Difference between revisions of "Spirochaetes"

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#REDIRECT[[:Category:Spirochaetes]]
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===Overview===
 +
 
 +
*Two families exist, ''Leptospiraceae'' and ''Spirochaetaceae''
 +
*''Leptospiraceae'' include the pathogens of the genus ''Leptospira''
 +
*''Spirochaetaceae'' include the pathogens of the genera ''Borrelia'', ''Brachyspira'' and ''Treponema''
 +
*Many cause zoonotic infections
 +
 
 +
 
 +
 
 +
===Characteristics===
 +
 
 +
*Spiral or helical Gram-negative bacteria
 +
*Motile organisms via endoflagella
 +
*Poor survival in the environment and sensitive to dessication
 +
*Stain poorly with Gram stain
 +
*Most require specialised media for growth
 +
*Serology required for identification
 +
 
 +
 
 +
===''Leptospira''===
 +
 
 +
*Motile, helical bacteria found in aquatic environments
 +
*Require liquid media for culture
 +
*Cause leptospirosis in all animals, which can range from mild urogenital tract infections to systemic diseases
 +
*Organisms persist in kidney tubules or genital tract of carrier animals and are shed in urine
 +
*Transmission via direct contact
 +
*Serovars are fairly host-specific, causing mild disease in the maintenance host, with shedding in the urine
 +
*Maintenance hosts may transmit the infection to incidental hosts, which are less susceptible to infection, but develop serious disease
 +
 
 +
*Pathogenesis and pathogenicity
 +
**Depends on virulence of the serovar and susceptibility of the host
 +
**Leptospires invade tissues through moist skin or via mucous membranes, aided by their motility
 +
**Leptospires may invade via receptor-mediatied endocytosis
 +
**They disseminate through the body via the blood stream
 +
**Antibodies clear organisms from the blood stream after about 10 days of infection
 +
**Organisms may persist in the renal tubules, uterus, eye or meninges
 +
**Evade phagocytosis possibly via macrophage apoptosis
 +
**Damage red blood cell membranes and endothelial and liver cells, leading to haemolytic anaemia, jaundice, haemoglobinuria and haemorrhage in acute leptospirosis
 +
 
 +
*Diagnosis
 +
**Clinical signs and history of exposure
 +
**Dark-field microscopy of urine may detect organisms
 +
**Isolation from blood or urine by culture or animal inoculation
 +
**Identificaiton or certain serovars using DNA probes and serology
 +
**FLuorescent antibody technique for identification in tissues
 +
**Silver impregnation
 +
**Molecular techniques such as PCR
 +
**Serology using microscopic agglutination test or ELISA
 +
 
 +
*Clinical infections
 +
**Cattle and sheep
 +
***Cattle are maintenance hosts for ''L. borgpetersenii'' serovar ''hardjo''
 +
***''L. interrogans'' serovar ''hardjo'' is host-adapted to cattle
 +
***Acute disease in susceptible heifers, with fever and agalactia of all quarters; abortion and stillbirth may occur
 +
***Diagnosed by rising antibody titre in paired serum samples
 +
***Infection in sheep may cause abortion and agalactia
 +
***Urinary excretion can be reduced by administering dihydrostreptomycin or amoxycillin
 +
***Incactivated vaccines are of questionable efficacy
 +
***Serovars ''pomona, grippotyphosa'' and ''icterohaemorrhagiae'' cause pyrexia, haemoglobinurea, jaundice, anorexia, uraemia due to renal damage and death in calves and lambs
 +
 
 +
**Horses
 +
***Clinical disease rare
 +
***May be maintenance host of serovar ''bratislava'', which causes abortion and stillbirth
 +
***Incidental hosts for serovar ''pomona'', suffering from abortion and renal disease
 +
***Chronic leptospirosis may cause an immune-mediated anterior uveitis
 +
 
 +
**Pigs
 +
***The rodent-adapted serovars ''icterohaemorrhagica'' and ''copenhagenii'' cause acute disease in pigs
 +
***Severe disease in young pigs
 +
***Serovar ''pomona'' is the host-adapted species, and may be shed in the urine
 +
***Infections may cause abortions and stillbirths
 +
***Pigs are maintenance hosts for serovars ''tarassovi'' and ''bratislava'', which may cause reproductive failure
 +
 
 +
**Dogs and cats
 +
***Serovars ''canicola'' and ''icterohaemorrhagica'' cause leptospirosis in dogs, but are vaccinated against
 +
***Serovars ''pomona'' and ''grippotyphosa'' are becoming important
 +
***The host-adapted serovar ''canicolar'' causes acute renal failure in puppies; a chronic uraemic syndrome may follow
 +
***Incidental infections with serovar ''icterohaemorrhagica'' or ''copenhagenii'' cause renal failure
 +
***Serovar ''bratislava'' causes abortion and infertility in dogs, which may be the maintenance host
 +
***Infections uncommon in cats
 +
 
