“What’s the difference between an epileptic oyster fisherman and a hooker with diarrhea?” (joke)

An off-color spoonerism is:
 
Q: What’s the difference between an epileptic oyster fisherman and a hooker with diarrhea?
A: The oyster fisherman shucks between fits, and ...
 
The joke has been cited in print since at least 1983. “Epileptic cornhusker” is sometimes used instead of “epileptic oyster fisherman.”
 
     
Google Books
Maledicta
Volumes 6-7
1983
Pg. 32:
What’s the difference between an epileptic oysterman and a whore with diarrhea? — One shucks between fits.
 
Google Books
Maledicta
Volume 8
1985
Pg. 96:
The development of the linguistic concept behind the shits is suggested by the spooneristic conundrum, “What’s the difference between an epileptic oyster shucker and a prostitute with diarrhea? The epileptic oyster shucker shucks between fits, and the prostitute fucks between shits.”
 
Google Books
More the Official Doctors Joke Book
By Larry Wilde
New York, NY: Bantam Books
1986
Pg. 83:
What’s the difference between an epileptic cornhusker and a hooker with diarrhea?
An epileptic corn husker shucks between fits!
 
Google Books
Dr. Speedy’s Jokes and Riddles
By Higino Gonzalez
Lincoln, NE: iUniverse.com, Inc.
2000
Pg. 203:
Q: What is the difference between an epileptic oyster shucker and a whore with the runs?
A: One shucks between fits and the other fucks between shits.
 
Twitter
e0n the ne0 Kore0n
‏@Syndicate0n
One shucks between fits and the other…
12:52 PM - 22 Nov 2008
 
Twitter
ʇɐɥs sɐ ʇɹɐɯs
‏@smartasshat
What’s the difference between an epileptic oyster worker and a nympho with diarrhea?
One of them shucks between fits.
9:56 AM - 15 Jan 2009
 
Twitter
Catherine
‏@BigBadBraid
What’s the difference between an epileptic corn farmer and a hooker with diarrhea?  An epileptic corn farmer shucks between fits.
4:19 PM - 27 Mar 2009