|
|
(6 intermediate revisions by 2 users not shown) |
Line 1: |
Line 1: |
− | {{toplink
| |
− | |backcolour =
| |
− | |linkpage =Bacteria
| |
− | |linktext =BACTERIA
| |
− | |pagetype=Bugs
| |
− | }}
| |
− | <br>
| |
| | | |
− | ===Overview===
| + | #REDIRECT[[:Category:Spirochaetes]] |
− | | |
− | *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]]
| |