Otto followed up his 71 on Thursday with a nine-birdie effort that has him to 9-under and two strokes up at the halfway point. He is looking for his second win of the season, having won the Nashua Masters last November.
Dunlop sits alone in second place at 7-under for the tournament following a bogey-free day at Leopard Creek Golf Club near Kruger National Park. His tied fifth at last week 's Dimension Data Pro-Am in Sun City will serve him well as he heads into the weekend.
He is closely followed by Mark Mouland of Wales and first round co-leaders Richard Sterne and Titch Moore, both from South Africa. Mouland matched Otto for the course record with eight birdies and no bogeys.
Otto, currently fifth on the South African tour's Order of Merit, has played well here in each of the past two seasons. He finished sixth last year and posted a second place result in 2001.
I like the course. Its always a good test,' said Otto. 'They always want to knock us down on this course. Its important for me to do well here. But Im not feeling any extra pressure.'
Trevor Immelman is six shots off the pace as he carded a 2-under-par 70 and stands at 3-under for two days. The 23-year-old is laying claims to become the next great golfer out of South Africa, followong in the footsteps of Ernie Els and Retief Goosen.
His two victories in his last three outings, including the Dimension Data Pro-Am a week ago, has his confidence soaring, though in order to keep the hot streak alive he'll have to go low this weekend.