Stallion sheath Swelling/Sores

Question
QUESTION: I have just had a stallion placed in my care (from my sister). He has always been prone to weepy eyes and usually gets a bit of an infection once a year (probably allergy related). A few days after his arrival he did get an infection in his tear ducts, which was was checked and treated by a vet with some steroid cream. A few days later, for what seamed no apparent reason, his sheath became hugely swollen. He also quickly developed quite a few open sores (Summer Sores??) which seem to be getting worse, even though we are getting the swelling of the sheath down with antibiotics. I am very concerned about the sores. They are at the opening of the sheath and on the tip of his penis and other areas of his penis. It is very hard to keep the flies off during the day. We are rinsing him twice a day, using medicated swat to try and keep flys off, but it actually seems to be getting worse (the sores). We are also giving him ivermectin daily to keep larve from growing in the open sores. Am I missing a more serious problem by thinking this is just summer sores brought on by the swollen sheath? Now, he is a stallion, and new to this barn. There is a mare across from him that was in heat a week ago, not sure if this could be a cause or not (over stimulation). At his previous location he was used to tease mares and occasionally live cover breeding, so he is used to reacting to mares in heat. Am I on the right track here with the antibiotics and swat and cleaning, or could this be something worse than I think, that needs immediate medical attention. The sores are open and red, weaping fluid and blood, with yellowish hard flesh-like substance in the wounds (this has shown up more recently). Please let me know if you have any advice.

ANSWER: Eva,
  When was the last time his sheath was cleaned and checked for stones?
Anne Stepien

---------- FOLLOW-UP ----------

QUESTION: According to the previous owner, about 3-4 months ago.

Answer
Eva,
  A couple of things. Many medications are not meant to be used on any open areas, and could be making the problem worse. Also with frequent washing, you could be destroying the horse's "normal flora" that will help prevent infection.
  It could be summer sores...it could also be squamous cell carcinoma, sarcoids or "coital exanthema", which is caused by the herpes virus. I'm also wondering if part of the problem is a chemical irritation from the medicine and the frequent washing.
  I know it's expensive, but you really need to have a vet come in. It probably wouldn't be a bad idea to do a punch biopsy of one of the lesions/sores. You can search for a veterinarian who has a special interest in reproduction at www.therio.org, and you can search for someone who is board certified in theriogenology at www.theriogenology.org.
  If I can be of further assistance, please let me know. I will keep my fingers crossed that this is a simple problem with a simple solution!
Anne Stepien