Well, Seeger got it from "Religious Folk Songs of the Negro, as Sung on the Plantations" by Thomas P. Fenner, 1909, so it would count as a spiritual.

Since I don't see it in the Mudcat, I'm going to post it here. I think perhaps you've heard part of the part she calls the refrain as the third verse.

RISE UP, SHEPHERD AND FOLLOW

There's a star in the East on Christmas morn,
Rise up, shepherd, and follow
It'll lead to the place where the Savior's born,
Rise up, shepherd, and follow

Refrain
Leave your sheep and leave your lambs
Rise up, shepherd, and follow
Leave your ewes and leave your rams
Rise up, shepherd, and follow
Follow, follow
Rise up, shepherd, and follow
Follow the star of Bethlehem
Rise up, shepherd, and follow

If you take good heed of the angel's words
Rise up, shepherd, and follow
You'll forget your flocks, you'll forget your herds
Rise up, shepherd, and follow
Refrain

From Seeger "American Folk Songs for Christmas" CD^^

This version also in Ruth Crawford Seeger's book, American Folk Songs for Christmas