Greg Page, the lead singer of internationally successful childrens group The Wiggles [ tickets ], is stepping down after 15 years because of a chronic health condition.

Understudy Sam Moran has replaced Page as the Yellow Wiggle and the group will continue to tour, according to a statement on its website. The Wiggles kick off their annual year-end outing in their home of Australia tonight (Nov. 30) in Perth. Dates are listed at their website.

Page suffers from a condition called orthostatic intolerance, which causes problems with walking, balance, speech and coordination but is not life threatening. Specialists believe his illness, thought to be genetic, dates back some 12 years but has become more severe.

Page said that his decision to leave to the group he co-founded 15 years ago was very difficult.

"I will miss The Wiggles and the other guys very much, as well as seeing all the children in the audiences that we perform in front of," he said in a statement. "I wish the guys continued success, and welcome Sam Moran with open arms to the Yellow Skivvy--I know he is a great performer, and is well equipped to be the Yellow Wiggle.”

Moran has been with The Wiggles for the past nine years and has performed more than 150 shows as the Yellow Wiggle understudy.

Page withdrew from the group's US tour in June after suffering from fainting spells and lethargy, according to BBC News. The Wiggles just finished a North American tour in November.

Last year, The Wiggles were Australia's highest-earning entertainers for the second year in a row, according the country's Herald Sun newspaper. They won their fifth ARIA Award this year for best Australian children's release, and were named Australian Exporter of the Year.

The Wiggles' September album release, "Racing to the Rainbow," is the latest work added to their huge catalog of music, television, video and film projects. The group has sold more than 17 million DVDs and 4 million CDs worldwide, according to their bio.