I am going to attempt to answer some
questions and give what should be a minimum horse owner's knowledge of the
disease. Unfortunately, our farm is in a micro-geographic region, the
Genesee River drainage basin, that has a high incidence of anterior
uveitis.
First, what is it? Well, the
underlying disease process is an inflammation inside the eye. "-itis" is
medical lingo for inflammation. Inflammation inside the eye is distinct
and different from that of the cornea and conjunctiva.
" Uvea: Part of
the eye, consisting collectively of the iris, the choroid of the eye, and the
ciliary body:
The iris: The circular, colored curtain of the eye that surrounds
the pupil.
The choroid of the eye: The thin vascular middle layer of the eye
that is situated between the sclera (the white of the eye) and the retina (the
nerve layer that lines the back of the eye, senses light, and creates impulses
that travel through the optic nerve to the brain).
The ciliary body: A body of tissue that connects the iris with the
choroid and includes a group of muscles which act on the lens of the eye to
change its shape.
The word "uvea" comes from the Latin word "uva" for grape. Why a grape? Well,
the idea was that, if the stem is removed from a grape, the hole looks like the
pupil and the grape the eyeball." (MedicineNet.com)
When inflammation occurs you have redness and pain. Following
that you have scarring. Scarring inside the eye is permanent damage.
This particular inflammation is thought to be caused be an allergic reaction to
the proteins inside the lens. This protein is antigenically related to
proteins in the Leptospira bacterium. As we all know tendencies to
allergy are family related. We have had Appy mother and daughter with
the disease, even tho the daughter did not inherit color; she was solid
bay.
As we all know,
the bouts of inflammation can recur, in the old days thought to be in concert
with moon cycles. With each succeeding bout, interior damage to the eye is
increased. One or a few attacks of uveitis does not make a blind horse,
but corneal changes (blueness), cataracts and adhesions of the iris to the
lens are seen after multiple attacks.
An attack is
very treatable, especially if treatment is started early. THUS
EVERY RED, SWOLLEN OR PAINFUL EYE IS A MEDICAL EMERGENCY!!!!!!! Your vet
should be able to distinguish inflammation inside the eye from pink eye or a
scratch.
Touch wood, we have not had an attack in our herd of 40+ horses
since we started vaccinating with the cow Lepto vaccine. How
the vaccine works, I do not know, but whether to vaccinate is very much a
geographical question! Adverse reactions to the vaccine that have been
reported that include elephant legs and sudden blindness. (Hence I use 1/2
cow dose per horse.) Cornell has done a lot of research, so is a place to
start for more information.
One year we did titers on our whole herd. The results were
not very useful in our approach to treatment, altho disease was related to the
presence of higher titers.
