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*Longer, wider, helical spirochaetes with a linear chromosome and linear and circular plasmids
 
*Longer, wider, helical spirochaetes with a linear chromosome and linear and circular plasmids
 
*Obligate parasites transmitted by arthropod vectors
 
*Obligate parasites transmitted by arthropod vectors
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*Cause systemic infections in many animals and humans
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*Slow growth in specialised culture media
    
*Lyme disease
 
*Lyme disease
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**Ticks transmit the infection to large mammals such as deer and sheep  
 
**Ticks transmit the infection to large mammals such as deer and sheep  
 
**''Ixodes ricinus'' is the most common tick vector in Europe
 
**''Ixodes ricinus'' is the most common tick vector in Europe
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**Pathogenesis
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***Virulence of the borreliae requires a change in expression of an outer membrane protein following ingestion of blood by the tick
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***Borreliae multiply in the blood stream of susceptible hosts and disseminate throughout the body
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***Localisation in joints, brain, nerves, eyes and heart can occur
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***The associated lesions may be in part caused by the host immune response
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**CLinical signs
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***May be subclinical in endemic areas
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***Clinical manifestation depends on the site of localisation of organisms
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***Disease in dogs may cause fever, lethargy, arthritis, cardiac, renal or neurological disturbance
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***Horses suffer similar clinical signs but also lameness, uveitis, nephritis, hepatitis and encephalitis
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***Cattle and sheep may suffer from lameness
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**Diagnosis
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***Laboratory confirmation difficult due to low numbers of organisms and fastidious growth requirements
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***History of exposure to ticks in an endemic region and clinical signs
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***Rising antibody titre to ''Borrelia burgdorferi'' detected by ELISA
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***Immunofluorescence
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***Culture in Barbour-Stoenner-Kelly medium for 6 weeks under microaerophilic conditions
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***PCR
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**Treatment and control
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***Amoxycillin and oxytetracycline in the acute phase; prolonged treatment in the chronic phase
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***Tick control and removal
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***Vaccines including whole cell bacterins and recombinant subunit vaccines available for dogs
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===Avian spirochaetosis===
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*Caused by ''Borrelia anserina''
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*Acute, endemic disease of birds in tropical and subtropical regions
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*Chickens, turkeys, pheasants, ducks and geese susceptible
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*Transmitted by soft ticks of the ''Argas'' family, but also via contact with infected material such as blood and tissues
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*Transmitted transovarially and trans-stadially via the tick population
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*Outbreaks during peak tick activity during warm, humid conditions
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*Fever, anaemia and wight loss occurs, with development of paralysis later
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*Immunity is serotype specific
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*Diagnosis using dark-field microscopy of buffy coat smears or immunodluorescence of blood or tissues
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*Giemsa-stained smears and silver impregnation of tissues
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*Isolation of borreliae by inoculation of embryonated eggs or chicks
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*Antibiotic treatment
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*Inactivated vaccines available
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===''Brachyspira'' and ''Serpulina''===
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   −
   
[[Brachyspira hyodysenteriae]]
 
[[Brachyspira hyodysenteriae]]
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