Polyarthritis is an infectious disease of nursing lambs, recently weaned lambs, and feedlot lambs. Symptoms are stiffness, reluctance to move, depression, loss of body weight, and conjunctivitis. Clinically the disease is primarily characterized by stiffness and by conjunctivitis. Body temperatures over 104°F are common. Lambs can be treated with several different broad-spectrum antibiotics or tetracycline drugs.