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| − | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
| + | #REDIRECT[[:Category:Actinobacillus species]] |
| − | <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
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| − | ===Overview===
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| − | *Mainly pathogens of farm animals
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| − | *Commensals of mucosa of upper respiratory tract and oral cavity
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| − | *Cannot survive long in the environment, therefore carrier animals are important in their transmission
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| − | *Cause [[General Pathology - Chronic Inflammation#Granulomatous Inflammation|granulomatous inflammation]]
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| − | ===''Actinobacillus'' characteristics===
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| − | *Small Gram negative coccobacilli
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| − | *Oxidase negative
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| − | *Do not grow on MacConkey
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| − | *Non-motile
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| − | *Facultative anaerobes which ferment carbohydrates to produce acid
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| − | ===''Actinobacillus lignieresii''===
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| − | *Pathogenesis and pathogenicity:
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| − | **Commensal in the mouth and intestinal tract of cattle and sheep
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| − | **Penetrates damaged mucosa to cause chronic granulomatous inflammation of soft tissues, a condition known as Actinobacillosis
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| − | **Enodogenous, sporadic infection
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| − | **Lesions in the tongue, cheek, lips and sometimes in the lower gut and lungs from aspiration
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| − | **Often spreads from the site of infection to lymphatics, and may cause pyogranulomatous lymphadenitis
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| − | **[[Muscles - inflammatory#Wooden tongue|Myositis]] and formation of fibrous tissue in the lesions lead to hardening of the tissue, hence the condition is known as 'wooden tongue' in cattle
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| − | **In sheep abscesses with thick walls are produced
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| − | **Feeding is impaired, causing loss of condition
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| − | **Infection in the oesophageal groove can cause tympany and enlargement of the retropharyngeal lymph node, causing difficulty in swallowing and breathing
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| − | **[[Bacterial skin infections#Bacterial granulomatous dermatitis|Cutaneous lesions]] in cattle and sheep
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| − | **Contamination of the environment via ulcerating lesions
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| − | *Diagnosis:
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| − | **Induration of tongue
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| − | **Tissue sections may demonstrate pyogranulomatous foci containing club colonies
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| − | **Gram negative rods may be present in smears from exudates
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| − | **Cultures on blood agar and MacConkey agar, incubated for 24-72 hours
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| − | **Blood agar: small, sticky, non-haemolytic clonies
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| − | **MacConkey agar: slow lactose fermentation
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| − | *Treatment:
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| − | **Sodium iodide parenterally, or potassium iodide orally
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| − | **Potentiated sulphonamides or a penicillin/streptomycin combination
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| − | **Rough feed should be avoided
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| − | ===''Actinobacillus pleuropneumoniae''===
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| − | *Contagious porcine pleuropneumonia especially of pigs under 6 months
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| − | *Endemic in UK
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| − | *12 serotypes causing the same disease
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| − | *Different serotypes in different regions, with serotypes 3,6 and 8 the most common in the UK
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| − | *Pathogenesis and pathogenicity:
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| − | **Virulent strains possess capsules which are antiphagocytic and immunogenic
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| − | **Fimbriae allow the bacteria to attach to cells of the respiratory tract
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| − | **Damaged neutrophils in the lungs produce lytic enzymes
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| − | **The sustained inflammatory response causes tissue necrosis
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| − | **Lungs consolidated and necrotic with fibrinous pleuisy at post mortem
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| − | **Produce three cytotoxins which belong to the repeats-in-structural-toxin (RTX) cytolysin family
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| − | **RTX toxins:
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| − | ***Several peptide repeats within the molecules
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| − | ***Produced by various Gram-negative bacteria
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| − | ***Possess four contiguous genes, A, B, C and D
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| − | ***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
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| − | ***ApxI is a strong haemolysin with cytolytic activity
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| − | ***ApxII is a weak haemolysin
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| − | ***ApxIII is a cytotoxin
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| − | ***Different ''Actinobacillus pleuropneumonia'' serotypes secrete a particular combination of toxins; American serotypes secrete ApxI and II; European serotypes secrete ApxII and III
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| − | ***Toxins introduce pores into cell membranes
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| − | *Clinical signs and epidemiology:
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| − | **Acute disease in susceptible herds with high morbidity and mortality (up to 50%)
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| − | **In acute outbreaks, pigs may be dyspnoeic, pyrexic or anorexic
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| − | **Blood-stained froth surrounding nose and mouth
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| − | **Cyanosis
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| − | **Pregnant sows abort
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| − | **Causes [[Bacterial infections#Actinobacillus pleuropneumoniae|pneumonia]] in pigs
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| − | **Carrier herds have some immunity, protecting from acute disease, where lesions are often subclinical, and deaths sporadic
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| − | **Lung scarring and pleural adhesions in many recovered animals
