Difference between revisions of "Moraxella bovis"

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#redirect[[Infectious Bovine Keratoconjunctivitis]]
  
===Overview===
 
  
*''Moraxella bovis'' causes infectious bovine keratoconjunctivitis
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[[Category:Bacteria miscellaneous]] [[Category:Rods]] [[Category:Cocci]] [[Category:Cattle Bacteria]]
*Found on mucous membranes of carrier cattle
 
*Susceptible to desiccation therefore short survival in environment
 
*Flies act as vectors, in which the bacteria can survive 72 hours
 
*Other species non-pathogenic
 
 
 
 
 
===Characteristics===
 
 
 
*Short, plump Gram negative rods or cocci occuring in pairs
 
*Non-motile
 
*Aerobic
 
*Catalase positive, oxidase postitive
 
*Unable to utilise sugars
 
*No growth on MacConkey agar
 
*Growth enhanced by addition of blood or serum to media
 
 
 
 
 
===Pathogenesis and pathogenicity===
 
 
 
*Virulent strains have fimbriae, are haemolytic and grow into agar
 
*Fimbriae allow adherence to the cornea
 
*Q fimbriae are specific for colonisation; I fimbriae allow local persistence of infection
 
*Fimbrial antigens stimulate immunity
 
*Haemolysin, fibrinolysin, phosphatase, hyaluronidase and aminopeptidase as well as LPS contribute to virulence
 
*Haemolysin damages neutrophil membranes; release of hydrolytic enzymes from these [[Neutrophils|neutrophils]] damages the corneal surface
 
*Isolates from carrier animals often avirulent, and are non-haemolytic and have no fimbriae; reversion to virulence can occur
 
 
 
 
 
===Clnical infections===
 
 
 
*Infectious bovine keratoconjunctivitis, or pink-eye/New Forest disease is an ocular disease of cattle
 
*Highly contagious infection of superficial tissues of eye
 
*Affects animals under 2 years old
 
*Decreased weight gain in beef cattle, decreased milk production in dairy herds
 
*Age-related immunity due to previous exposure
 
*Antibodies against haemolysin neutralise different strains, whereas antibodies to fimbriae are strain-specific
 
*Asymptomatic carrier animals harbour the bacteria in the nasolacrimal ducts, nasopharynx and vagina
 
*Transmission by direct contact, aerosol and via flies
 
*Clinical signs: blepharospasm, conjunctivitis, lacrimation
 
*Keratitis and corneal ulceration, opacity and abscessation may lead to panophthalmitis and permanent blindness
 
*Stromal oedema; coning of cornea
 
*Cornea may heal or undergo permanent scarring
 
 
 
 
 
===Diagnosis===
 
 
 
*Swabs of lacrimal secretions
 
*Fluorescent antibody test demonstrate presence of ''M. bovis''
 
*Culture on blood agar; colonies are round, small, shiny and friable
 
*Virulent strains surrounded by complete haemolysis and are embedded in the agar
 
*No growth on MacConkey
 
*Autoagglutination in saline
 
*Short Gram negative rods on smears
 
*7 serotypes based on fimbriae
 
 
 
 
 
===Treatment and control===
 
 
 
*Subconjunctival or topical antimicrobials
 
*Isolate animals
 
*Reduce mechanical irritation such as dust, grass, grass seeds
 
*Insect control
 
*Control concurrent infections
 
*Prophylactic oxytetracycline for animals at risk
 
*Vitamin A supplementation
 
[[Category:Bacteria miscellaneous]][[Category:Rods]][[Category:Cocci]][[Category:Cattle]]
 
[[Category:To_Do_-_Bacteria]]
 

Latest revision as of 22:55, 28 July 2011