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Infectious Bovine Keratoconjunctivitis (view source)
Revision as of 11:35, 28 July 2011
, 11:35, 28 July 2011no edit summary
|species = ''M. bovis''
|species = ''M. bovis''
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Also Known As – '''''IBK - New Forest Eye – New Forest Disease - Pinkeye – Pink-eye - Infectious Opthalmia – Blight'''''
Caused By – ''Moraxella bovis''
==Introduction==
Infectious bovine keratoconjunctivitis or New forest eye disease is an '''ocular disease of cattle caused by the gram negative, β-haemolytic, aerobic rod shaped [[Bacteria|bacterium]], ''Moraxella bovis'' '''. The bacterium is non-motile and occurs in pairs.
This disease is the '''most common and important ocular disease seen in cattle worldwide'''.
This disease is not zoonotic.
==Distribution==
IBK is seen worldwide but mainly in areas with '''high temperature climates''' and thus is '''widespread in Asia, Africa and all American continents'''. It is also seen in parts of '''Europe and the UK'''. In seasonal countries, disease is most prevalent in the '''summer months and is usually seen in young animals'''. During the warmer months, fly numbers are higher and intense sunlight and dust predispose the eye to infection.
Disease is transmitted by '''[[Biting Flies|biting flies]], including ''[[Haematobia irritans]], [[Musca domestica]], [[Stomoxys calcitrans]]'' and ''[[Musca autumnalis]]'' '''. It can also be transmitted by infected animals, via contact with '''mucous membranes and their secretions''', and also by asymptomatic carrier individuals. Carrier animals often carry avirulent, non-pathogenic strains of ''M.bovis.''
==Signalment==
'''Bos taurus and Bos indicus cattle''' can be affected; disease is not documented in any other species.
Young cattle are often, but not exclusively affected.
A similar disease is seen in horses, caused by a different ''Moraxella'' species.
==Pathogenesis==
''M. bovis'' '''invades the lacrimal and tarsal glands of the eye''', causing '''keratitis, opacity, uveitis, aqueous flare and corneal ulcers'''.
The bacterium '''adheres''' to the cells via its '''fimbriae and pili proteins''', and produces '''β-haemolysin toxins which lyse the corneal epithelial cells'''.<ref> Billson, F. M., Harbour, C., Michalski, w. P., Tennent, J. M., Egerton, J. R., Hodgson, J. L (2000) '''Characterisation of haemolysin of Moraxella bovis using a hemolysin-neutralising monoclonal antibody'''. Inf. and Immun., 3469-3474</ref> M. bovis also secretes cytotoxic toxin and pathogenic fibrinolysin, phosphatase, hyaluronidase and aminopeptidases.
The bacterial '''membrane proteins and LPS are also pathogenic'''.<ref>Prieto, C. I., Aguilar, O. M., Yantorno, O. M. (1999) '''Analyses of lipopolysaccharides, outer membrane proteins and DNA fingerprints reveal intraspecies diversity in Moraxella bovis isolated in Argentina'''. Veterinary Microbiology, 70(3/4):213-223; 36</ref>
==Clinical Signs==
Inflammation of the cornea caused by the bacterium and its toxins causes '''pain, blepharospasm, lacrimation, photophobia and conjunctivitis. Ocular discharge''' begins serous and may become mucopurulent. '''Corneal ulcers''' may be visible on physical examination. Affected animals are often also '''inappetant and may lose weight and productivity.'''
''Severe or untreated cases can lead to panophthalmitis and permanent blindness.'''
Age related immunity often develops after exposure when young.
==Diagnosis==
Pathology remains confined to the eye and does not reach the bloodstream. Diagnosis is usually based on clinical signs.
On clinical examination (and necropsy if incidentally found), '''early disease is detectable as a raised area of cloudiness''' in the cornea<ref>Bedford, P. G. C (1992) '''Ocular diseases'''. Bovine medicine: diseases and husbandry, ''Wiley-Blackwell, Oxford'', pp712-721; 27</ref> indicating keratitis. This then spreads and '''corneal oedema develops giving the eye a blue tint'''. Conjunctivitis is evident by '''oedema, erythema and vascular congestion of the scleral vessels'''. Corneal ulcers may be visible on gross examination and are more obvious with administration of '''fluoroscein dye'''. They may be superficial or deep and may leave stromal scars behind after healing.
Season and history of infection and presence of flies will raise suspicion of IBK before an animal is examined.
Lacrimal swabs can be taken and the bacterium can then be '''cultured on media impregnated with blood or serum''' where it forms small, round, shiny, friable colonies. It will not grow on MacConkey agar. '''[[Fluorescent antibody testing]] (FAT)''' is also available for identification. The bacterium is also visible on smears of lacrimal secretions.
==Treatment==
'''Sub-conjunctival injections of appropriate antibiotics such as cloxacillin''' are most effective, but treatment can also be given '''systemically, e.g. oxytetracycline, cephalonium and penicillin-streptomycin''' combinations. Early acute cases may respond to '''ophthalmic ointments such as those containing oxytetracycline and penicillin-streptomycin'''. Withdrawal periods must be adhered to, so selecting a drug licensed for the preferred method of administration is advised.
'''Anti-inflammatory therapy''' may also improve demeanours during recovery.
Recovery time ranges from days to months depending on the severity of infection and ulcer formation.
If possible, animals should be housed indoors during treatment so that flies can be controlled and irritation minimised.
Severe cases may require '''surgery such as temporary third eyelid closure or conjunctival pedicle grafts'' to facilitate ulcer healing.
==Control==
Eradiation is not possible due to the '''ubiquitous''' nature of ''M. bovis''. Fly control is valuable but rarely practical. '''Early detection and treatment''' of affected individuals may restrict spread of an outbreak.
{{Learning
|flashcards = [[Infectious Bovine Keratoconjunctivitis Flashcards]]
}}
==References==
<references/>
Animal Health & Production Compendium, '''Moraxella bovis datasheet''', accessed 28/07/2011 @ http://www.cabi.org/ahpc/
Animal Health & Production Compendium, '''Infectious Bovine Keratoconjunctivitis datasheet''', accessed 28/07/2011 @ http://www.cabi.org/ahpc/
Haskell, S (2008) '''Blackwell’s Five-Minute Veterinary Consult: Ruminant'''. ''Wiley-Blackwell, Oxford''
Merck Veterinary Manual, '''Infectious Keratoconjunctivitis''', accessed online 24/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/30500.htm
[[Category:To Do - CABI review]]
[[Category:Bacteria miscellaneous]] [[Category:Rods]] [[Category:Cocci]] [[Category:Cattle Bacteria]] [[Category:Neurological Diseases - Cattle]]