"Sitalaa, Smallpox and donkeys

[Somdev Vasudeva]

Can someone kindly direct me to literary references in Skt. explaining the 
connection of the Goddess "Sitalaa with smallpox and her vehicle the 
donkey? I have been informed that this deity is still worshipped in 
parts of Rajasthan where an annual festival is held in her honour 
involving a stick-dance performed by men wearing enormous skirts. Do any 
accounts or studies of this ritual exist?

Thank you,

Somdev Vasudeva