The word rickettsiosis 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: 20
Highest Scoring Words With Friends™ Plays In The Letters
Seven Letter Word Alert: (40 words)
corsets, cosiest, cotters, crosses, erotics, escorts, ketosis, ketotic, kissers, kitties, oecists, oikists, resists, restick, restock, rickets, rockets, rosiest, scissor, sectors, sickest, sissier, sisters, sitters, skitter, sockets, sorties, sticker, stocker, stokers, stories, stricks, strikes, strokes, tickers, tickets, tossers, trickie, tricots, trisect