Afrika and Du Preez both played incisive roles in Tokyo, where the South Africans won the tournament to move up to the second place in the World Series standings behind New Zealand.
Afrika (knee) and Du Preez (groin) were pulled out of the touring squad on medical advice, but could still be available for the final round of the Series in London.
The unavailability of the two players means 19-year-old WJ Strydom, who has been part of the national Sevens Elite Player Development squad, will make his debut.
Treu, however, welcomes back Paul Delport and was delighted to include Justin Geduld and Seabelo Senatla. Both youngsters just toured Argentina with the South African Under 20 training squad recently and could be named in their Junior World Championship squad on Thursday.
In a third change from the Tokyo winning squad, Pieter Engelbrecht replaces Tshotsho Mbovane.
“Injuries are part and parcel of any team, but we really had the worst of it in the last couple of months,” said Treu.
“The depth of our squad has been tested severely this year and I am proud of the way we responded when the team seemed down and out.
"The attitude of the guys is great, despite the injuries to our playmakers. Everyone realises that we will have to graft to achieve success this time around and everyone is looking forward to that challenge.”
South Africa will face Samoa, Canada and Kenya in Pool A of the Emirates Airlines Glasgow Sevens, to be played on 4-5 May at Scotstoun Stadium in Glasgow.SA Sevens squad: Frankie Horne (captain), Chris Dry, Philip Snyman, Jamba Ulengo, Cornal Hendricks, Pieter Engelbrecht, Stephan Dippenaar, Justin Geduld, Seabelo Senatla, Steven Hunt, Paul Delport, WJ Strydom
