Difference between revisions of "Spirochaetes"
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+ | {{toplink | ||
+ | |backcolour = | ||
+ | |linkpage =Bacteria | ||
+ | |linktext =BACTERIA | ||
+ | |pagetype=Bugs | ||
+ | }} | ||
+ | <br> | ||
− | # | + | ===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 | ||
+ | * May cause severe systemic disease, resulting in [[Intestines Fibrinous/Haemorrhagic Enteritis - Pathology#Bacterial septicaemia and enteritis|enteritis]] | ||
+ | |||
+ | *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-mediated 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, [[General Pathology - Pigmentation and Calcification#Haemoglobin|haemoglobin pigmentation]], 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 | ||
+ | ***''L. icterohaemorrhagiae'' may cause [[General Pathology - Pigmentation and Calcification#Hepatic (Toxic) Icterus|hepatic jaundice]] | ||
+ | ***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 | ||
+ | **Ticks are the vector, which acquire the infection from small rodents, the reservoir hosts | ||
+ | **Ticks transmit the infection to large mammals such as deer and sheep | ||
+ | **''Ixodes ricinus'' is the most common tick vector in Europe | ||
+ | |||
+ | |||
+ | [[Brachyspira hyodysenteriae]] |
Revision as of 10:43, 31 December 2008
|
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
- May cause severe systemic disease, resulting in enteritis
- 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-mediated 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, haemoglobin pigmentation, 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
- Cattle and sheep
- 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
- Horses
- 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
- Pigs
- 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
- L. icterohaemorrhagiae may cause hepatic jaundice
- Serovar bratislava causes abortion and infertility in dogs, which may be the maintenance host
- Infections uncommon in cats
- Dogs and 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
- Ticks are the vector, which acquire the infection from small rodents, the reservoir hosts
- Ticks transmit the infection to large mammals such as deer and sheep
- Ixodes ricinus is the most common tick vector in Europe