Difference between revisions of "Spirochaetes"
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*Serovars are fairly host-specific, causing mild disease in the maintenance host, with shedding in the urine | *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 | *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 | *Pathogenesis and pathogenicity | ||
**Depends on virulence of the serovar and susceptibility of the host | **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 invade tissues through moist skin or via mucous membranes, aided by their motility | ||
− | **Leptospires may invade via receptor- | + | **Leptospires may invade via receptor-mediated endocytosis |
**They disseminate through the body via the blood stream | **They disseminate through the body via the blood stream | ||
**Antibodies clear organisms from the blood stream after about 10 days of infection | **Antibodies clear organisms from the blood stream after about 10 days of infection | ||
**Organisms may persist in the renal tubules, uterus, eye or meninges | **Organisms may persist in the renal tubules, uterus, eye or meninges | ||
**Evade phagocytosis possibly via macrophage apoptosis | **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 | + | **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 | *Diagnosis | ||
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***The host-adapted serovar ''canicolar'' causes acute renal failure in puppies; a chronic uraemic syndrome may follow | ***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 | ***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 | ***Serovar ''bratislava'' causes abortion and infertility in dogs, which may be the maintenance host | ||
***Infections uncommon in cats | ***Infections uncommon in cats |
Revision as of 10:38, 31 December 2008
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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
- 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