Ekholm claimed her third world title with a flawless round ahead of two outsiders - Germany's Tina Bachmann at 2min 15.8sec and Ukrainian Vita Semerenko third at 2:52.1sec.
"Today I knew that the shoot would be decisive. It was an incredible relief when the the last target fell," the 26-year-old said after her win.
Conditions were tough for the biathlon athletes; as a storm raging in the Russian town it was unclear in the morning if the event could be staged.
Despite expressing a longing for the end of winter and the dawn of spring as she waited for event, Ekholm was assured as she alone claimed the full pot of 20 shots in the tournament.
The Swede has now hit 50 consecutive targets in this world championships.
German star Magdalena Neuner struggled home fifth with five penalties for missed targets with Finland's Kaisa Makarainen, the newly-crowned world pursuit champion and World Cup leader, finishing 28th with seven penalties.
The remaining Swedish competitors were left far back in the field, with Ekholm's younger sister Jenny Jonsson trailing in 36th, Anna Maria Nilsson in 39th and Anna Carin Zidek in 45th.