2021.Iss2.RuminantOphthalmology

Question 1

Defining & diagnosing infectious bovine keratoconjunctivitis

What is the causative organism?

Answer 1

moraxella bovis
**gram neg bacteria

Question 2

Defining & diagnosing infectious bovine keratoconjunctivitis

Ulcers with IBK healing

Answer 2

heal 1-3 weeks, can recover at any stage
-may heal without any intervention in 4 to 7 days

Question 3

Defining & diagnosing infectious bovine keratoconjunctivitis

IBK primarily affects only the eyes of cattle, however conjunctivitis is a significant but secondary in what viral pneumonias:

Answer 3

-blute tongue
-Rinderpest
-bovine viral diarrhea
-malignant catarrhal fever
-infectious bovine rhinotracheitis (BHV-1)

Question 4

Defining & diagnosing infectious bovine keratoconjunctivitis

Describe the development of IBK lesions

Answer 4

–serous ocular discharge–> blepharitis & conjunctivitis
–3 days later cloudiness n center of cornea develops
– diffuse cloudiness in eye with center of cornea yellowing & thin
–> cornea sometimes ulcerates +/- rupture

Question 5

Defining & diagnosing infectious bovine keratoconjunctivitis

What is required for M bovis to adhere to the corneal surface?

Answer 5

pili

Question 6

The role of environmental factors in the epidemiology of infectious bovine keratoconjunctivitis

what are environmental factors that contribute to the pathology of IBK?

Answer 6

-mechanical vector: musca autumnalis De Geer
-UV radiation
-mechanical irritation of corneal from plants/dust

Question 7

Component causes of infectious bovine keratoconjunctivitis- the role of moraxella sp in the epidemiology of infectious bovine keratoconjunctivitis

Which virulence factor of Moraxella bovis is toxic to the corneal epithelium ?

Answer 7

RTX toxin (hemolysin)

Question 8

Component causes of infectious bovine keratoconjunctivitis- the role of moraxella sp in the epidemiology of infectious bovine keratoconjunctivitis

Which virulence factor of Moraxella bovis required for the its adherence to corneal epithelium (spp without this are not pathogenic)?

Answer 8

type IV pili
**necessary virulence factor

Question 9

Component causes of infectious bovine keratoconjunctivitis- the role of moraxella sp in the epidemiology of infectious bovine keratoconjunctivitis

what are the two most significant homologous virulence factors between M bovoculi & M bovis?

Answer 9

1. complete RTX operon (cytotoxicin)
2. TIV pilin proteins (pili)

Question 10

Component causes of infectious bovine keratoconjunctivitis- the role of moraxella sp in the epidemiology of infectious bovine keratoconjunctivitis

Why is determining the etiology in individual outbreaks is challenging?

Answer 10

b/c moraxella spp have been isolated from cases of IBK & normal eyes
**difficult to establish causation

Question 11

Component causes of infectious bovine keratoconjunctivitis- the role of moraxella sp in the epidemiology of infectious bovine keratoconjunctivitis

For microbiological sample collection, what is recommended?

Answer 11

ocular conjunctival sac is aggressively swabbed to culture for pathogens
– use of flocked swabs in liquid transport media offers enhanced collection & release of bacteria into the media

Question 12

Component causes of infectious bovine keratoconjunctivitis- the role of moraxella sp in the epidemiology of infectious bovine keratoconjunctivitis

When can false-negative culture results occur?

Answer 12

if there is contamination or multiple pathogens

Question 13

Component causes of infectious bovine keratoconjunctivitis- the role of moraxella sp in the epidemiology of infectious bovine keratoconjunctivitis

What are the benefits of the MALDI-TOF assay?

Answer 13

quick, accurate & economical to ID moraxella spp from culture
– allow differentiation of M bovoculi isolates assoc with dz vs those presenting as normal flora

Question 14

The evidence base for prevention of infectious bovine keratoconjunctivitis through vaccination

What are the bovine corneal defenses to bacterial infections, including

Answer 14

-precorneal tear film
-lactoferrin
-local ab response (IgA)
-systemic ab response IgG1 (serum to tears)

Question 15

The evidence base for prevention of infectious bovine keratoconjunctivitis through vaccination

Is there any evidence that supports the use of vaccines to reduce IBR?

Answer 15

No

Question 16

Component causes of IBR- non-moraxella organisms in the epidemiology of IBR

What are differentiating C/S between Moraxella bovis ocular lesions & Malignant catarrhal fever?

Answer 16

MCF:
- corneal edema- fine line that spreads centripetally from limbus
-uveitis
-systemically sick: high fever, salivation, purulent nasal d/c, generalized LN enlargement

Question 17

Component causes of IBR- non-moraxella organisms in the epidemiology of IBR

What differs between Moraxella bovis ocular manifestations vs Listeria monocytogenes?

Answer 17

L monocytogenes: corneal has minimal changes & lesions usu unilateral

Question 18

Evidence base for treatment of infectious bovine keratoconjunctivitis

Which antibiotics that are registered for IBR in the N. America?

Answer 18

-oxytetracycline: 9 mg/lb bwt IM or SQ
-tulathromycin

Question 19

Evidence base for treatment of infectious bovine keratoconjunctivitis

Is povidone iodine spraying effective tx for IBK?

Answer 19

-corneal lesion severity assessed using clinical scoring system by measuring surface area of corneal ulcers

**mean corneal lesion areas of calves txed with povidone iodine & oxytet were significantly less than those in the controls, which suggests povidone iodine spraying is effective

Question 20

Component causes of IBR: the role of genetic factors in the epidemiology of IBR

What is the reported heritibility of IBK?

Answer 20

Low to moderate

Question 21

Component causes of IBR: the role of genetic factors in the epidemiology of IBR

Are there genes that are associated with resistance to IBK?

Answer 21

yes

chromosome: 1, 2, 12, 13, 20 & 21 associated with IBK resistance