FAC23: Farm Animal Ophthalmology and Bovine Skin Diseases Flashcards
What is another name of Infectious Bovine Keratoconjunctivitis?
IBKC, NEw Forest Eye, pink eye
Describe what the cornea looks like in a cow with IBKC.
Central white/cloudy raised lesion
Oedema
After about 6 days there will be vascularisation
How do you treat IBKC?
Long-acting antibiotics. Treat both eyes (but the affected one last)
- Topical - cloxacillin
- Subconjunctival injections - Penicillin
- Systemic - oxytetracycline or florfenicol
How do you control against IBKC?
Reduced predisposing factors
- Fly control
- Adequate headspace at feeders
- Control dust/long vegetation
- Quarantine replacement animals
In an outbreak
- Isolate affected cattle
- Mass treatment
What is another name of listerial uveitis?
Silage eye, ophthalmitis of cattle (and sheep)
What is the associated cause of listerial uveitis?
Listeria monocytogenes
Big bale silage
Describe what the cornea looks like in a cow with listerial uveitis.
Bluish white corneal opacity spreading centrally
White focal aggregations of fibrin
How do you treat listerial uveitis?
If untreated, this painful condition may resolve in 2-3 weeks
Sub-conjunctival injection of penicillin and dexamethasone
What tissues are affected by ocular squamous cell carcinoma?
Non-pigmeneted scleral, conjunctival palpebral tissues
Which breed is most often affected by ocular squamous cell carcinoma?
>5 year old Herefrods
What is the cause of ocular squamous cell carcinoma?
Long-term sunlight exposure
What does the eye look like in a cow with ocular squamous cell carcinoma?
There are conjunctival plaques with or without palpebral hyperkeratosis
How do you treat ocular squamous cell carcinoma?
Surgical removal
- Excision
- Removal of 3rd eyelid
- Enucleation
What disease has both eye and respiratory clinical signs?
Infectious bovine rhinotracheitis
What cattle are susceptible to vitamin A deficiency?
Housed animals fed straw, cereals, sugar beet pulp that are low in VitA
Pastured animals after a severe drought
What is the cause of primary vitamin A deficiency?
Poor status in dam
Not enough colostrum
Fast growing calves
Low supply in feed
What is the cause of secondary vitamin A deficiency?
Low vitamins C/E
High phosphate
Chronic liver/intestinal disease
What are the ocular signs of vitamin A deficiency?
Blindness with bone growth in orbit
Night blindness
Besides ocular signs, what are the other signs of vitamin A deficiency?
Congenital: Convulsions, syncope, ventral neck flexion
Growing calf: As above plus ataxia, bran-like scales in coat
Adult: Reproductive failure
How do you confirm a vitamin A deficiency diagnosis?
Plasma Vit A levels and CSF pressure
How do you treat vitamin A deficiency?
Vit A injection
Which age of sheep is most affected by ovine infectious keratoconjunctivitis?
More severe in ewes than lambs
What are the causes of IKC?
Mycoplasma conjunctivae, chlamydia psittaci, Staphylococcus aureus, E. coli, Branhamella ovis
How do you treat IKC?
Ewes
- Single IM injection of oxytet
- Separated
Lambs
- Not always necessary
- Topical chlortetracycline
How do you prevent and control of IKC?
Adequate space in trough in pens
What is the cause of bright blindness?
Prolonged ingestion of bracken
How do you treat congenital entropion?
Sub-conjunctival injection of antibiotic (penicillin)
Application of michel clips - vertical fold of skin
Name some non-ophthalmic causes of blepharitis.
Viral
- Orf
- Bluetongue
Bacterial
- Dermatophilus
- Actinobacillus
Fungal
- Dermatophytosis
Parasitic
- Psoroptes
- Chorioptes
What is the causative agent of dermatophytosis?
Ringworm
- Trichophyton verrucosum
- T. Mentagrophyttes
Describe ringworm lesions.
Non-pruritic, alopecic lesions that have raised, grey/white powdery surface
Often circular or oval
Describe the pathogenesis of ringworm
- Infection of keratin of hair and skin
- Enzymes attack keratin of actively growing hair
- Hair breaks off
- Inflammatory reaction (often mild)
How do you treat/control for ringworm?
Disease is self-limiting (often 1-4 months) so any treatment just reduces the duration of the disease
Topical: Imaverol
Vaccination: Ringvac (prophylaxis or double dose for treatment)
When are biting and sucking lice most common on cows?
Cold months when animals are housed or in close contact with each other
How do you treat for biting and sucking lice?
Pyrethroid pour-ons or endectocides when animals are at housing
What are the species of mites that cause mange?
Sarcoptes scabiei, Psoroptes ovis, Chorioptes bovis, Demodex
What is the difference between chorioptic mange and sarcoptic mange?
Chorioptic mange is a surface mite, life cycle of 2-3 weeks, and is only transmitted by direct contact
Sarcoptic mange (scabies) is a burrowing mite, life cycle of 10-17 days, and transmitted by direct contact or fomites
How do you treat mites?
Ivermectin pour-on
Permethrin pour-on (not for Psorptes)
Endectocide injection (does not eliminate Chorioptes)
What causes viral papillomatosis?
Bovine papillomavirus
How do you treat papillomatosis?
Uncomplicated cases - no treatment
Otherwise surgical removal/debulking, cryosurgery
What are the primary causes of photo-sensitisation?
Plant origin (St. John’s Wort)
Defective metabolism
What are the secondary causes of photo-sensitisation?
Liver disease
Failure to metabolise phylloerythrin (chlorophyll breakdown product)
Builds up in circulation
What plant causes contact photo-sensitisation?
Giant hogweed sap
How do you treat photo-sensitisation?
House out of sun
Antibiotics for secondary infection
How do you control against photo-sensitisation?
Control liver disease (fluke, ragwort, bog asphodel) and avoid toxic plants
What is fly strike?
Larval infestation of soiled skin, especially in warm damp conditions
How do you treat maggot wounds?
- Manually remove as many maggots as possible
- Clean wound
- Topical application of injectable ivermectin
- Fly repellent around wound
Describe the pathogenesis of warble fly.
- Adults lay eggs on the skin
- Larvae hatch in 4 days and burrow into the skin to overwinter in muscle
- SubQ nodules and cysts form along backs of cattle in spring
- Larvae burst out and pupate to adults in the soil.
How do you control against flies?
Pyrethroid ear tags
Hygiene
- Dry manure
- Reduce feed spoilage
- Reduce moisture
- Fly Traps
- Chemical baits
How do you control against summer mastitis?
- Synthetic pyrethroid ear tags/pour on products
- Graze open fields away from woods and streams
- Weekly tar/micropore tape application of teats
- Prevent teat lesions
- Dry cow tubes
