There has been a bit of a kerfuffle around here about something called Herpes, or Rhinopneumonitis.  A horse in Georgia was diagnosed with it and a bunch of horses in New Mexico at a racetrack are under quarantine.  A few of the horses in New Mexico have even had to be euthanized.  That got the curiosity of this cat piqued.  Euthanasia seems pretty serious.

Herpes viruses are really good at hiding.  Like time for the cat to go the vet, can’t find them anywhere hiding.  This virus lays dormant in nerves until it feels the immune system is busy elsewhere.  Then it pounces, again let’s go with a cat metaphor, like a cat on a toy mouse filled with catnip.  Usually the horse experiences a snotty nose, maybe a cough, and sometimes a mild fever.  This goes on for a few days before the immune system gets back to work and brings things under control.

Vaccination is really important for immune system control of Rhinopneumonitis.  A well vaccinated immune system recognizes that the virus is out and about and attacks it faster.  This means less virus is put out in the environment.  It makes it a little complicated to understand, but essentially, by vaccinating a horse we don’t protect them, but we do protect every horse they come in contact with.  For this reason horse shows, racetracks, and many horse events have started asking for proof of vaccination for entry.

Ok, I asked, I’m sure the horses at the racetrack were vaccinated, so why did they get it? I’m a really smart cat so I pick up on these sorts of details.  It turns out Rhinopneumonitis has experienced a mutation which makes it harder for the immune system to see, makes it spread really quickly while the immune system is distracted, and causes havoc in the nervous system while it’s doing the first two things.  Horses with this particular kind of Rhinopneumonitis (also called EHV-1) can go years without showing any symptoms.  However, if a stressful event causes them to start shedding virus it passes like wildfire through a stable.  Infected horses can keep shedding virus for weeks! Quarantining affected stables ends up being the only way to stop the spread since vaccination can’t help once horses have been exposed. The good news on this version is that once it is identified and quarantine procedures put it place it is often stopped quickly.  Twice daily temperature-taking identifies affected horses quickly when treatment can still save them.

There’s another version of Rhinopneumonitis that very rarely causes a severe pneumonia that leads to scar tissue in the lungs.  This version, EHV-5, is usually responsible for what we lovingly refer to as the yearling snots.  As young horses get out and see more horses, experience some training, and are introduced to life, they often catch colds.  I’m told human children experience a similar phenomenon.  Most babies experience a few of these on their way to adulthood with only minor hiccups.  Sometimes though, the body wildly overreacts to the virus.  Another cat metaphor: Like a cat reacts to water-very badly.  In these horses the body attacks the lungs and turns them into scar tissue.  Unfortunately, I’m told the humans don’t have great treatment options for this form.

Turns out Rhinopneumonitis is just plain tricky.   Vaccination is good, but not a cure-all.  I’m told being cat-like is the best prevention.  Don’t take life too seriously and stay well rested.