Difference between revisions of "Moraxella bovis"
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− | + | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big> | |
+ | <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big> | ||
+ | ===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 |
Revision as of 17:40, 26 May 2008
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