I have an ewe that was just not fairing well all winter,not much interest in food, no weight gain, still born lamb, and was starting to lose weight.  as soon as the weather allow I pull her out, haltered her and gave her a bath. while bathing her I discovered an abcess under her belly.  I had the vet come and pull blood to be sure that that was all I was dealing with. It took a long time to heal the abcess but she is finally starting to gain some weight.  Perhaps she laid on something that puntured her but it wasn't enough to bring her down she just became untrifty. So make sure you put your hands all over that ewe.