Clam farming, an increasingly popular business in coastal Virginia, is facing a threat with similarities to a parasite that devastated the state’s oyster industry.

A mysterious disease known as QPX has spread to 10 seaside farms stretching the length of Virginia’s Eastern Shore, with the potential to kill 90 percent of the hard clams it infects, scientists said.

“We take this very, very seriously,” said Bill Pruitt, executive director of the Virginia Marine Resources Commission, which regulates seafood and coastal ecosystems. “We do not want an environmental tragedy here.”

The commission voted unanimously to ban the importation of baby clams, or seed, from South Carolina and Florida for at least the next 180 days. Such seed is commonly planted on private beds on the bottom of Virginia’s many inland bays along the Atlantic Ocean.

A recent study by the Virginia Institute of Marine Science found that a high percentage of local QPX cases stem from clams originating from southern states. Seed reared in Virginia, New Jersey and Massachusetts, on the other hand, were less likely to develop the disease, according to the study.

The commission will allow imports from Northern waters. But it also barred clams from Pacific states, fearing an accidental introduction of QPX or some other predator. The panel agreed to lift temporary restrictions on seed brought to Virginia from a sophisticated hatchery in Hawaii, where inspectors turned up no problems.

As part of its deliberations, the commission also agreed to establish a task force to look into certifying state hatcheries and other means to better regulate the budding business of growing clams, estimated to be worth about $35 million a year.

QPX does not harm people, and the tiny parasite responsible for causing the disease has not been detected in the Bay or in wild clam populations anywhere in Virginia.

Still, news that the single-celled creature has spread throughout seaside farms just six years after being detected reminds scientists and seafood merchants of another parasite, MSX, that nearly wiped out state oyster stocks.

“Let’s not let history repeat itself,” said Tom Gallivan, a clam grower from Willis Wharf. He urged clam farmers to use only locally raised seed, which he and a handful of other entrepreneurs produce.

Other farmers complained that the ban would wreak economic havoc.

Hank Jones, a Cape Charles grower, said he has contracts for 6 million clams from a South Carolina distributor, but he now will likely lose his down payment and not have any seed to plant this fall. “At least let us follow through with our contracts,” he asked the commission. “Without them, I’m dead.”