Ruminant Ocular Disease

Question 1

What is pinkeye?

Answer 1

infectious and contagious ocular disease of cattle characterized by conjunctivitis and ulcerative keratitis

• results in major economic losses in the industry

Question 2

What signalment is most commonly affected by pinkeye? How do signs progress?

Answer 2

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

Question 3

First sign of pinkeye:

Answer 3

epiphora —> excessive wetness around the eye with tracts

Question 4

Pinkeye:

Answer 4

more progressed infection with central corneal edema

Question 5

What happens following corneal edema if pinkeye is not treated?

Answer 5

ulceration can develop, causing the development of mucopurulent d/c +/- rupture

• neovascularization occurs around 10-14 days, extending to the center of the cornea

Question 6

How do older lesions associated with pinkeye appear? What may be seen after healing?

Answer 6

yellow and fibrinous —> result of necrosis and infiltration of the cornea by WBCs, neovascularization, and granulation tissue development

faint white scar on cornea

Question 7

Pinkeye:

Answer 7

early infection —> beginning of edema, epiphora, no neovascularization

Question 8

Pinkeye:

Answer 8

ulcer development + neovascularization from margins

Question 9

Pinkeye:

Answer 9

neovascularization around periphery + plaque of granulation tissue

Question 10

What is the most common cause of pinkeye in cattle? When is culture necessary for diagnosis?

Answer 10

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

Question 11

What is the most common cause of pinkeye in sheep and goats? What is the primary sign associated?

Answer 11

Chlamydia

conjunctivitis

Question 12

What 5 antibiotics have been effective in treating pinkeye? What is commonly added?

Answer 12

1. OTC - good adhesion to the cornea
2. PPG - daily administration makes it better for dairy cattle
3. Ceftiofur (Excenel) - good for lactating cows
4. Tilmicosin (Micotil)
5. 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

Question 13

What surgical option is available for treating pinkeye?

Answer 13

third eyelid flaps

Question 14

What is prognosis of pinkeye like?

Answer 14

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

Question 15

Pinkeye course of healing:

Answer 15

Question 16

Pinkeye following recovery:

Answer 16

small scar

• no tearing = no infection = no treatment necessary

Question 17

Pinkeye, corneal perforation and partial blindness:

Answer 17

staring to resolve at day 38

Question 18

Severe pinkeye:

Answer 18

glaucoma

Question 19

What can worsen pinkeye outbreaks?

Answer 19

vaccinating with live IBR

• viremia and inflammation allows virus to reach eyes

Question 20

What are some predisposing factors associated with pinkeye?

Answer 20

• UV light
• dust
• seed heads
• face flies

Question 21

How can pinkeye be transmitted?

Answer 21

• direct contact
• aerosols
• fomites - face fly vectors
• found in nasal secretions in carriers (can also be cultured from unaffected eyes!)

Question 22

What genetic susceptibility is associated with pinkeye?

Answer 22

• cattle with unpigmented eyes
• Bos indicus are less susceptible (Beefmasters < Holstein)

Question 23

What allows for infection of Moraxella bovis in the eyes?

Answer 23

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!

Question 24

When should control measures for pinkeye be put into place? What 5 measures are available?

Answer 24

BEFORE peak fly season (July in NY)

1. 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)
2. fly tags, insecticides - alternate between OPs and permethrin to avoid resistance
3. isolate clinical cases
4. mow pastures to keep seed heads to a minimum
5. chlortetracycline in feed (VFD)

Question 25

What are some differentials for pinkeye? How is pinkeye unique?

Answer 25

• IBR
• Mycoplasma
• Branhamella
• malignant catarrhal fever
• FB
• eyeworm
• trauma

central corneal edema

Question 26

What are the drugs of choice for treating small ruminant pinkeye?

a. Chlorotetracycline
b. Mycotil
c. Oxytetracycline
d. Penicillin

Answer 26

A, C —> effective against Chlamydia

Question 27

What are the 3 most common signs of infectious bovine rhinotracheitis? How is infection prevented?

Answer 27

1. upper respiratory signs
2. severe conjunctivitis
3. high fever

vaccination

Question 28

What eyeworm affects ruminants? How is it treated?

Answer 28

Thelezia gulosa

Ivermectin

Question 29

What foreign body commonly affects ruminants’ eyes?

Answer 29

• grass/weed awns
• seedheads

Question 30

What is the most common congenital cause of blindness in calves?

Answer 30

BVD infection in the mother —-> no ocular tissue

Question 31

What are dermoids? How are they treated?

Answer 31

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

Question 32

In what ruminants is entropion most common? How are they treated?

Answer 32

lambs

• create scar tissue with minor excisions to roll out the eyelid
• inject Tetracycline
• pinch lower eyelids with pliers