Why did the Mushishi anime air in a different order compared to the manga?


According to
[Wikipedia](http://en.wikipedia.org/wiki/List_of_Mushishi_episodes), the order
of the anime does not follow the same chronology as the manga. However, with
the series being episodic (and relatively self contained), and each episode
barely any passing reference to one another. Why did the production change up
the order in the anime? Was there ever an officially stated reason?

