Many years before the rule of Celestia and Luna. The world of My Little Pony was a wild west theme. The ponies lived in towns and developing colonies. The only fear they had was bandits and outlaws, until a deadly virus hits the country faster than a six pony bank robbery. The ponies are throw until a world constant fear, soon his outlaw uncle comes to visit the

The population of Burnton slowly dies of the fever

*Note*
Around this time there are only earth ponies so no pegasus and unicorn.
Also Celestia and Luna aren't dead, They are immortal but are not in the storyline. They still raise day and night but no pony knows it.