The etiology of "alveld" elucidated by the BSP-test.

The lamb disease called alveld is caused by Narthesium ossifragum. It is observed clinically in white lambs as a photosensitization, which may become very severe. At a more advanced stage, icterus often occurs as well, the latter affecting both black and white lambs. Adult sheep are rarely affected by alveld. Presence of phylloerythrin in the blood is a prerequisite for the photosensitization. Phylloerythrin is formed by microbial action from chlorophyll and is normally excreted in the faeces and the bile. Sufficient excretion fails in lambs getting alveld. The function of the liver has been examined in 40 lambs which had grazed for 10 days on Narthecium ossifragum, using the BSP-test of Rosenthal & White (1925). Fourteen out of 40 lambs showed a pathological liver dysfunction, while no clinical symptoms could be observed. Five to seven days thereafter 9 out of the 14 lambs with liver dysfunction became subject to photosensitization. (Table I). The ability of the BSP-test to indicate alveld at an early stage was statistically significant. It is concluded that liver dysfunction precedes photosensitization.