 +
 
 +
===''Borrelia''===
 +
 
 +
*Longer, wider, helical spirochaetes with a linear chromosome and linear and circular plasmids
 +
*Obligate parasites transmitted by arthropod vectors
 +
 
 +
*Lyme disease
 +
**Caused by ''Borrelia burgdorferi''
 +
**Reported in humans, dogs, horses, cattle, sheep
 +
 
 +
 +
[[Brachyspira hyodysenteriae]]
 +
 
 +
[[Leptospira]]

Revision as of 10:34, 31 December 2008

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BACTERIA



Overview

  • Two families exist, Leptospiraceae and Spirochaetaceae
  • Leptospiraceae include the pathogens of the genus Leptospira
  • Spirochaetaceae include the pathogens of the genera Borrelia, Brachyspira and Treponema
  • Many cause zoonotic infections


Characteristics

  • Spiral or helical Gram-negative bacteria
  • Motile organisms via endoflagella
  • Poor survival in the environment and sensitive to dessication
  • Stain poorly with Gram stain
  • Most require specialised media for growth
  • Serology required for identification


Leptospira

  • Motile, helical bacteria found in aquatic environments
  • Require liquid media for culture
  • Cause leptospirosis in all animals, which can range from mild urogenital tract infections to systemic diseases
  • Organisms persist in kidney tubules or genital tract of carrier animals and are shed in urine
  • Transmission via direct contact
  • Serovars are fairly host-specific, causing mild disease in the maintenance host, with shedding in the urine
  • Maintenance hosts may transmit the infection to incidental hosts, which are less susceptible to infection, but develop serious disease
  • Pathogenesis and pathogenicity
    • Depends on virulence of the serovar and susceptibility of the host
    • Leptospires invade tissues through moist skin or via mucous membranes, aided by their motility
    • Leptospires may invade via receptor-mediatied endocytosis
    • They disseminate through the body via the blood stream
    • Antibodies clear organisms from the blood stream after about 10 days of infection
    • Organisms may persist in the renal tubules, uterus, eye or meninges
    • Evade phagocytosis possibly via macrophage apoptosis
    • Damage red blood cell membranes and endothelial and liver cells, leading to haemolytic anaemia, jaundice, haemoglobinuria and haemorrhage in acute leptospirosis
  • Diagnosis
    • Clinical signs and history of exposure
    • Dark-field microscopy of urine may detect organisms
    • Isolation from blood or urine by culture or animal inoculation
    • Identificaiton or certain serovars using DNA probes and serology
    • FLuorescent antibody technique for identification in tissues
    • Silver impregnation
    • Molecular techniques such as PCR
    • Serology using microscopic agglutination test or ELISA
  • Clinical infections
    • Cattle and sheep
      • Cattle are maintenance hosts for L. borgpetersenii serovar hardjo
      • L. interrogans serovar hardjo is host-adapted to cattle
      • Acute disease in susceptible heifers, with fever and agalactia of all quarters; abortion and stillbirth may occur
      • Diagnosed by rising antibody titre in paired serum samples
      • Infection in sheep may cause abortion and agalactia
      • Urinary excretion can be reduced by administering dihydrostreptomycin or amoxycillin
      • Incactivated vaccines are of questionable efficacy
      • Serovars pomona, grippotyphosa and icterohaemorrhagiae cause pyrexia, haemoglobinurea, jaundice, anorexia, uraemia due to renal damage and death in calves and lambs
    • Horses
      • Clinical disease rare
      • May be maintenance host of serovar bratislava, which causes abortion and stillbirth
      • Incidental hosts for serovar pomona, suffering from abortion and renal disease
      • Chronic leptospirosis may cause an immune-mediated anterior uveitis
    • Pigs
      • The rodent-adapted serovars icterohaemorrhagica and copenhagenii cause acute disease in pigs
      • Severe disease in young pigs
      • Serovar pomona is the host-adapted species, and may be shed in the urine
      • Infections may cause abortions and stillbirths
      • Pigs are maintenance hosts for serovars tarassovi and bratislava, which may cause reproductive failure
    • Dogs and cats
      • Serovars canicola and icterohaemorrhagica cause leptospirosis in dogs, but are vaccinated against
      • Serovars pomona and grippotyphosa are becoming important
      • The host-adapted serovar canicolar causes acute renal failure in puppies; a chronic uraemic syndrome may follow
      • Incidental infections with serovar icterohaemorrhagica or copenhagenii cause renal failure
      • Serovar bratislava causes abortion and infertility in dogs, which may be the maintenance host
      • Infections uncommon in cats


Borrelia

  • Longer, wider, helical spirochaetes with a linear chromosome and linear and circular plasmids
  • Obligate parasites transmitted by arthropod vectors
  • Lyme disease
    • Caused by Borrelia burgdorferi
    • Reported in humans, dogs, horses, cattle, sheep


Brachyspira hyodysenteriae

Leptospira

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