Spirochaetes
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- Created by: fionnualamaire94
- Created on: 01-12-16 10:26
Leptospira
- thin spiral organisms
- stain poorly, better visualised by dark field microscopy
- persist in humid environments (water-saturated soil, pastures)
- host-adapted serovars - leptospires infect host and are not eliminated, induce asymptomatic or mild sometimes chronic disease, host becomes a reservoir for disease almost indefinitely
- non host-adapted serovars - leptospires infect host and can cause acute disease, not maintained in the host
- disease can be acute, sub-acute, chronic or asymptomatic
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Clinical signs leptospira
- Cattle - Leptospira hardjo - may cause sudden drop in milk production 'milk drop syndrome', abortions, birth of weak calves or infertility
- Pigs - commonly infected with Leptospira bratislava in UK, causes reproductive disease
- Dogs - Leptospira canicola or Leptospira icterohaemorrhagiae - kidney failure or liver disease
- Rats - reservoir of infection for Leptospira icterohaemorrhagiae
- Horses - can be found positive for bratislava and icterohaemorrhagiae
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Leptospira pathogenesis
- Entry - through mucous membranes or damages skin via contact with urine or contaminated water, milk, genital secretions
- Spread - mainly haematogenous
- Localisation and proliferation - in lumen of proximal convoluted tubules in kidney, liver, spleen and occasionally brain in sheep and goats. penetration and multiplication in the foetus can lead to abortion
- Damage - of vascular endothelium, interstitial nephritis, production of haemolysin
- Haemorrhages, haemolysis with haemoglobinuria
- may be asymptomatic - shedding
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Leptospira infection as zoonosis
- first human lectospiral disease to be described was known as Weil's disease - febrile illness characterised by jaundice, haemorrhages, and involvement of the kidney - caused by L. icterohaemorrhagiae - transmitted to man by infected rats
- Leptospira serovars - associated with prevalence of infection with the animals with which people have contact
- Leptospiral infection in humans in the UK are mainly L. hardjo (cattle), L. icterohaemorrhagiae (rats, dogs) - about 50 cases per year in UK
- bacteria enter body through cuts/blisters in the skin and through mucous membranes - mouth, conjunctiva, nose
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Brucella
- gram -ve coocobacilli
- intracellular pathogens - persist very well in macrophages
- B. melitensis isolated in 1887 - Bruce from spleens of British soldiers dying in Malta from disease known as Malta fever - 1904 cultured from milk and urine of sheep and goats
- B. abortus isolated in Denmark in 1897 from cattle suffering from infectious abortion - Bang's disease
- B. suis cultured in US in 1914 from foetus of a prematurely delivered sow
- transmitted by ingestion, penetration of skin and conjunctiva
- organusms reach local lymph nodes and reach target organs via blood stream
- main diseases
- abortion
- orchitis and epididymitis
- synovitis and arthritis
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Brucellosis in humans
- Acquired - via raw milk, fresh cheese, handling of infected animals, exposure to contaminated aerosols
- Clinical forms
- asymptomatic
- mild - tiredness, anorexia, muscle pains
- acute - high temperature, hepato-splenomegaly, sweating, arthralgia, muscular pains, weight loss, jaundice, malaise
- chronic-relapsing - same as above but milder symptoms
- complications - epididymitis, orchitis, arthritis
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Dermatophilus congolensis
- first described by Sleghem in cattle in Belgian Congo as contagious dermatitis
- Transmission occurs via - contact, ticks and biting flies
- disease affects - areas vulnerable to abrasion and eposed to wetting (back, muzzle, feet)
- areas infested by arthropods (axilla, ventral trunk, udder)
- predisposing factors
- rainfall and humidity - water can dilute inhibitory substances in skin, facilitate transport of spores from one area to another
- prescence of ticks, flies and biting flies - carry organism, local inflammation - predispose to skin site
- mechanical injuries - shearing, barbed fences, spines/branches
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Dermatophilus congolensis clinical signs
- Cattle - small moist papules which become covered by progressively thickr hard crust and the hair appears as a paintbrush
- Sheep - animals often appear normal with evident lesions only on the ears and muzzle, careful examination reveals papules with moist exudate and crust, wool fibres become matted together with exudate
- Donkeys, Horses, Mules - areas of crust with localised tufts of matted hair
- Man - pustules on hands and feet and scabs
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Erysipelothrix rhusiopathiae
- gram +ve bacillus
- recovered from sewage, soil, slurry from pig farms, faeces and tonsils of normal pigs, surface slime of fresh fish, numerous species of mammals and birds
- infection is acquired mainly by oral route
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Erysipelothrix rhusiopathiae disease (1)
Pigs
- acute septicaemic form
- fever, anorexia depression, reluctance to walk, skin lesions usually present
- uticarial form - diamond skin disease
- usually accompanied by fever and signs of systemic illness
- vegetative endocarditis
- fibrin deposition and connective tissue proliferation
- arthritis and synovitis, erosion of joints
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Erysipelothrix rhusiopathiae disease (2)
- Birds (turkey and geese)
- acute septicaemia
- vegetative endocarditis
- arthritis
- Sheep
- polyarthritis in lambs - non suppurative polyarthritis with minor swelling of affected joints
- post-dipping lameness - infection occurs through skin abrasions
- Humans
- erysipeloid (infection of skin and subcut tissue) - occupational hazard in animal and fish handlers, septicaemia, endocarditis and arthritis are rare complications
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Listeria
- gram +ve rods
- can grow between 4C and 45C - optimal 30-37C
- widespread in the environment and in numerous animal species, poor silage with pH >5.5 is a common source of infection
- transmission mainly via oral route, penetration through damaged mucosal surfaces can occur
- L. monocytogenes and L. ivanovii two principal pathogenic species for animals and humans
- mainly in cattle and sheep - 2007 - VLA recorded 45 cases ain cattle and 87 in sheep/goats
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Listeria - disease
- L. monocytogenes
- visceral (septicaemic) listeriosis, necrotic foci in liver and other abdominal organs - young animals of many species, can be birds
- neural listeriosis - circling disease - microabscesses in brain-stem and perivascular cuffing - sheep/goats/cattle sometimes other species
- abortion - sheep/goats/cattle
- iritis, with or without other signs, often associated with feeding big-bale silage - cattle
- L. ivanovii
- abortion - sheep and cattle
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Listeriosis in humans
- last decade - average of 180 cases reported anually
- individuals with impaired cell-mediated immunity and elderly people are most vulnerable
- infection is acquired by ingestion of raw vegetables, milk, fresh cheese, sliced meat, sandwiches, butter
- human infection usually involves
- bacteraemia - especially in older people
- meningitis
- abortion, stillbirth or premature birth
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