Difference between revisions of "Brucella species"
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− | # | + | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big> |
+ | <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big> | ||
+ | |||
+ | |||
+ | |||
+ | ===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 | ||
+ | *Facultative 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=== | ||
+ | |||
+ | *Brucellae that lack outer membrane LPS (rough colonies) are less virulent than those which possess it | ||
+ | *Penetrate nasal, oral or pharyngeal mucosa | ||
+ | *Phagocytosed and carried to regional lymph nodes | ||
+ | *Smooth organisms survive and multiply in cells of the reticulo-endothelial system | ||
+ | *Inhibit lysosome-phagosome fusion | ||
+ | *Superoxide dismutase and catalase production may resist oxidative killing | ||
+ | *Lymph nodes enlarge (lymphatic and lymphoreticular hyperplasia) and inflammation is induced | ||
+ | *Surviving organisms spread to other organs (liver, [[Spleen - Anatomy & Physiology|spleen]], placenta) and cause granulomatous reactions | ||
+ | *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 | ||
+ | *Infection of foetus and abortion | ||
+ | *May localise in joints or intervertebral discs in chronic infections | ||
+ | |||
+ | |||
+ | ===Clinical disease=== | ||
+ | |||
+ | *Bovine brucellosis: | ||
+ | **Caused by ''Brucella abortus'' | ||
+ | **Eradicated in many countries including UK | ||
+ | **Infection usually by ingestions but also venereal, skin abrasions, inhalation, transplacental | ||
+ | **Abortion storms in susceptible herds | ||
+ | **Abortion after fifth month of gestation due to placentitis | ||
+ | **Brucellae excreted in foetal fluids for 2-4 weeks following abortion and at subsequent parturitions without abortion | ||
+ | **Infection of mammary glands and lymph nodes persists for years | ||
+ | **Excreted intermittently in milk for years | ||
+ | **Seminal vesicles, ampullae, testicles and epididymus infected in bulls; necrotising orchitis | ||
+ | **Decreased fertility in cows and bulls; decreased milk production | ||
+ | **Localisation in [[Spleen - Anatomy & Physiology|spleen]] and lymphatic tissue of non-pregnant animals | ||
+ | **Occasionally causes [[Joints - inflammatory#In Cattle|arthritis]] | ||
+ | *Isolated from closed cases of [[Bursae and Tendons - inflammatory#Poll Evil and Fistulous Withers|poll evil and fistulous withers]] in horses | ||
+ | *Caprine and ovine brucellosis: | ||
+ | **Caused by ''B. melitensis'' | ||
+ | **Goats more susceptible | ||
+ | **Abortion, orchitis in males, arthritis, hygromas | ||
+ | **May not have protective immunity following abortion | ||
+ | **Rose Bengal agglutination test and complement fixation test | ||
+ | **Test and slaughter where exotic | ||
+ | *Ovine epididymitis | ||
+ | **Caused by ''B. ovis'' | ||
+ | **Epididymitis in rams and placentitis in ewes | ||
+ | **Reduced fertility in rams, sporadic abortion and peinatal mortality | ||
+ | **Venereal transmission | ||
+ | **Long latent period in rams following infection (present in semen 5 weeks after infection) | ||
+ | **Premating checks on rams - serological tests and scrotal palpation | ||
+ | **Testicular atrophy and swollen epididymis in chronically-infected rams | ||
+ | **Agar gel immunodiffusion test, complement fixation test and indirect ELISA | ||
+ | **Vaccination of young rams with ''B. melitensis'' vaccine or ''B. ovis'' bacterin | ||
+ | *Porcine brucellosis: | ||
+ | **Caused by ''B. suis'' | ||
+ | **Prolonged bacteraemia | ||
+ | **Chronic inflammation in reproductive organs of boars and sows; also in joints and bones | ||
+ | **Routes of infection: ingestion or venereal | ||
+ | **Abortion, still birth, neonatal mortality, temporary sterility | ||
+ | **Boars excreting bacteria in semen may have testicular abnormalities or be normal | ||
+ | **Lameness, incoordination and posterior paralysis in joint and bone involvement | ||
+ | **Rose Bengal and indirect ELISA for diagnosis | ||
+ | **Test and slaughter where exotic | ||
+ | **Modified live ''B. suis'' vaccine | ||
+ | *Canine brucellosis: | ||
+ | **Caused by ''B. canis'' | ||
+ | **Rough therefore lower virulence - mild or asymptomatic infections | ||
+ | **Abortions, decreased fertility, reduced litter sizes, neonatal mortality | ||
+ | **Orchitis and epididymitis causing infertility in male dogs | ||
+ | **Infertility may be permanent if chronic infection | ||
+ | **Slide agglutination, ELISA, agar gel immunodiffusion | ||
+ | **Neuter infected animals | ||
+ | *Human brucellosis: | ||
+ | **Susceptible to ''B. abortus, B. suis, B. melitensis'' and ''B. canis'' | ||
+ | **Transmission via contact with secretions from infected animals | ||
+ | **Routes of infection: skin abrasions, inhalation, ingestion | ||
+ | **Unpasteurised milk source of infection | ||
+ | **Undulant fever - fluctuating pyrexia, malaise, fatigue, muscle and joint pains, osteomyelitis | ||
+ | **Can become chronic | ||
+ | **''B melitensis'' and ''B. suis'' cause most severe infections | ||
+ | **Antimicrobials | ||
+ | |||
+ | |||
+ | |||
+ | ===Diagnosis=== | ||
+ | |||
+ | *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 | ||
+ | *Modified Ziehl-Neelson stains reveal organisms in samples from cotyledons, uterine discharge and foetal abomasal contents | ||
+ | *PCR for detection in tissue | ||
+ | *Brucellin for intradermal testing for ''B. abortus'' | ||
+ | *Enriched media for isolation | ||
+ | *Complement fixation test | ||
+ | *Indirect and competitive ELISA | ||
