Difference between revisions of "Moraxella bovis"

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#redirect[[Infectious Bovine Keratoconjunctivitis]]
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<big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
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<big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
  
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===Overview===
  
[[Category:Bacteria miscellaneous]] [[Category:Rods]] [[Category:Cocci]] [[Category:Cattle Bacteria]]
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*''Moraxella bovis'' causes infectious bovine keratoconjunctivitis
 +
*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 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

Revision as of 17:40, 26 May 2008

BACK TO INFECTIOUS AGENTS AND PARASITES
BACK TO BACTERIA

Overview

  • Moraxella bovis causes infectious bovine keratoconjunctivitis
  • 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 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