The word rickettsias is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 18
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (57 words)
actress, airiest, airsick, artiest, artists, ascites, attires, cakiest, caskets, casters, cattier, citrate, cristae, iratest, irisate, kaisers, karites, karstic, kitties, raciest, racists, rackets, recasts, restack, restick, retacks, retasks, rickets, sackers, satires, satiric, scatter, seasick, sickest, sitters, skaters, skitter, stacker, staters, statice, statics, sticker, straits, streaks, striate, stricks, strikes, tackers, tackier, taskers, tasters, tastier, tickers, tickets, trickie, trisect, tsarist