Difference between revisions of "Brucella species"

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#REDIRECT[[:Category:Brucella species]]
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{{review}}
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{{toplink
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|backcolour =
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|linkpage =Bacteria
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|linktext =BACTERIA
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|pagetype=Bugs
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}}
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<br>
 +
===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 - Pathology#In Cattle|arthritis]]
 +
*Isolated from closed cases of [[Bursae and Tendons Inflammatory - Pathology#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 09:40, 25 September 2008

 This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing.


Infectious agents and parasitesWikiBugs Banner.png
BACTERIA



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
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