Your wife has more chances of catching salmonella from cooking your dinner, than from a reptile, short of cooking an omelette with its feces. Cats, various birds, dogs even cause more cases of salmonella, than snakes. Cut pieces of cantelope are just LOADED with salmonella. http://www.doh.wa.gov/Publicat/2002_News/02-77.htm
Reptiles are targetted enough. To say a pregnant woman can't handle a snake, is to say, neither can she own a cat or dog. As long as she properly washes her hands before touching any mucus membranes and doesn't clean out kitty's litter box, there's very low risk to the baby. Tell your wife not to ride the bus or touch door knobs.
I am NOT saying it's fine ok and dandy to lick kiss or heck eat snake poop, but with proper handling and hand washing there's not much to worry about.
It would be far better for you to emphasize that pregnant women should wash their hands thoroughly after handling reptiles than to completely ban their handling. For someone who is in it for the education, I'm really quite surprised by this anti-reptile sentiment.
I don't see how there is even a debate about this. Reptiles have salmonella, fact, handling reptiles always passes on salmonella, NOT TRUE. Wash your hands immediately, how hard is that?