WASHINGTON—Eighteen senators were sent home from Congress Tuesday after a routine screening found an infestation of nits, larvae, and adult parasites living on the scalps of high-ranking Washington lawmakers.

The outbreak of head lice, which many are calling the worst in U.S. Senate history, has brought the Capitol to a standstill, with presiding officer Vice President Joe Biden suspending all daily sessions until further notice.

"I regret to inform the American people that the Senate chamber has been struck by a devastating case of lice," majority leader Harry Reid (D-NV) said. "Although we've already dismissed a number of afflicted senators, and thrown out most of their personal belongings, it is imperative that this issue be resolved as quickly as possible."

Pediculus humanus capitis.

"This outbreak needs to be addressed," continued Reid, speaking from behind a podium wrapped in airtight plastic sheets. "We can't risk having lice spread to the House."

According to sources on Capitol Hill, signs of a potential infestation first surfaced early Monday morning when Sen. Thad Cochran (R-MS) witnessed Sen. Jay Rockefeller (D-WV) excessively scratching at the back of his head. Cochran, who sits directly behind Rockefeller, said that the five-term senator's aggressive attempts to relieve an itch dislodged several tiny, writhing bugs, which fell onto a binder containing bill S. 2294.

"It was so disgusting," said Cochran, adding that he thought Sen. Rockefeller only had dandruff. "I'll never cosponsor a bill with him again. I bet he doesn't even shower."

While Senate leaders would not release the name of the blood-feeding parasite's original host, many legislators speculated Tuesday that the epidemic started with that one gross Arkansas representative who always wears sweatpants.

Using a tongue depressor and a flashlight, Senate nurse Debra Barger personally examined each of the elected officials' scalps, and issued a stern warning to all present to avoid sharing hairbrushes, hats, and towels with other members of the governing body.

"I told the senators that they didn't need to feel humiliated," said Barger, who made Sen. John Kerry (D-MA) wear mittens to thwart his attempts to scratch his scalp. "And contrary to what Sen. Specter says, lice are not the most deadly form of cooties."

But despite Barger's best efforts to reassure the afflicted senators, many still felt stigmatized.

"Everyone is going to make fun of me now," said Sen. Dianne Feinstein (D-CA), who attempted to get rid of the lice by shaving her head. "This is so much worse than the time I puked on the Capitol steps."

Despite several days of lengthy debates, the remaining senators were not able to agree on a measure to remove the louse colonies. While one faction argued that the application of petroleum jelly or mayonnaise would suffocate the lice, Sen. Jim Bunning (R-KY) made a privileged motion that all affected heads be immediately soaked in kerosene.

By late Tuesday afternoon, a majority of senators had been sent back to their home states along with letters urging that family members and constituents have their hair checked for lice. With the legislative chamber nearly deserted, officials from the Department of Health and Human Services arrived on Wednesday to vacuum the Senate floor, spray down chairs and desks, and machine-wash all flags in hot water.

Since news of the infestation first broke, Congress has been inundated with angry calls from Senate parents, many of whom are blaming party leaders for the outbreak.

"We paid a lot of good money to get our children into the Senate," said Roberta McCain, 96. "Unless things change, I'll be transferring John to a better branch of government next year."

According to Beltway insiders, this is the worst contagion to hit the federal government since 2004, when a single infected gavel gave the entire Supreme Court crabs.