Brucella

Habitat, nutrients, energy and oxygen
1. Habitat
  1. Zoonotic – passed by contact and by aerosol
  2. Highly infectious
  3. Obligate parasites in preferred natural host
  4. Poor environmental survival
    1. Few hours unprotected in sunlight
    2. Days protected by urine/aborted material
    3. Months protected by damp/cool weather
  5. Wild animal reservoir
2. Species and biotypes
  1. 7 species
  2. Urease activity and H2S production
  3. CO2 requirement
    1. Capnophilic
      1. Multiply in host
  4. Sensitivity to dyes (basic fuchsin & thionin)
  5. Phage typing
    1. Only for outbreak investigation
  6. Presence of antigens
    1. A and M: B. abortus, B. melitensis, B. suis
    2. R: B. ovis, B. canis
3. Small gram -ve coccobacilli
  1. Ovoid shape
4. Non-motile
5. Non-sporing
6. Catalase +
7. Oxidase + (variable)
8. Aerobic
9. Fastidious (difficult to grow)
  1. Blood / serum - yes
  2. BLA - no
  3. Selective media - yes
Diseases caused
1. B. abortus
  1. Cattle
    1. Placentitis
    2. Abortion
    3. Mastitis
    4. Orchitis
    5. Still causes mastitis and abortion when endemic
  2. Sheep, goats, pigs
    1. Abortion
  3. Horses
    1. Suppurative bursitis (poll evil, fistulous withers)
    2. Lesions in tendons and joints (arthritic disease)
  4. Humans
    1. Undulant fever
2. B. melitensis
  1. Goats, sheep
    1. Abortion
    2. Mastitis
    3. Orchitis
  2. Cattle
    1. Abortion
  3. Humans
    1. Undulant fever
      1. Tends to be found abroad
      2. 'Malta fever'
3. B. suis
  1. Pigs
    1. Abortion
    2. Orchitis
    3. Infertility
    4. Arthritis
    5. Spondylitis
  2. Horses
    1. Suppurative bursitis (poll evil, fistulous withers)
  3. Humans
    1. Undulant fever
4. B. ovis
  1. Sheep
    1. Placentitis
    2. Abortion
    3. Orchitis
    4. Infertility
    5. Epididymitis
5. B. canis
  1. Dogs, foxes
    1. Abortion
    2. Epididymitis
    3. Osteomyelitis
    4. Spondylitis
    5. Permanent infertility in males
  2. Humans
    1. Undulant fever
6. B. neotomae
  1. Non-pathogenic
  2. Found only in the desert wood rat of Utah
7. B. maris
  1. Marine animals
  2. Proposed new species
8. As a group of organisms, they tend to cause abortion
9. Major concerns
  1. Long term udder damage + milk loss
  2. Arthritis / bursitis
  3. Zoonotic
  4. Economic losses
Process of disease
1. Pathogenesis
  1. Predilection for reproductive tracts (RT)
    1. Erythritol - stimulates growth of B.abortus/melitensis/suis
    2. High levels in male/female RT
    3. Absent from human RT
      1. Not an abortive disease in humans – is instead a joint disease
  2. Survival in PMNs and macrophages
  3. Persistence in macrophages
  4. Swelling, inflammation, haemorrhage
2. Immune response
  1. IgM and IgG
  2. Cell mediated immune response
    1. Cleared from genital tract
    2. Persist in RES and udder
    3. Recurrent infection
  3. Carrier animals
    1. Abort once
    2. Less severe infection at subsequent pregnancies
      1. Due to adaptive immune response
    3. Excrete in udder + uterine discharge
3. Calves born to carrier cows
  1. Infected in utero or via milk
  2. Prepubescent = relatively resistant
    1. Reproductive system not developed enough, not enough erythritol for clinical disease
  3. Develop a good immune response
  4. Most clear infection and remain R
  5. ≈ 2% retain latent infection
    1. Source of infection for others
    2. Have infected calves themselves
4. Routes of infection
  1. Mucous membranes: usually ingestion
  2. Via unbroken skin
  3. Venereally
  4. To calf in utero
  5. To calf via milk
Control measures
1. Vaccination
  1. Strain 19
    1. Used in original eradication scheme
    2. Live attenuated
    3. Rarely shed in milk
    4. Huge doses needed - abortion in cows
    5. Non-tranmissable
    6. Female calves @ 2-5 months
      1. More likely to shed than male calves
      2. Male calves not vaccinated
    7. Adults develop persistent antibodies
    8. Infects humans
    9. Would persist in the body long enough to cause abortion
  2. 45/20 (no longer used)
    1. Killed bacterin (rough mutant)
      1. No LPS
    2. Less effective but adults don’t develop persistent antibody levels
  3. RB51 (licensed for use in USA)
    1. Stable rough mutant
      1. No LPS or flagella, but does have proteins – antibodies recognise this and will recognise the proteins on the true bacteria as a result
    2. Good protection v abortion
    3. Ab’s don’t interfere with serological tests
2. Isolation
  1. Isolate from blood culture on Castaneda’s medium
  2. Simultaneous solid and liquid culture
  3. Prolonged incubation >6 months
  4. Must be differentiated from Salmonella
    1. Brucella is urease positive
    2. Similar antibodies
  5. B. abortus requires elevated CO2
3. Treatment
  1. Lack of clinical trials
  2. Antibiotics rarely used – will kill instead
    1. Poor perfusion into joints, where bacteria are found
  3. Oxytetracycline and streptomycin has shown efficacy
    1. Work in people
  4. Not yet endemic worldwide, so eradication scheme was effective as we are an island
4. Testing
  1. ID infected herds
    1. ELISA on bulk milk
      1. Quarterly by APHA
  2. ID infected individuals
    1. Bacterial culture
    2. Direct microscopy
      1. Immunofluorescence
      2. Modified Ziehl-Neelsen
      3. Takes a long time to grow, hence use of this method
    3. PCR
    4. Guinea pig inoculation
    5. Serology
      1. Slide agglutination (card test, plate test)
      2. Serum agglutination test (SAT)
      3. Complement fixation test
      4. ELISA
5. Eradication scheme
  1. Identify infected herds
    1. Identify infected individuals
      1. Cull infected individuals
        Compensation (75% of market value)
    2. Herd restrictions
      1. Retested at 8 months and 12 months
        No positives - restrictions lifted
        Positives - culled (with dangerous contacts) + herd tested every 2 months until cleared
  2. Regular testing programme
    1. Dairy herds – monthly
    2. Beef cattle - every 2 years
    3. Imported cattle
    4. Abortions
6. NOTIFIABLE
  1. Common in other parts of the world
  2. Could be imported

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Brucella

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	Created by Jess Pope almost 8 years ago