Endurance.Net Ridecamp Archives

On Sat, 2 Jun 2007 20:57:38 +0300, Maryanne Gabbani wrote
> Rats and mice are an even more common reservoir for lepto. It used to be
> known as Rat Catcher's Disease. In humans doxycyline is the antiobiotic for
> you. I keep Rat Terriers for it. Human doctors aren't altogether up to date
> on it as well.
Doxycycline is the antiobiotic my vet prescribed for my mares.
In the World Health Organization paper, I think they were using
it prophylactically on people living in known contaminated areas.

Unfortunately, doxycycline isn't supposed to be consumed by
pregnant mares.  So, if I'm going to use it to make sure that
I start her pregnancy with as clean a bill of health as possible,
I've got to "purge" her long before she's bred.  I can't treat her
during pregnancy.

Vets used to think that the Moon Blindness reocurred even after
the lepto was purged from the system, like some kind of hypersensitivity
reaction to dust.  Thus, they tended to not use gloves when
treating the eyes and took no precautions against contamination
when switching from poking and prodding the inflamed eye to poking
and prodding the other, often healthy eye, or when moving from a
sick horse to healthy horse in a herd.  Heck, lepto as the cause
of "recurrent uveitis" aka "Moon Blindness" in horses wasn't even
recognized until the mid 1990's!

More recently, it has been established that the leptospirosis
bacteria *can* persist in the conjunctiva and tear ducts even after the
body has been cleared with antibiotics or the horse's own
immune system.  (Something about the eyes having the same kind
of "body-eye barrier" like the "brain-blood" barrier.)  So, vets
(and owners) have to work to prevent casually spreading the infection
from one eye to the next, or from one horse to the next.  Or
from the horse to themselves.

Another important thing about lepto is how differently it affects
different species.  It's favorite hangout is the kidneys/urinary
tract.  But in horses it also likes the reproductive tract.
The WHO paper says that, in humans and dogs it frequently quietly
infects the kidneys and slowly destroys them over the course of years,
often without any overt symptoms at all until it's way too late.

It also seems to be difficult to establish firmly that the horse is
free of infection.  Lepto titres are very tricky tests, very inclined
to yield false negatives and false positives.  Lepto has many, many
sub-types (serovars).  The sub-types mutate rapidly.  A titre calibrated
in one year can easily become meaningless the next year when a new variety
invades an area.  For example, one paper I read said the dominant form of
lepto around East Tennessee used to be Leptospirosis Hardjo.  Now, that
has been overwhelmed by something called Leptospirosis Pamona.  (I wonder
if it had anything to do with the coyotes moving into the area.)

If anybody is interested in this topic, I've got lots of great links
and articles I've already downloaded.  The emphasis is on the
more densely technical articles (vet journals and the like).

Linda Mirams










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