Republican presidential candidate Ben Carson on Thursday used an extended metaphor about rabid dogs to discuss efforts to vet refugees fleeing the bloody civil war in Syria.

While speaking at a campaign event in Mobile, Alabama, Carson compared the need to screen refugees before they enter the U.S. with the steps a community would take to protect children from rabid dogs.

"If there is a rabid dog running around your neighborhood, you're probably not going to assume something good about that dog. And you're probably going to put your children out of the way," Carson said. "Doesn't mean that you hate all dogs, by any stretch of the imagination. But, you're putting your intellect into motion and you're thinking, how do I protect my children?"

"By the same token, we have to have in place screening mechanisms that allow us to determine who the mad dogs are, quite frankly," Carson continued. "Who are the people who want to come in here and hurt us and want to destroy us? Until we know how to do that, just like it would be foolish to put your child out into the neighborhood knowing that that was going on, it is foolish for us to accept people if we cannot have the appropriate type of screening." 

The famed retired neurosurgeon, who is currently leading in some polls for the GOP presidential nomination, opposes resettling Syrian refugees in the U.S. in the aftermath of the deadly terrorist attacks in Paris because there he believes we are "putting America at risk" by not vetting them thoroughly enough.

The U.S. already has an extensive vetting process for refugees, including several rounds of security clearance checks that typically last 18 to 24 months. The government is also reportedly using a secret program to screen refugees coming from Syria in particular.

Republicans and some Democrats on Capitol Hill have called for a pause in the resettlement process so the government can bolster the clearance process. Senate Democrats, on the other hand, are seeking to put limits on the visa waiver program, under which citizens and nationals of certain countries are able to enter the U.S. without a visa for 90 days or less.