"My bronze medal in Moscow was the first medal for a Russian hurdler at world championships, and now I improved it. I'm just super proud of myself and my coach.
"It's been hard three days, every race was tough and the final was the toughest. It was a challenge for everybody. I'm happy that our hard work all these years was not wasted," added the Russian.
Merritt, also the London 2012 Olympic Games gold medalist, has a kidney condition which will have a transplant early next week.