This summer, I managed a horse training and boarding facility in southeastern Kansas. One morning, I was turning out horses, and noticed that one of the mares had strange marks on the sides of her jowls and neck, and also near her forehead. They looked almost as though the skin had been rubbed off of them. (Similar to a "rug burn") I asked the barn owner about the marks, and he said he had never seen anything like them, but assumed it was some sort of allergic reaction, since the mare's fly mask had been washed recently. I kept the mare inside, with the intention of keeping an eye on her during the day.
While I was cleaning stalls, I began hearing kicking and sounds of distress coming from the mare's stall. I monitored her for about three minutes, and noticed that she had become frantic, pacing in her stall, kicking the boards, and breathing heavily. She did not, however, roll, look at her stomach, or show any typical signs I would associate with a colic case. After a few minutes, the mare went into a sort of "trance". She stood facing the back of her box stall with her head hung.
The farm owner had left the farm at this point, and I was alone for the day. With nobody else to consult regarding the issue, I called the veterinarian who the mare's owner used. I explained the signs that the mare was showing, including the marks on her head/neck, the period of excitability, and the "trance"-like state. I explained that I had never seen anything like it, and thought it might be an emergency. The receptionist that I was speaking to then put me on hold, saying that she'd ask the veterinarian what to do. She put me on hold for five minutes.
In that five minutes, the mare walked over to the corner of her stall and placed her head against a board. She then began head pressing, and I noticed that this must have accounted for the hairless patches on her head and neck. (I confirmed this later, when I found patches of hair stuck in the boards of the stall.) Then, it appeared that she became incredibly weak, and attempted to support herself against her automatic waterer. Her legs then appeared unable to support her, and she fell to the floor. She appeared to go into convulsions, with her legs becoming stiff, her muscles twitching, eyes rolling back, and tongue lolling out of her mouth. After about one minute, the seizing appeared to slow, and I entered the mare's stall. Her breathing became very shallow. I checked her gums, and they appeared extremely pale. Her eyes were bloodshot to the extent that the sclera was completely red. The receptionist picked up the phone at this point, and told me that a veterinarian would be there shortly. I told her that it was probably too late.
The mare's breathing became sporadic. I tried to get her up, or even to keep her "awake", to no avail. Her breathing slowed to a stop a few minutes before the veterinarian arrived.
The veterinarian entered the stall, asking me, "Is she alive?". I told her that her breathing had stopped a few minutes ago, as she checked the mare's clinical signs. She informed me that the horse was dead, as if I hadn't known this. She checked the mare's gut, and said simply, "The mare colicked.". I was appalled. However, I didn't want to argue with the just-graduated "professional", and thanked her for hurrying out to the farm.
After the incident, I went home and contacted other veterinarians, researched information in books and on the internet, and spoke to other professionals in the horse industry. I believe that this mare may have suffered hepatic encephalopathy, or something very similar. Afterwards, I went out and checked all of the pastures on the farm. I identified Nightshade, as well as several other toxic plants, along the fencelines of several paddocks. (I had this brought to the owner's attention, and they removed them promptly.) I also suspected a possible aneurysm, or stroke, judging by the signs.
She was an 8 or 9 year old Dutch Warmblood mare. She had never had any medical conditions, to my knowledge. She was rarely exercised. She was ridden once every two weeks. She spent half of her days on pasture, and half in a box stall.
No other horses on the farm became ill or produced similar signs.
This mystery has kept me guessing for months now. I have consulted several other equine veterinarians, all of whom have their own opinions as to what may have happened to the mare. I would very much appreciate any input that others may have. This was a truly traumatizing experience for me, as a pre-veterinary student, and has highly influenced my desire to become an equine veterinarian.
Thank you in advance for your help. It's much appreciated!