The Japanese rider received the ban due to an anti-doping control positive for acetazolamide – a banned diuretic used to treat altitude sickness.
Acetazolamide is banned under the World Anti-Doping Agency code and is now the reason Oka will not return to action until May 24, having tested positive on December 13 of last year.
Oka’s absence spells further trouble for Delko, who, according to La Provence, are cutting their race programme and personnel due to budget shortfalls.
Delko’s sports director, Gorka Guerricagoitia, will leave the team on May 1, along with Jose Azevedo and four other members of staff.
The team last competed at the Tour of Turkey, an event won by rider Jose Manuel Diaz, but are once again in financial trouble after the UCI initiated bank guarantee proceedings last November.