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Actinobacillus pleuropneumoniae (view source)
Revision as of 11:18, 10 May 2010
, 11:18, 10 May 2010Created page with '*Contagious porcine pleuropneumonia especially of pigs under 6 months *Endemic in UK *12 serotypes causing the same disease *Different serotypes in different regions, with seroty…'
*Contagious porcine pleuropneumonia especially of pigs under 6 months
*Endemic in UK
*12 serotypes causing the same disease
*Different serotypes in different regions, with serotypes 3,6 and 8 the most common in the UK
*Pathogenesis and pathogenicity:
**Virulent strains possess capsules which are antiphagocytic and immunogenic
**Fimbriae allow the bacteria to attach to cells of the respiratory tract
**Damaged [[Neutrophils - WikiBlood|neutrophils]] in the lungs produce lytic enzymes
**The sustained inflammatory response causes tissue necrosis
**Lungs consolidated and necrotic with fibrinous pleuisy at post mortem
**Produce three cytotoxins which belong to the repeats-in-structural-toxin (RTX) cytolysin family
**RTX toxins:
***Several peptide repeats within the molecules
***Produced by various Gram-negative bacteria
***Possess four contiguous genes, A, B, C and D
***A is the structural gene; B and D are required for secretion; C allows post-translational activation of the gene product of A into a functional product
***ApxI is a strong haemolysin with cytolytic activity
***ApxII is a weak haemolysin
***ApxIII is a cytotoxin
***Different ''Actinobacillus pleuropneumonia'' serotypes secrete a particular combination of toxins; American serotypes secrete ApxI and II; European serotypes secrete ApxII and III
***Toxins introduce pores into cell membranes
*Clinical signs and epidemiology:
**Acute disease in susceptible herds with high morbidity and mortality (up to 50%)
**In acute outbreaks, pigs may be dyspnoeic, pyrexic or anorexic
**Blood-stained froth surrounding nose and mouth
**Cyanosis
**Pregnant sows abort
**Causes [[Respiratory Bacterial Infections - Pathology#Actinobacillus pleuropneumoniae|pneumonia]] in pigs
**Carrier herds have some immunity, protecting from acute disease, where lesions are often subclinical, and deaths sporadic
**Lung scarring and pleural adhesions in many recovered animals
**Solid immunity develops in recovered animals to all serotypes
**The disease is spread between herds by carrier pigs
*Diagnosis:
**Haemorrhagic consolidation close to the main bronchi and fibrinous pleuritis may be suggestive
**Specimens are cultured on chocolate agar and blood agar in 5-10% carbon dioxide for 2-3 days
**Small colonies surrounded by clear haemolysis
**No growth on MacConkey agar
**Positive CAMP reaction with [[Staphylococcus spp.|''Staphylococcus aureus'']]
**Most strains are NAD-dependent (grow on Heated Blood agar)
**Immunofluorescent- or PCR-based techniques
**The bacteria on the [[Tonsils - Anatomy & Physiology#Palatine|palatine tonsil]] may remain undetected by serological tests and swabbing, and can therefore cause an outbreak in naive pigs
*Treatment:
**Antibiotics depending on the strain of bacteria
**Prophylactic antibiotics for in-contact pigs
*Control:
**Killed and polyvalent bacterin vaccines as well as a subunit vaccine are available
**Improve ventilation, avoid chilling and overcrowding
[[Category:Actinobacillus_species]][[Category:Pig]]
*Endemic in UK
*12 serotypes causing the same disease
*Different serotypes in different regions, with serotypes 3,6 and 8 the most common in the UK
*Pathogenesis and pathogenicity:
**Virulent strains possess capsules which are antiphagocytic and immunogenic
**Fimbriae allow the bacteria to attach to cells of the respiratory tract
**Damaged [[Neutrophils - WikiBlood|neutrophils]] in the lungs produce lytic enzymes
**The sustained inflammatory response causes tissue necrosis
**Lungs consolidated and necrotic with fibrinous pleuisy at post mortem
**Produce three cytotoxins which belong to the repeats-in-structural-toxin (RTX) cytolysin family
**RTX toxins:
***Several peptide repeats within the molecules
***Produced by various Gram-negative bacteria
***Possess four contiguous genes, A, B, C and D
***A is the structural gene; B and D are required for secretion; C allows post-translational activation of the gene product of A into a functional product
***ApxI is a strong haemolysin with cytolytic activity
***ApxII is a weak haemolysin
***ApxIII is a cytotoxin
***Different ''Actinobacillus pleuropneumonia'' serotypes secrete a particular combination of toxins; American serotypes secrete ApxI and II; European serotypes secrete ApxII and III
***Toxins introduce pores into cell membranes
*Clinical signs and epidemiology:
**Acute disease in susceptible herds with high morbidity and mortality (up to 50%)
**In acute outbreaks, pigs may be dyspnoeic, pyrexic or anorexic
**Blood-stained froth surrounding nose and mouth
**Cyanosis
**Pregnant sows abort
**Causes [[Respiratory Bacterial Infections - Pathology#Actinobacillus pleuropneumoniae|pneumonia]] in pigs
**Carrier herds have some immunity, protecting from acute disease, where lesions are often subclinical, and deaths sporadic
**Lung scarring and pleural adhesions in many recovered animals
**Solid immunity develops in recovered animals to all serotypes
**The disease is spread between herds by carrier pigs
*Diagnosis:
**Haemorrhagic consolidation close to the main bronchi and fibrinous pleuritis may be suggestive
**Specimens are cultured on chocolate agar and blood agar in 5-10% carbon dioxide for 2-3 days
**Small colonies surrounded by clear haemolysis
**No growth on MacConkey agar
**Positive CAMP reaction with [[Staphylococcus spp.|''Staphylococcus aureus'']]
**Most strains are NAD-dependent (grow on Heated Blood agar)
**Immunofluorescent- or PCR-based techniques
**The bacteria on the [[Tonsils - Anatomy & Physiology#Palatine|palatine tonsil]] may remain undetected by serological tests and swabbing, and can therefore cause an outbreak in naive pigs
*Treatment:
**Antibiotics depending on the strain of bacteria
**Prophylactic antibiotics for in-contact pigs
*Control:
**Killed and polyvalent bacterin vaccines as well as a subunit vaccine are available
**Improve ventilation, avoid chilling and overcrowding
[[Category:Actinobacillus_species]][[Category:Pig]]