there is a paper that might be helpful for your purpose:
Bird, A. F.. A method of distinguishing between living and dead
nematodes by enzymatically induced flourescence. Journal of Nematology
, 103-105. 1979
The author states that the technique is quick (results in 15 min).
Anyway, it makes the use of fluorescein diacetate (FDA) and
fluorescence necessary and I never tried it by myself.