Atlantic Canada has recorded its first outbreak of a microscopic parasite that threatens the future of the region's multimillion dollar oyster fishing industry.

A disease called MSX has infected oyster stocks in Cape Breton's Bras d'Or Lakes. The parasite doesn't affect other shellfish and is harmless to humans.

But MSX wiped out oyster stocks in Chesapeake Bay between Maryland and Delaware in the 1950s. Until now, it had never been spotted north of Maine.

Fisheries and Oceans scientist Sharon McGladdery said MSX could have a devastating impact. The highly contagious disease can be passed directly from oyster to oyster or float with the tide.

Since Cape Breton oysters are regularly transferred to waters around Atlantic Canada, the disease threatens the livelihood of more than 1,700 people in the region.

The DFO has issued a ban on oyster movement on Cape Breton's east coast to help contain the disease while McGladdery tracks how far it has spread.