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| − | **Solid immunity develops in recovered animals to all serotypes
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| − | **The disease is spread between herds by carrier pigs
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| − | *Diagnosis:
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| − | **Haemorrhagic consolidation close to the main bronchi and fibrinous pleuritis may be suggestive
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| − | **Specimens are cultured on chocolate agar and blood agar in 5-10% carbon dioxide for 2-3 days
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| − | **Small colonies surrounded by clear haemolysis
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| − | **No growth on MacConkey agar
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| − | **Positive CAMP reaction with [[Staphylococcus spp.|''Staphylococcus aureus'']]
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| − | **Most strains are NAD-dependent (grow on Heated Blood agar)
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| − | **Immunofluorescent- or PCR-based techniques
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| − | **The bacteria on the palatine tonsil may remain undetected by serological tests and swabbing, and can therefore cause an outbreak in naive pigs
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| − | *Treatment:
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| − | **Antibiotics depending on the strain of bacteria
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| − | **Prophylactic antibiotics for in-contact pigs
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| − | *Control:
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| − | **Killed and polyvalent bacterin vaccines as well as a subunit vaccine are available
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| − | **Improve ventilation, avoid chilling and overcrowding
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| − | ===''Actinobacillus equuli''===
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| − | *Commensal of the equine intestinal and reproductive tract
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| − | *Pathogenesis and clinical signs:
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| − | **Foals infected ''in utero'' or or after birth via the umbilicus
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| − | **Infection at birth causes severe enteritis and septicaemia within 24 hours, known as sleepy foal disease
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| − | **Foals become pyrexic and recumbent
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| − | **Death usually occurs within 1-2 days
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| − | **In foals that survive neonatal infection the condition progresses to cause joint infections and purulent nephritis, enteritis or pneumonia
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| − | **''A. equuli'' in [[Joints - inflammatory#In Horses|arthritis of horses]]
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| − | **Abortion, septicaemia and [[Peritoneal cavity - inflammatory#In horses|peritonitis in horses]]
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| − | *Diagnosis:
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| − | **Specimens cultured on blood agar and MacConkey agar and incubated aerobically for 1-3 days
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| − | **Sticky colonies with variable haemolysis on blood agar
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| − | **Lactose-fermenting colonies on MacConkey agar
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| − | *Treatment and control:
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| − | **Antimicrobials ineffective unless early in course of disease
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| − | **Blood trasfusion and administration of colostrum
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| − | **Good hygiene
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| − | **Consider prophylactic antibiotics for new-born foals
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| − | **Bacteria susceptible to streptomycin, tetracyclines and ampicillin
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| − | *In other animals:
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| − | **Septicaemia in piglets
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| − | **Arthritis and enteritis in pigs
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| − | **Enteritis in calves
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| − | **RTX group cytotoxin present
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| − | ===''Actinobacillus suis''===
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| − | *May be present in upper respiratory tract of sows
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| − | *Pathogenicity and clinical signs:
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| − | **Infection of piglets via aerosol or possibly skin abrasions
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| − | **Fatal septicaemia in piglets 1-8 weeks old
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| − | **Mortality up to 50% in some litters
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| − | **Fever, respiratory distress, prostration and paddling of forelimbs seen in piglets
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| − | **Petechial and ecchymotic haemorrhages in many organs
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| − | **Interstitial pneumonia, pleuritis, meningoencephalitis, myocarditis and arthritis
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| − | **Causes abscesses in joints and lungs of older pigs
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| − | **Carried in the nasopharynx of pigs and nose of horses
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| − | **Carriage may confer immunity to the more severe pleuropneumonia
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| − | *Diagnosis:
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| − | **Specimens cultured on blood agar and MacConkey agar for 1-3 days
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| − | **Sticky haemolytic colonies
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| − | **Pink, lactose-fermenting colonies on MacConkey agar
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| − | *Treatment and control:
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| − | **Bacteria usually susceptible to ampicillin, carbenicillin, potentiated sulphonamides and tetracyclines
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| − | **Disinfect contaminated pens
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| − | *Other animals:
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| − | **Septicaemia and pneumonia in foals
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| − | **Pneumonia in pigs and horses
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| − | ===''Actinobacillus seminis''===
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| − | *Epididymitis in young rams (4-8 months)
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| − | *Polyarthritis in lambs
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| − | *Organism found in prepuce
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| − | *Opportunistic infection causing abscesses in epididymides
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| − | *May be purulent discharge onto scrotal skin
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| − | *Specimens cultured on blood agar and incubated aerobically for 1-3 days produce pin-point haemolytic colonies which are catalase-positive; no growth on MacConkey agar
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| − | ===''Actinobacillus actinomycetemcomitans''===
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| − | *Epididymitis in rams
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