lyme disease

our 11 yr old mare showed high positive with no sign of lameness or fever. I asked t the vet over because I had major weight loss in my mare and couldn't understand how she could be losing weight with amount of food I was giving her. My farrier suggested a lyme test , so the vet took the blood, the result came back high positive. She use to show on the QH circut with my daughter but now she is just a back yard horse with no job at all. I started noticing last winter she was losing some weight so Iput 2 blankets on her and fed her all the hay could eat and increased her grain. couple weeks latterI took her blankets off and she looked the same so this time Iadded fat in her grain still the same, then this spring I thought with the new growth of grass she would gain the weight back nope she stayed the same I started feeding her beet pulp, free hay, alfalfa pellets and her grain, now remember this horse is not being exercised so she is just hanging around eating. Also remember this horse has no sign of lameness or fever and she had a great appitite (don't think i spelt that right) goes to show you just because your horse isn't lame or acting sick don't mean there isn't something like lyme cause major weight loss and muscle loss. My other 2 horses are doing fine and I was feeding her double what I fed them.