Emma Whitaker is part of an eight-strong team and will be making her second appearance at the event having competed on home soil 12 months ago.
The 16-year-old, who enjoyed victory at the Portuguese Under 17 National Championships in April, will be joined in the girls’ team by Warwick’s Georgina Mitchell, Hertfordshire’s Kamie Lowe and Plymouth’s Annabel Denton.
There is also a four-man boys’ team competing.
Wilton and Case, who finished 18th and 21st respectively at the 2016 Under 17 European Championships will be joined by Yorkshire Pentathlon Club duo Toby Price and Josh Hood.
The championships in Pazardzhik will follow the modern triathlon format which sees all athletes complete a 200m swim before the laser run, combined running and shooting.
The individual competitions take place on Friday, June 30, with the mixed relays following on Sunday, July 2.
City of Lancaster Triathlon Club’s Whitaker will be hoping to build on her performance at the Under 19 European Cup in Barcelona, where she competed in a higher age class.
She finished 21st in the individual event on Saturday before teaming up with Hood to come 13th in the mixed relay against a strong international field in Sant Boi.