Recently treated for benign vertigo with physical therapy. Can I safely ride on a plane for very long flight to africa?

Yes. Depending on how long ago you had the manipulation you may need to keep your head fairly still for a day or two. Otherwise you can fly without fear.
Vertigo. Benign positional vertigo is simply the positioning of a very small bone like object in the canal of a tube lined with sensitive nerve fibers. These fibers sense where that bone is as it floats along with your head. When it gets "stuck", the mix-up in the signal of where that bone is verus where it should be causes the spinning of vertigo. The flight should not make it restick.