From IvanWiki

Leprosy

This state will abuse player's stats over time, and, most importantly, cause limbs to drop off one by one in random intervals.

The message indicating being infected is "You feel you're falling in pieces."

You can get leprosy from the following sources:

• Eating leprosy-infected meat.
• Being near a monster that has leprosy (such as a Zombie)
• Putting back a bodypart that is infected (see below).

Leprosy can be cured with drinking antidote liquid, with a divine intervention from Seges, or by the Priestess in New Attnam.

Actually, leprosy is not a player disease on the whole. Single limbs are infected by leprosy: that means that reattaching an infected limb (such as one which dropped down due to leprosy) also infects the player completely.

Lycanthropy

A state where you turn into a Werewolf occasionally. Eating werewolf flesh certainly will, or a magic effect from a fountain may cause this. The message indicating that player got infected with lycanthropy is "You notice you've always liked full moons."

Parasites

If you see the message "Ugh. You feel something violently carving its way through your intestines." you have been infiltrated by a parasite. Every time this message appears, you lose some HP.

Right now (as in IVAN 0.50) there are two types of parasites :

• Tapeworms,
• Broad tapeworms;

The latter being more difficult to get rid off by means of vomit.

You can get contaminated by multiple reasons:

• Eating spoiled food
• Kobolts and Goblins might have them, so don't eat them if they're rotten.
• Drinking from a fountain may cause this.
• Eating a Black Unicorn corpse

You can get rid of parasites by:

• Vomiting until the game says that you notice the dead parasite in the vomit
• Drinking antidote liquid
• Ultimately, if the previous won't help, by drinking Sulphuric acid. This'll kill you though, if you don't have a strong acid resistance