Summer Sores

Dear Dr. Lowder, I have a 9 year old Saddlebred gelding that had his sheath swell up after his fall vaccines and a sheath cleaning. It swelled so bad that the skin on the prepuce area cracked and bled.

Story originally posted by: Michael Lowder, DVM, MS

At first I thought that it may have been caused by the povidone scrub used to clean his sheath. My vet said he got summer sores and to worm him and give him Azium. We live in the desert so flies are a year round reality. The sheath took months to get somewhat back to normal, but never 100%. Then in April when he got his spring vaccines the next day it was swollen like a bowling ball again.

I have been worming him every 2 weeks, and keeping flies away the best we can in the summer. He had a bad episode this week, it was raw and even had discharge on it. I started him on SMZ tablets, and wormed him again, after 3 days it looks a little better, but still raw. My vet came out and says that he will always have this problem.

I read that ivermectin can be used topically, have you heard of this, and is it safe? I feel we have nothing to lose at this point. Also does the swelling sound like it is more of a reaction to vaccines than anything else? The common denominator vaccine would have been flu/rhino.

Priscilla Dewing


First, if the flu/rhino is the problem stop giving them. Second, it sounds like this pony needs to be on a antibiotic and steroids. Ivermectin topically will not help this.

If the pony does have “summer sores” or “genital bursatti” which are granulomatous growths that are friable and bleed when manipulated pruritus may be intense.

To get a diagnosis have your vet take a skin biopsy and send it to a lab. Treatment includes local application of insecticides, ivermertic administration and surgical removal of the granulomas.

Thank You,
Dr. Lowder