Well . . . It's a slow morning here at the Skunk Works, so I tried googling "leprosy" and "parody" and came up with a fair amount of stuff. I randomly selected two of them. For what they're worth:

To the Beatles' "Let It Be."

I was sittin' in Rwanda when a pimpled guy came up to me!
Now I have a disease,
Leprosy!

And everywhere I go people stare and call me friggin' freak!
Please put on a ski mask,
Leprosy!

Leprosy, Leprosy, Leprosy, Leprosy!
Please burn off these lesions, Leprosy!

Now im sittin on the sofa with a shotgun propped up next to me!
Mother Mary wouldn't save me,
Leprosy!

And when my brains are splattered and you have to call an EMT!
Make sure they don't touch me,
Leprosy!

What is this with the Beatles and leprosy? Here's another one, to the tune of "Yesterday."

Leprosy.
That old rotten man just touched my knee.
Now my flesh is falling off of me.
I think he gave me leprosy.

Suddenly
I'm just half the man I used to be.
Bits and pieces coming off of me.
Yes, leprosy came suddenly.

Why'd my arm fall off?
I don't know, no one will say.
I know something's wrong,
'cause my leg just walked away (without me.)

Yesterday,
I could always lounge the time away.
Now my bed is in a slimy way,
Leprosy has ruined my day.

Why did I get cursed
With this rot, I need to hide.
I'm sure I'm diseased
For my spleen fell out my side. (ooooohhhh.)

Leprosy
It really is a drag for me.
All my friends now run away from me.
Oh how I hate this leprosy.

I've read these through, but I haven't tried singing them, so I'm not sure they scan all that well, but give 'em a try of so moved. Fell free to "folk process" them if they need it.

Don Firth