In fairness, the article isn't saying that the ritual is spreading the plague. It's saying that because the plague is currently hitting Madagascar, that this weird corpse dancing tradition could worsen the spread.
To some extent, I actually doubt that it will spread the plague, just because it seems like this is a thing they do years after they bury a corpse. By then, all the plague-causing bacteria in the corpse should be long dead.
In other words, this ritual seems gross and probably a health hazard, but it's likely not the reason why Madagascar is getting hit by the plague.