Goats are born without H. contortus; however,
they become infested with the worm when they
start grazing. The L3, or infecting larvae, are eaten
by the goats during grazing. The L3 larvae then
burrow into the internal layer of the goat's
abomasums (true stomach) where they develop to
a L4, or pre–adult larvae. The L4 molts into L5, the
adult form.