Difference between revisions of "Actinobacillus pleuropneumoniae"

Revision as of 09:51, 25 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

@@ Line 1: / Line 1: @@
-*Contagious porcine pleuropneumonia especially of pigs under 6 months
+*[[Contagious Porcine Pleuropneumonia]] especially of pigs under 6 months
 *Endemic in UK
 *12 serotypes causing the same disease
@@ Line 20: / Line 20: @@
 ***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]]
+[[Category:To_Do_-_Bacteria]]

Difference between revisions of "Actinobacillus pleuropneumoniae"

Revision as of 09:51, 25 June 2010

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