My horses were vaccinated on Friday for Strangles with an IM vaccine in the chest. This morning all of the horses that received the vaccine had hard swelling in the pectoral muscle where the vaccine was given. One had difficulty walking out to the pasture.
I called the vet who told me reactions were common, to give them bute and a hot compress on the site, and so on. My concern, that I relayed to her, was that they had received a bad batch of vaccine since every horse had a reaction. I have never had any horse have a reaction before. Have any of you had a similar experience? Any ideas about how long the recovery should take?
I switched to the NASAL strangles vaccine years ago. I am kind of amazed that there are vets that still use the IM as their is a risk of Purpura with it. Yes the swelling is normal, a little bute and hot compress will do the trick. No its not likely a 'bad batch', this kind of reaction is perfectly normal even for large numbers of horses.
Wow, the IM vaccine hasn't been used in my area in years--since the IN vaccine was developed--because it often caused a worse reaction than strangles itself. Why did your vet use the IM instead of the IN? Has he always done so?
As far as I know, there is a risk of developing purpura hemorrhagica with both the IN and IM vaccines. It's an immune complex reaction that causes severe vasculitis and can lead to death. It happens in horses that have a high titer already when they are vaccinated (either from previous vaccination or active infection).
The IM vaccine does tend to cause reactions like abscesses and swellings. The IN vaccine is a modified live vaccine and reversion to virulence has been reported, which basically means it "reactivates" to active, infective bacteria. So both carry some risk.