
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| − | **Brucellae excreted in foetal fluids for 2-4 weeks following abortion and at subsequent parturitions without abortion
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| − | **Infection of mammary glands and lymph nodes persists for years
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| − | **Excreted intermittently in milk for years
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| − | **Seminal vesicles, ampullae, testicles and epididymus infected in bulls; necrotising orchitis
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| − | **Decreased fertility in cows and bulls; decreased milk production
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| − | **Localisation in [[Spleen - Anatomy & Physiology|spleen]] and lymphatic tissue of non-pregnant animals
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| − | **Occasionally causes [[Joints Inflammatory - Pathology#In Cattle|arthritis]]
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| − | *Isolated from closed cases of [[Bursae and Tendons - inflammatory#Poll Evil and Fistulous Withers|poll evil and fistulous withers]] in horses
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| − | *Caprine and ovine brucellosis:
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| − | **Caused by ''B. melitensis''
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| − | **Goats more susceptible
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| − | **Abortion, orchitis in males, arthritis, hygromas
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| − | **May not have protective immunity following abortion
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| − | **Rose Bengal agglutination test and complement fixation test
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| − | **Test and slaughter where exotic
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| − | *Ovine epididymitis
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| − | **Caused by ''B. ovis''
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| − | **Epididymitis in rams and placentitis in ewes
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| − | **Reduced fertility in rams, sporadic abortion and peinatal mortality
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| − | **Venereal transmission
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| − | **Long latent period in rams following infection (present in semen 5 weeks after infection)
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| − | **Premating checks on rams - serological tests and scrotal palpation
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| − | **Testicular atrophy and swollen epididymis in chronically-infected rams
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| − | **Agar gel immunodiffusion test, complement fixation test and indirect ELISA
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| − | **Vaccination of young rams with ''B. melitensis'' vaccine or ''B. ovis'' bacterin
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| − | *Porcine brucellosis:
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| − | **Caused by ''B. suis''
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| − | **Prolonged bacteraemia
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| − | **Chronic inflammation in reproductive organs of boars and sows; also in joints and bones
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| − | **Routes of infection: ingestion or venereal
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| − | **Abortion, still birth, neonatal mortality, temporary sterility
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| − | **Boars excreting bacteria in semen may have testicular abnormalities or be normal
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| − | **Lameness, incoordination and posterior paralysis in joint and bone involvement
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| − | **Rose Bengal and indirect ELISA for diagnosis
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| − | **Test and slaughter where exotic
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| − | **Modified live ''B. suis'' vaccine
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| − | *Canine brucellosis:
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| − | **Caused by ''B. canis''
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| − | **Rough therefore lower virulence - mild or asymptomatic infections
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| − | **Abortions, decreased fertility, reduced litter sizes, neonatal mortality
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| − | **Orchitis and epididymitis causing infertility in male dogs
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| − | **Infertility may be permanent if chronic infection
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| − | **Slide agglutination, ELISA, agar gel immunodiffusion
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| − | **Neuter infected animals
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| − | *Human brucellosis:
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| − | **Susceptible to ''B. abortus, B. suis, B. melitensis'' and ''B. canis''
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| − | **Transmission via contact with secretions from infected animals
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| − | **Routes of infection: skin abrasions, inhalation, ingestion
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| − | **Unpasteurised milk source of infection
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| − | **Undulant fever - fluctuating pyrexia, malaise, fatigue, muscle and joint pains, osteomyelitis
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| − | **Can become chronic
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| − | **''B melitensis'' and ''B. suis'' cause most severe infections
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| − | **Antimicrobials
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| − | ===Diagnosis===
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| − | *Serological testing of milk (Milk Ring Test) and beef cattle (Rose Bengal Plate Test)
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| − | *Serological tests detect anti-lipopolysaccharide antibodies
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| − | *LPS antigen present in virulent as well as some vaccine strains therefore vaccination may confuse serological testing
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| − | *False positives due to cross-reaction with LPS in other bacteria
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| − | *Modified Ziehl-Neelson stains reveal organisms in samples from cotyledons, uterine discharge and foetal abomasal contents
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| − | *PCR for detection in tissue
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| − | *Brucellin for intradermal testing for ''B. abortus''
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| − | *Enriched media for isolation
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| − | *Complement fixation test
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| − | *Indirect and competitive ELISA
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| − | *Serum agglutination test
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| − | *Antiglobulin test
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| − | ===Control===
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| − | *Test and slaughter program has eradicated bovine brucellosis in the UK
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| − | *Vaccination of heifers against ''B. abortus'' in endemic regions:
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| − | **Strain S19, a live attenuated vaccine, stimulating a cell-mediated immune response; vaccination of young animals; interferes with serological testing
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| − | **45/20 bacterin vaccine less effective
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| − | **Newer RB51 vaccine has no LPS O-antigen therefore not detected by serological tests and gives good protection
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| − | *Live attenuated ''Brucella melitensis'' vaccine to protect lambs and kids against ''B. melitensis''
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