This is a line from Ørberg’s Roma Aeterna XL.170. I am not sure I understand prae se agit. It seems odd to imagine Aeneas driving Dido before him as a ploughman drives an ox. I believe I have found the original verse in the Aeneid: Agit ipse furentem in somnis ferus Aeneas. I suppose this could mean that he drives her crazy. What are your thoughts?
what in this line leads you to believe that there is a simile about a ploughman?
Isn’t it something like “and in a dream wild/fierce Aeneas himself drives her frenzied before him”
I vaguely remember something that I was told by a professor or came across myself from pretty early in my Latin studies associating ago with driving cattle.
I think it was comparing the Latin verb ago with the Greek verb of the same pronunciation, saying that the Latin more implied driving, whereas the Greek more implied leading.
Maybe Charlie Parker’s inspiration comes from Familia Romana, chapter 27 lines 13-14:
Arator duos validos boves qui aratrum trahunt prae se agit.
I thought of plowing myself when I read “prae se agit”, as I had recently read that chapter myself. 
Ago has many meanings. Whilst the first meaning is:
1 To drive (cattle, etc.). b praedam agere,
to drive off cattle, etc., as booty; ferre et agere,
to carry off (all movable and portable plunder,
cf. Gk. " Φερειν και αγειν). (no accents as I had to type the greek)
later on we have
5 (of men, circumstances, etc.) To force to
move on, drive. b (fig., of madness, etc.).
uesper ubi aut hibemus agit de montibus imber (se. aues)
'{ERG.G.4.474; ad ueterem portam Palati.. turba fugien-
hum actus LIV.I.IZ.3; et nondum fatis Dircaeus agentibus
exsul STAT.Theb.6.913; agebatur hue illuc Galba uario
turbae fluctuantis impulsu TAC.Hist.I.40j-(w. ante, prae)
paUida Tisiphone Morbos agit ante Metumque VERG.G.
3.552; qualis ubi. . uentos dux prae se Neptunus agit STAT.
Theb.3.433; senatum et populum ante se agens TAC.Hist.
2.8g;-(fig.) te tuus ardor aget PROP.I.13.28. b con-
scientiae stimu1is actum V,MAx.9.U.3; quaeque succensas
agit libido mentes SEN.Phaed.541; in potando necessarius
modus, ne lymphatos agat PLlN.Nat.31.9; STAT.Silv+4.86.
and many more pages…
So driving cattle is only one meaning
Perhaps better than “drives her frenzied” simply “drives her mad”?
I think the English idiom “drives her mad”, with 'mad" predicative, is not quite right here. She’s already furens. He’s driving her forward like cattle in her state of furor, as has been suggested. It’s a disturbing and raw image.
I take your point but I hadn’t actually intended “drive her mad” to be taken in that way. I had intended something like drives her mad as she was or something like that.
I can see where what I posted might have the implication that it referred mainly to driving cattle. I am well aware of the multitude of meanings. I would show my students the entry for ago in the Lewis Latin Dictionary for Students, which occupies almost 2 pages, and joke with them that if they were unsure what verb to use when going from English to Latin to just try ago, because it had a good chance of working.
I used driving cattle because that was how the professor explained it; if I recall correctly, that actually came up in a beginning Greek class. We were using Athenaze and working through a passage in which Dikaeopolis and the slave, whose name escapes me now, were heading to the fields with the plow-ox. I should have said when it was used to refer to compelling forward motion, such as with cattle, whether from behind or from in front.
I didn’t think that you thought of it in the way and I know you have better command of Latin than me. My post was really for Charlie who tends from past experience to go with meanings provided by Lingua Latina, which is always a good place to start but can cause problems.
Ørberg’s “prae se agit” may bring to mind driving like cattle but Virgil’s “Agit ipse furentem in somnis ferus Aeneas” is a more complicated affair. Ferus can mean fierce or cruel but it also means wild and perhaps conjures up the image of a wild beast. So perhaps there is some inversion of a hunt going on here, picked up later in the simile of Pentheus. Or maybe I am making too much of this. 
Thank you, my friends, for your insights. I should have included a reference to the earlier passage which Antonius Calvus kindly supplied. I find Hylander’s interpretation most helpful.