The versatile 19-year-old, who had temporary stints at Dorchester Town and Chippenham Town last season, can play left-back or centre-half and may be drafted straight in for Saturday’s home match with league leaders Hemel Hempstead Town (3pm).
The swoop came after Will Spetch yesterday agreed a full-time switch to Sutton United with Dolphins’ backline weakened further by Neil Martin’s groin injury 10 minutes into last night's 3-0 win at Corby Town.
And Killick, who revealed Wannell’s spell would include the play-offs should Poole finish in the top five, was relieved to resolve his selection headache with a host of players faced with fitness tests this weekend.
The Dolphins boss told the Daily Echo: “Jacob is highly thought of and the fact he can play in a couple of positions fits everything we require at the moment. After the events of this week, we are particularly pleased to have him on board.
“Since we took Jacob Jagger-Cane on loan, we have enjoyed a good relationship with Exeter and we are very grateful for their help.”
Meanwhile, Killick admitted Poole had caught midweek opponents Corby at just the right time as goals from Michael Charles and Marvin Brooks along with a Steve Devlin penalty secured a fourth straight league victory.
The result saw Dolphins move to within five points of the Southern League Premier Division play-off places with up to eight games in hand after several Corby players boycotted the fixture, allegedly over unpaid wages.
Killick said: “They certainly had a weakened side out. I would estimate they were without five or six of their main players from the last time we faced them.
"We might have had some fortune but just had to do the job.”
Killick is hoping key quartet Carl Pettefer, Richard Gillespie, Dan Cann and Jordan Chiedozie may be fit enough to feature against Hemel.
Dolphins: (from) Thomas, Muleba, Wannell, Dibba, Whisken, Brooks, Davies, Devlin, Charles, Preston, Elliott, Pettefer, Gillespie, Cann, Chiedozie, Davis, Lowes, Morgan.