Chapter 15 ERU

Question 1

What is Equine Recurrent Uveitis (ERU)?

Answer 1

A condition characterized by multiple recurrent bouts of inflammation of the iris, ciliary body, and choroid, with periods of remission.

Question 2

What are other names for Equine Recurrent Uveitis?

Answer 2

Moon blindness, iridocyclitis, and periodic ophthalmia.

Question 3

What is the peak age for the initial uveitis episode in horses?

Answer 3

4-6 years old.

Question 4

Which horse breeds are predisposed to ERU?

Answer 4

Appaloosa, Warmblood, and American Quarter Horse.

Question 5

What are the three clinical syndromes of ERU?

Answer 5

Classic, insidious, and posterior ERU.

Question 6

What characterizes classic ERU?

Answer 6

Active inflammatory episodes in the eye, followed by periods of minimal, chronic ocular inflammation.

Question 7

What are typical clinical signs of active ERU?

Answer 7

Photophobia, blepharospasm, corneal edema, aqueous flare, hypopyon, miosis, vitreous haze, and chorioretinitis.

Question 8

What clinical signs are associated with chronic ERU?

Answer 8

Corneal edema, iris fibrosis, posterior synechia, corpora nigra degeneration, miosis, cataract formation, vitreous degeneration, and peripapillary retinal degeneration.

Question 9

What is insidious ERU?

Answer 9

A form of ERU where inflammation remains at a constant, low-grade level, leading to chronic clinical signs.

Question 10

Which breeds are most commonly affected by insidious ERU?

Answer 10

Appaloosa and draft breed horses.

Question 11

What characterizes posterior ERU?

Answer 11

Clinical signs existing entirely in the vitreous and retina, with little or no anterior signs of uveitis.

Question 12

Which breed is most commonly affected by posterior ERU?

Answer 12

Warmblood horses.

Question 13

What is primary uveitis?

Answer 13

Acute uveitis caused by various infectious and non-infectious agents.

Question 14

What systemic disease is commonly associated with ERU?

Answer 14

Leptospirosis.

Question 15

What role do leptospiral antigens LruA, LruB, and LruC play in ERU?

Answer 15

They cross-react with equine ocular proteins, contributing to the immunopathogenesis of ERU.

Question 16

What is the blood-ocular barrier?

Answer 16

A barrier that consists of the blood-aqueous barrier and the blood-retinal barrier, preventing large molecules and cells from entering the eye.

Question 17

What happens when the blood-ocular barrier is disrupted?

Answer 17

Blood products and cells enter the eye, leading to inflammation and immune responses.

Question 18

What type of inflammatory cells predominantly infiltrate ERU eyes?

Answer 18

CD4+ T cells.

Question 19

What cytokines do CD4+ T cells secrete in ERU?

Answer 19

Interleukin 2 (IL-2) and interferon-gamma (IFN-gamma).

Question 20

What role do Th17 cells play in ERU?

Answer 20

They produce IL-17 and IL-23, contributing to the pathogenesis of ERU.

Question 21

What is epitope spreading?

Answer 21

The diversification of epitope specificity from the initial immune response to other epitopes, contributing to disease progression.

Question 22

What diagnostic tests help identify primary uveitis causes?

Answer 22

Complete blood count, serum chemistry profiles, serologic tests for specific infectious organisms, and conjunctival biopsies.

Question 23

What indicates intraocular production of anti-leptospiral antibodies?

Answer 23

A positive C value (intraocular titer greater than serum titer) and detection of organism DNA via PCR.

Question 24

What are common clinical signs of acute anterior uveitis?

Answer 24

Photophobia, blepharospasm, corneal edema, aqueous flare, hypopyon, miosis, vitreous haze, and chorioretinitis.

Question 25

What are the main goals of ERU therapy?

Answer 25

Preserve vision and control ocular inflammation.

Question 26

What treatments are used for acute ERU episodes?

Answer 26

Systemic and local therapy, including antibiotics, corticosteroids, and anti-inflammatory drugs.

Question 27

What role does cyclosporine (CsA) play in ERU treatment?

Answer 27

It helps prevent recurrent episodes of uveitis by inhibiting T lymphocyte activation.

Question 28

What are the clinical outcomes of CsA-releasing devices in ERU?

Answer 28

Significantly fewer flares and improved long-term control of ERU.

Question 29

What is the prognosis for vision in horses with ERU?

Answer 29

Guarded, especially in horses with multiple or frequent episodes of uveitis.

Question 30

What percentage of horses with leptospiral-associated ERU have unilateral disease?

Answer 30

50%.

Question 31

What percentage of Appaloosas with ERU have bilateral disease?

Answer 31

Over 80%.

Question 32

What happens if ERU is unilateral and no bouts occur in the opposite eye for two years?

Answer 32

It is uncommon for uveitis to develop later in the contralateral eye.

Question 33

What is the long-term prognosis for horses with ERU?

Answer 33

Guarded, with a significant percentage losing vision in one or both eyes.

Question 34

What is the prevalence of vision-threatening ERU in horses?

Answer 34

At least 1-2% of the horses.

Question 35

What percentage of horses in Dr. Dwyer's study lost vision in one or both eyes?

Answer 35

56%.

Question 36

What percentage of horses with ERU became completely blind in Dr. Dwyer's study?

Answer 36

20%.

Question 37

What is the role of molecular mimicry in ERU pathogenesis?

Answer 37

It contributes to the immune response against ocular tissues due to similarity with infectious agents.

Question 38

What role does bystander activation play in ERU?

Answer 38

It leads to the activation of immune cells that cause tissue damage in the eye.

Question 39

What are the key clinical signs for diagnosing ERU?

Answer 39

Corneal edema, aqueous flare, posterior synechia, corpora nigra atrophy, cataract formation, vitreous degeneration, and retinal edema or degeneration.

Question 40

What distinguishes primary uveitis from ERU?

Answer 40

Primary uveitis is a single event, while ERU involves multiple, recurrent episodes of uveitis.

Question 41

What is the significance of detecting organism DNA in intraocular fluid?

Answer 41

It strongly suggests that the organism is playing a causative role in the uveitis.

Question 42

What are the suspected antigens associated with the immunopathogenesis of ERU?

Answer 42

Retinal S-antigen, interphotoreceptor retinoid-binding protein, cellular retinaldehyde-binding protein, malate dehydrogenase, neurofilament medium, and leptospiral antigens LruA, LruB, LruC.

Question 43

What are typical clinical signs of chronic ERU?

Answer 43

Corneal edema, iris fibrosis, posterior synechia, corpora nigra degeneration, miosis, cataract formation, vitreous degeneration, and peripapillary retinal degeneration.

Question 44

What is the role of immunohistochemistry in studying ERU?

Answer 44

It helps identify the types of inflammatory cells and cytokines involved in the disease.

Question 45

What are the benefits of CsA implants in ERU treatment?

Answer 45

They reduce the frequency of uveitis flares and help maintain vision in affected horses.

Question 46

What systemic diseases can cause primary uveitis in horses?

Answer 46

Leptospirosis, onchocerciasis, Streptococcus equi infection, brucellosis, toxoplasmosis, equine herpes virus, equine viral arteritis, parainfluenza type 3, generalized septicemia, endotoxemia, neoplasia, and tooth root abscess.