+ | *Serum agglutination test | ||
+ | *Antiglobulin test | ||
+ | |||
+ | |||
+ | ===Control=== | ||
+ | |||
+ | *Test and slaughter program has eradicated bovine brucellosis in the UK | ||
+ | *Vaccination of heifers against ''B. abortus'' in endemic regions: | ||
+ | **Strain S19, a live attenuated vaccine, stimulating a cell-mediated immune response; vaccination of young animals; interferes with serological testing | ||
+ | **45/20 bacterin vaccine less effective | ||
+ | **Newer RB51 vaccine has no LPS O-antigen therefore not detected by serological tests and gives good protection | ||
+ | *Live attenuated ''Brucella melitensis'' vaccine to protect lambs and kids against ''B. melitensis'' |
Revision as of 15:50, 18 August 2008
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
- Facultative 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
- Brucellae that lack outer membrane LPS (rough colonies) are less virulent than those which possess it
- Penetrate nasal, oral or pharyngeal mucosa
- Phagocytosed and carried to regional lymph nodes
- Smooth organisms survive and multiply in cells of the reticulo-endothelial system
- Inhibit lysosome-phagosome fusion
- Superoxide dismutase and catalase production may resist oxidative killing
- 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 placenta of cattle, sheep, goats and pigs; also found in mammary gland and epididymis, targets for brucellae
- Infection of foetus and abortion
- May localise in joints or intervertebral discs in chronic infections
Clinical disease
- Bovine brucellosis:
- Caused by Brucella abortus
- Eradicated in many countries including UK
- Infection usually by ingestions but also venereal, skin abrasions, inhalation, transplacental
- Abortion storms in susceptible herds
- Abortion after fifth month of gestation due to placentitis
- Brucellae excreted in foetal fluids for 2-4 weeks following abortion and at subsequent parturitions without abortion
- Infection of mammary glands and lymph nodes persists for years
- Excreted intermittently in milk for years
- Seminal vesicles, ampullae, testicles and epididymus infected in bulls; necrotising orchitis
- Decreased fertility in cows and bulls; decreased milk production
- Localisation in spleen and lymphatic tissue of non-pregnant animals
- Occasionally causes arthritis
- Isolated from closed cases of poll evil and fistulous withers in horses
- Caprine and ovine brucellosis:
- Caused by B. melitensis
- Goats more susceptible
- Abortion, orchitis in males, arthritis, hygromas
- May not have protective immunity following abortion
- Rose Bengal agglutination test and complement fixation test
- Test and slaughter where exotic
- Ovine epididymitis
- Caused by B. ovis
- Epididymitis in rams and placentitis in ewes
- Reduced fertility in rams, sporadic abortion and peinatal mortality
- Venereal transmission
- Long latent period in rams following infection (present in semen 5 weeks after infection)
- Premating checks on rams - serological tests and scrotal palpation
- Testicular atrophy and swollen epididymis in chronically-infected rams
- Agar gel immunodiffusion test, complement fixation test and indirect ELISA
- Vaccination of young rams with B. melitensis vaccine or B. ovis bacterin
- Porcine brucellosis:
- Caused by B. suis
- Prolonged bacteraemia
- Chronic inflammation in reproductive organs of boars and sows; also in joints and bones
- Routes of infection: ingestion or venereal
- Abortion, still birth, neonatal mortality, temporary sterility
- Boars excreting bacteria in semen may have testicular abnormalities or be normal
- Lameness, incoordination and posterior paralysis in joint and bone involvement
- Rose Bengal and indirect ELISA for diagnosis
- Test and slaughter where exotic
- Modified live B. suis vaccine
- Canine brucellosis:
- Caused by B. canis
- Rough therefore lower virulence - mild or asymptomatic infections
- Abortions, decreased fertility, reduced litter sizes, neonatal mortality
- Orchitis and epididymitis causing infertility in male dogs
- Infertility may be permanent if chronic infection
- Slide agglutination, ELISA, agar gel immunodiffusion
- Neuter infected animals
- Human brucellosis:
- Susceptible to B. abortus, B. suis, B. melitensis and B. canis
- Transmission via contact with secretions from infected animals
- Routes of infection: skin abrasions, inhalation, ingestion
- Unpasteurised milk source of infection
- Undulant fever - fluctuating pyrexia, malaise, fatigue, muscle and joint pains, osteomyelitis
- Can become chronic
- B melitensis and B. suis cause most severe infections
- Antimicrobials
Diagnosis
- 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
- Modified Ziehl-Neelson stains reveal organisms in samples from cotyledons, uterine discharge and foetal abomasal contents
- PCR for detection in tissue
- Brucellin for intradermal testing for B. abortus
- Enriched media for isolation
- Complement fixation test
- Indirect and competitive ELISA
- Serum agglutination test
- Antiglobulin test
Control
- Test and slaughter program has eradicated bovine brucellosis in the UK
- Vaccination of heifers against B. abortus in endemic regions:
- Strain S19, a live attenuated vaccine, stimulating a cell-mediated immune response; vaccination of young animals; interferes with serological testing
- 45/20 bacterin vaccine less effective
- Newer RB51 vaccine has no LPS O-antigen therefore not detected by serological tests and gives good protection
- Live attenuated Brucella melitensis vaccine to protect lambs and kids against B. melitensis