Erysipelothrix rhusiopathiae
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Overview
- Causes erysipelas in pigs and turkeys worldwide
- Arthritis and discospondylitis in pigs as well as cutaneous lesions
- Occasionally causes arthritis in sheep and disease in other animals
- Causes erysipeloid, a localised cellulitis in humans
- Found in porcine tonsils - 50% of pigs are thought to be carriers
- Bacteria excreted in faeces and oronasal secretions
- Survive in soil for less than 35 days
- Present on fish
Characteristics
- Gram-positive, small rod (smooth form) or filamentous (rough form)
- Facultative anaerobe
- Non-motile
- Catalase negative, oxidase negative, coagulase positive
- Grow on nutrient agar; growth enhanced by addition of blood or serum
- Small colonies with incomplete haemolysis in 48 hours
- Hydrogen sulphide formed as black central line in TSI agar
- Growth over wide rangs of temperatures and pH
Identification and diagnosis
- Isolates from acute infections produce smooth colonies; 1.5mm diamteter, convex and circular with even edges
- Isolates from chronic infections produce rough colonies; larger, flat and opaque colonieswith irregular edges
- Biochemical tests
- Serotypying according to a heat-stable peptidoglycan extracted from the cell wall
- Virulence testing in lab animals
- PCR for detection of virulent isolates
Pathogenesis and pathogenicity
- Route of infection: ingestion from pig faeces
- Entry via tonsils, skin or mucous membranes
- Capsule prevents phagocytosis
- Adhere to endothelial cells
- Produce neurominidase which enhances cell penetration
- Septicaemia with vascular damage
- Swelling of endothelial cells, monocyte adherence to vascular walls and hyaline microthrombus formation
- Bacteria localise in synovia of joints and on heart valves during bacteraemia and cause chronic lesions
- Host immune response to persistent bacterial antigens causes long-term damage to the joints
Swine erysipelas
- Carrier pigs act as reservoir of infection
- Organisms excreted in faeces of acutely-affected pigs
- Ingestion of contaminated food and water, or via skin abrasions
- Clinical outcome depends on susceptibility of pigs and virulence of strain
- Pigs susceptible after maternal antibody waned (after 3 months) and before protective immunity acquired (3 years)
- Change in diet, extremes of temperature and fatigue thought to predispose to infection
- Septicaemic form:
- Acute; incubation period 2-3 days
- Pigs found dead, febrile, depressed, recumbent or with stilted gait
- Mortality high
- Pregant sows abort
- Cutaneous form:
- Diamond skin lesions
- Fewer systemic signs, mortality rates lower
- Pigs febrile with small, pink/purple raised areas or extensive diamond-shaped plaques over skin
- Lesions may resolve within a week, or become necrotic and slough
- Arthritis:
- Older pigs, chronic
- Stiffness, lameness, non-weight bearing on affected limbs
- Joint lesions with erosion of articular cartilage, fibrosis and ankylosis
- Strong impact on productivity
- Chronic valvular endocarditis:
- Vegetatic thrombosis of mitral valves
- Asymptomatic or congestive heart failure and sudden death with stress
- Diagnosis:
- Diamond-shaped skin lesions
- Haematology and post mortem, especially liver, spleen, heart valves, synovial tissues
- Slender Gram-positive rods on microscopy of acute lesions; filamentous forms in chronic lesions and smears
- No growth on MacConkey agar
- Colonial characteristics and biochemical tests
- Treatment:
- Penicillin and tetracyclines for acute infections
- Hyperimmune serum
- Control:
- Hygience
- Cull chronic cases
- Isolate affected pigs
- Live attenuated or inactivated vaccines
Turkey erysipelas
- Affects birds of all ages
- Excreted in semen, causing death of turkey hens 4-5 days after AI
- Septicaemia
- High mortality
- Dark, swollen snoods
- Enlarged friable liver and spleen on post mortem
- Arthritis and vegetative endocarditis and emaciation with chronic infections
- Inactivated vaccine
Sheep infections
- Non-suppurative polyarthritis of lambs from contamination of navel or tail-docking/castration wounds
- Cellulitis and laminitis in older lambs and ewes causing post-dipping lameness - entry through skin abrasions in hoof from contaminated dip
- Valvular endocarditis and pneumonia in ewes reported
Human erysipeloid
- Infection through skin wounds from fish and poultry
- Localised cellulitis
- Occasional joint and heart disease after haematogenous spread if untreated