His international debut came at the 2010 IAAF World Cross Country Championships, where he came 18th and helped Uganda to the junior bronze team medals. His junior career took off the following year as he was the junior silver medallist behind Geoffrey Kamworor at the 2011 IAAF World Cross Country Championships, then won bronze medals in the 5000 metres and 10,000 metres at the 2011 African Junior Athletics Championships. Ayeko stepped into the senior category in 2012 and began to focus on track running, running a 5000 m best of 13:23.25 minutes for second at the Memorial Primo Nebiolo and a 10,000 m best of 27:43.22 minutes in Birmingham.