151. Infectious keratoconjuctivitis of cattle.

Question 1

Aetiology?

Answer 1

Aetiology:

• Bacterium species:
• M. lacunata,
• M. catarrhalis,
• M. bovis,
• M. ovis (M = Moraxella)
• Mucous membranes, conjunctiva, upper resp tract (sinuses)
• Fastidious bacteria: replicate only on mucous membrane on infected host
• Facultative pathogen
• Resistance low: for short time when they are shed with tears
• M. lacunata: Can cause conjunctivitis in humans ʹ but importance is going down!
• M. catarrhalis: diseases of upper resp tract & middle ear infection of kids
• Diseases
• Infectious keratoconjunctivitis of cattle: more frequent, more severe, worldwide
• Infectious keratoconjunctivitis of Ov, cap: more sporadic, milder
• Infectious keratoconjunctivitis of Wild - rare

Question 2

Infectious keratoconjunctivits Occurence?

Answer 2

Infectious Keratoconjunctivitis (pink eye, infectious ophthalmia)

Occurrence:

• Susceptible: M bovis Æ Cattle, M ovis Æ Sheep
• worldwide, mainly warm climate, summer
• animals on pasture with no shade, sometimes mass occurrence

Question 3

Aetiology of infectious keraconjuctivitis?

Answer 3

Aetiology:

• M. bovis: cattle, growers (>6m old)
• 7 serotypes based on fimbria antigens
• Virulence factors:
• Fimbria (adhesins): attach to epithelial cells of conjunctiva
• Cytotoxin (haemolysin/cytolysin): increase the permeability of other cells
• Extra cellular enzymes (protease, lipase, phospholipase etc.)
• Protease responsible for the severe lesions
• o Others have a role in the histological lesions
• Low resistance
• M. ovis:
• young calves (<4m old ʹ similar CS but maybe milder),
• sheep (~>2m, all ages?)
• Virulence factors: fimbria, haemolysin
• Cannot produce EC enzymes (lesions not as severe as M. bovis)

Question 4

Epidemiology of infectious keratoconjuctivitis?

Answer 4

Epidemiology

• Rapid spreading (can survive in tears for limited time)
• Predisposing effects:
• Environment: sunlight, dust, irritating agents/chemicals (NH3), shipping, absence of shadow,
• stress
• Arthropods: flies - transmit the infection, not real vectors (not replicating in flies), contact with the
• tears of the cows and fly to the next animal, fly survival = 2 days
• Infectious:
• Mycoplasma,
• Chlamydia, IBR, adenoviruses

Question 5

Pathogenesis of infectious keratoconjuctivitis?

Answer 5

Pathogenesis-

• Limited to the eyes (not generalised)
• Infection-> colonise MM of conjunctiva- replicate(Producing proteases and toxin)
• Adherence to the epithelium(fimbria)
• Proteases- destroy the affected area(inflammation) -> very itchy-> rub eye = way of transmission)
• Toxin: pore forming toxin(cytoplasm membrane)
• Conjuctivitis- most important cs –> cornea–> more severe
• Heals sometimes do not die
• Rubbing eye causes wounds = place of entry for other purulent bacteria –> more severe inflammation of eyes (Blindness)

Question 6

Clinical signs of infectious keratoconjunctivitis?

Answer 6

Clinical signs

• Conjunctiva Hyperemia (Pink eye)
• Ocular discharge, increased lacrimation, eyelid oedema
• Photophobia, blepharospasm
• Corneal opacity (lesions on the centre of the cornea), recovering (BVs come from the periphery)
• Itching,
• Complications: corneal ulcer, purulent inflammation
• Sheep: milder

Question 7

Diagnosis, differential diagnosis, treatment and prevention of infectious keratoconjunctivits?

Answer 7

Diagnosis

• Epidemiology , clinical signs
• Laboratory diagnosis:
• Detection of the agent: smear (staining, M. bovis: always double rods, M. ovis: 2 cocci),
• bacterium isolation
• Detection of other agents ʹ can complicate other diseases

Differential diagnosis:

1. BVD,
2. IBR,
3. malignant catarrhal fever,
4. mycoplasmosis,
5. chlamydiosis

Treatment

• Elimination of the predisposing factors ʹ improve efficacy of treatment
• Rest (reduced light, no wind, no dust, no flies), insect control
• Antibiotics: local (reach higher conc, ointment better than drops), parenteral

Prevention

• Preventing predisposing factors
• Vaccines: inactivated (fimbria),
• vaccination of 2-4 months old calves,
• 2x; prevent infection for the season