Difference between revisions of "Brucella species"

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#REDIRECT[[:Category: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
 +
*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===
 +
 
 +
*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 16:45, 17 July 2008

BACK TO INFECTIOUS AGENTS AND PARASITES
BACK TO 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
  • 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

  • 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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