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Leptospirosis

Aetiology
1. aquatic spirochetes
2. hardjo serovar in UK
  1. Leptospira borgpetersenii - Hardjo
  2. Leptospira interrogans - Hardjo
  3. serologically indistinguishable
3. L. pomona or L. icterohermorrhagica
  1. severe disease
  2. considerably less common
4. Public health risk
  1. flu like symptoms
5. Pathogenesis
  1. penetration of MM
    Annotations:
    - oral, GIT, repro
    1. penetration of skin barrier
      Annotations:
      - water damage
    2. bacteremia for 6-9 days
      1. humoral antibodies
      2. hematogenous spread
        renal shedding in 14 days
        persistent for months
  2. transmission
    1. contact with contaminated urine
      1. pasture can remain infectious for 2 months
    2. abortive products
    3. venerial from bulls
    4. hardjo NOT carried by wildlife
    5. sheep carriers, not clinical
Risk Factors
1. open herd
2. shared bulls
3. mixed grazing with sheep
4. shared grazing/water courses
  1. between herds or with sheep
Clinical Signs
1. Milk drop
  1. sudden drop or stop
    1. ''flabby bag''
  2. thick colostrums or blood tinge
  3. lethargy and pyrexia
2. generally none in endemic herds
3. Abortion
  1. 3-12 weeks post infection
  2. last trimester
    1. significant economic loss
  3. weak or premature calves
4. Infertillity
  1. circumstantially indicated
  2. improved by vaccine vs endemic immunity
Diagnosis
1. Milk Drop
  1. paired serology @3-4 weeks
    1. seroconversion
  2. antibiotics interfere
  3. leptospires in urine
    1. microscopy
    2. PCR
2. Abortion
  1. maternal serology USELESS
  2. aborted fetus
    1. antibodies in fetal fluid
    2. fluorescent antibody test
      Annotations:
      - must be performed ASAP because Bacteria decompose quickly
3. Herd screening
  1. test 25%
    1. some +ve = probably outbreak in past
    2. many +ve = outbreak recently
    3. high titres = active invection
    4. Enter text here
Treatment
1. Streptomycin
  1. single i/m dose works for most cases
  2. prevents carriers
2. oxytetracycline/amoxycillin
  1. may allow some to remain carriers
Prevention
1. managment
  1. closed herd
    1. avoid mixing with sheep
    2. avoid shared water courses
  2. during acute infeciton
    1. whole herd antibiotics
    2. vaccine program
      1. vaccinate heifers before entering herd
  3. endemic infection
    1. complete heifer vaccination before breeding
    2. vaccines economical?
      1. annual boosters to protect herdsmen
2. adjuvanted vaccines
  1. 2 @ 4 weeks
  2. ELISA to check titres
  3. prevents urine shedding
  4. protects against milk drop and abortion
key points
1. blood tests cannot determine state of infection
2. serology can diagnose acute infection
3. most common source is bought on or borrowed animals
  1. shared grazing/water source with sheep may cause infection
  2. may be carried by sheep but NOT wildlife
4. clinical disease may only be apparent as acute infection enters the herd
5. vaccines prevent clinical signs and reduce shedding, do not eradicate
6. herdsmen must be protected from infection
  1. control of substances hazardous to health (COSHH) regulations

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Leptospirosis

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	Created by m.n.palmer over 10 years ago