Ruminant Ocular Disease Flashcards
What is pinkeye?
infectious and contagious ocular disease of cattle characterized by conjunctivitis and ulcerative keratitis
- results in major economic losses in the industry
What signalment is most commonly affected by pinkeye? How do signs progress?
3-4 m/o calves up to ~2 y/o
- starts with excessive epiphora and squinting due to pain
- progresses to a central area of corneal edema
- edema can spread across the entire cornea
First sign of pinkeye:
epiphora —> excessive wetness around the eye with tracts
Pinkeye:
more progressed infection with central corneal edema
What happens following corneal edema if pinkeye is not treated?
ulceration can develop, causing the development of mucopurulent d/c +/- rupture
- neovascularization occurs around 10-14 days, extending to the center of the cornea
How do older lesions associated with pinkeye appear? What may be seen after healing?
yellow and fibrinous —> result of necrosis and infiltration of the cornea by WBCs, neovascularization, and granulation tissue development
faint white scar on cornea
Pinkeye:
early infection —> beginning of edema, epiphora, no neovascularization
Pinkeye:
ulcer development + neovascularization from margins
Pinkeye:
neovascularization around periphery + plaque of granulation tissue
What is the most common cause of pinkeye in cattle? When is culture necessary for diagnosis?
Moraxella bovis +/- Branhamella ovis, Moraxella bovoculi, Mycoplasma bovoculi
if treatment is not effective or an autogenous vaccine is planned to be made —> usually only need to see clinical signs
What is the most common cause of pinkeye in sheep and goats? What is the primary sign associated?
Chlamydia
conjunctivitis
What 5 antibiotics have been effective in treating pinkeye? What is commonly added?
- OTC - good adhesion to the cornea
- PPG - daily administration makes it better for dairy cattle
- Ceftiofur (Excenel) - good for lactating cows
- Tilmicosin (Micotil)
- Florfenicol (Nuflor) - good for calves
(ultimately, most are effective if given in a timely manner)
Dexamethasone
- all can be given subconjunctival to allow residual coating of the cornea
What surgical option is available for treating pinkeye?
third eyelid flaps
What is prognosis of pinkeye like?
good to excellent
- treatment within 1-2 days = recovery within a week
- treatment within 2-5 days = recovery within 2-3 weeks
- severely affected eye = recovery within 1-2 months
- recovery of sight unlikely with corneal rupture
Pinkeye course of healing:
Pinkeye following recovery:
small scar
- no tearing = no infection = no treatment necessary
Pinkeye, corneal perforation and partial blindness:
staring to resolve at day 38
Severe pinkeye:
glaucoma
What can worsen pinkeye outbreaks?
vaccinating with live IBR
- viremia and inflammation allows virus to reach eyes
What are some predisposing factors associated with pinkeye?
- UV light
- dust
- seed heads
- face flies
How can pinkeye be transmitted?
- direct contact
- aerosols
- fomites - face fly vectors
- found in nasal secretions in carriers (can also be cultured from unaffected eyes!)
What genetic susceptibility is associated with pinkeye?
- cattle with unpigmented eyes
- Bos indicus are less susceptible (Beefmasters < Holstein)
What allows for infection of Moraxella bovis in the eyes?
pathogenic strains have pili that allow attachment to corneal surface receptors, leading to the dermonecrotic endotoxin release —> entrance into stroma and breakdown of it with proteases and hydrolases = corneal rupture!
When should control measures for pinkeye be put into place? What 5 measures are available?
BEFORE peak fly season (July in NY)
- bacterin vaccines - antibody to prevent bacterial attachment, give a year after an outbreak to keep immunity up (not entirely reliable due to multiple strains and mutated attachment antigens)
- fly tags, insecticides - alternate between OPs and permethrin to avoid resistance
- isolate clinical cases
- mow pastures to keep seed heads to a minimum
- chlortetracycline in feed (VFD)
What are some differentials for pinkeye? How is pinkeye unique?
- IBR
- Mycoplasma
- Branhamella
- malignant catarrhal fever
- FB
- eyeworm
- trauma
central corneal edema
What are the drugs of choice for treating small ruminant pinkeye?
a. Chlorotetracycline
b. Mycotil
c. Oxytetracycline
d. Penicillin
A, C —> effective against Chlamydia
What are the 3 most common signs of infectious bovine rhinotracheitis? How is infection prevented?
- upper respiratory signs
- severe conjunctivitis
- high fever
vaccination
What eyeworm affects ruminants? How is it treated?
Thelezia gulosa
Ivermectin
What foreign body commonly affects ruminants’ eyes?
- grass/weed awns
- seedheads
What is the most common congenital cause of blindness in calves?
BVD infection in the mother —-> no ocular tissue
What are dermoids? How are they treated?
rare congenital defect of the cornea, where normal, hairy skin grows on the surface of the eyeball or eyelid
Lidocaine block + debulk + cryotherapy —> not necessary if there is no epiphora or irritation
In what ruminants is entropion most common? How are they treated?
lambs
- create scar tissue with minor excisions to roll out the eyelid
- inject Tetracycline
- pinch lower eyelids with pliers
