Re: strangles

[CMNewell <reshan@deyr.ultranet.com>]

I'm a DVM. I make no claims to being "good", but I've dealt with a lot of 
strangles and done a reasonable amount of vaccinating , both IM and IN.

The disease itself, in the vast majority of cases is a big pain in the ass, 
messy to deal with, will blow a big chunk of your ride season, and 
generally be aggravating.
But it won't kill the horse, and the incidence of bastard strangles is 
quite low. Small comfort if the one horse out of  an entire outbreak that 
gets it is yours, I know, but no reason to panic.

I don't recommend vaccination if the risk of exposure is low. If the risk 
is high, the IN is probably better than the IM. The IM is made from a 
purified M protein portion of the bacterium, and cannot cause the disease. 
It can and often does cause a significant local reaction with lots of heat 
and swelling, and can occasionally set off a case of purpura hemorrhagica, 
an immune mediated vasculitis which is a very ugly complication (and can be 
a result of natural exposure to S.equi as well as several other things.)

The IN vaccine is a mutated form of live S.equi that is 
heat-sensitive--i.e., it (theoretically) will only grow in the relatively 
cooler nasal passages and not deeper in, as in the local lymph nodes.
Theoretically, this should be a much better vaccine, as it produces an 
immune response with secretory immunoglobulins rather than circulating 
ones, and  gets the bug before it can invade. Some horses have a day or 
three of slight elevations in temperature, and mild respiratory signs. From 
other posts here, it would seem that  there have been more severe reactions 
as well, though I have not seen any.

There have been several reports of horses developing abscesses in other 
spots after use of the IN vaccine. these were found to be injection sites 
for other vacines that were given after the IN, and the thought is that 
either an aerosol or contamination of the vet's fingers  resulted. the 
manufacturer of the IN now advises that, if injections are done at the same 
visit, that they be completed before the IN vaccine is used.

If your horse gets exposed to the bug, and you find out after removing it 
from the source of exposure, but before it develops symptoms, you may be 
able to stave off an infection by a short course of prophylactic 
antibiotics. (I have done this with a horse which had *just* started with a 
fever, but no abscesses yet.) I would leave this to your vet's discretion.



For those of you interested, there's a copy of a basic  FAQ I wrote  for a 
barn in the middle of an outbreak some years back, and it's posted  here:

ftp://ftp.ma.ultranet.com/pub0/r/reshan/STRANG.TXT

                         --CMNewell, DVM