Congenital tracheal stenosis in lambs induced by maternal ingestion of Veratrum californicum.

Seven of nine lambs born to six ewes gavaged with Veratum californicum root and rhizome material on days 31, 32 and 33 of gestation died from asphyxia within 5 minutes after birth. Five of the seven were autopsied and found to have severe stenosis of the trachea. None of the 12 lambs born to seven control ewes had tracheal stenosis. The defect was characterized by lateral flattening of the trachea throughout its entire length. Cartilaginous tracheal rings were reduced in number, nonuniform in size and shape, irregularly spaced, and with abnormal orientation. The rings were thinner than those of control tracheas, and had zones of chondrogenesis on outer and inner surfaces which were of equal width, rather than of unequal width as in controls. The smaller size and relatively noncurved shape of the cartilaginous rings of the stenotic trachea resulted in a nondistended lumen.