Worms in eggs

Cracked an egg this morning and found that it had this worm in the white portion. First time we’ve seen this since getting chickens.

What is this type of worm and what’s the best treatment?

We have a flock of 18 and all seem okay. One of them is a bit slow but has been for a while. They have recently started properly free ranging after the winter. We cracked a few more eggs and didn’t see any worms in them, does this mean it could be that only one or so hens has the infection?