Difference between revisions of "Actinobacillus pleuropneumoniae"
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− | + | *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|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 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]] | |
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− | [[Category:Actinobacillus_species]] [[Category: |
Revision as of 12:27, 12 June 2010
- 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 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 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 aureus
- Most strains are NAD-dependent (grow on Heated Blood agar)
- Immunofluorescent- or PCR-based techniques
- The bacteria on the 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