Render - Is it Hoary Allysum?
On 7/25, he first appeared ill and was seen by our vet. He was lethargic, fever of 104, given IM penicillin for 5 days. We started feeding him more grain & took him out of the pasture for short periods while we could watch him as he ate better grass, as pasture was short. He ate like he was starving and seemed somewhat better. On 8/13, he was again seen by the vet.as the weight was just falling off him and we noticed the swelling in his lower legs. Blood wk and stool spec were checked, but only brought more questions, as white count was low, though he was still running a fever. I then went to the Internet and found the information about the hoary allysum. Bute, which is an anti inflammatory, was suggested and we started giving him that after checking with our vet. He was then removed from the pasture. By 8/16, the swelling was all the way up his legs including his groin. I called the vet and picked up an oral antibiotic. Today Fire-Eye was much more perky, temp was normal, swelling had decreased. We still need to determine what made him sick and eradicate it. That's where we need your help. I've given the resident (of Decatur County) the link to the following: http://www.extension.umn.edu/agriculture/horse/pasture/hoary-alyssum/
Warren County Iowa
Without seeing a picture of the plant you are suspecting, it is difficult to say for certain, although many of the symptoms sound similar. Hoary Alyssum is very, very difficult to eradicate, but keeping pastures from getting overgrazed, regular clipping before weeds go to seed, use of herbicides, and manually tearing up the plants may all be options. Starting over completely with respect to tearing up and reseeding the pasture is another.
Has your veterinarian also ruled out Potomac Horse Fever or a similar illness? The fact that antibiotics helped make me suspicious of that as well.