When parents let blood (and therefore they are weakened) before the intercourse with which they conceive their child - although this may be remedied by eating after letting blood: Niddah 17a
Rabbi Yosi reporting that an elder of Jerusalem told him about twenty-four different varieties of the disease called ra'atan: Ketuvot 77b
There are 24 kinds of shechin; the worst is called ra'atan ראתן, and involves a brain parasite: Ketuvot 76b, Niddah 17a
Abbaye's prescription for the neurosurgery needed to remove the parasite that causes ra'atan: Ketuvot 77b
Physical contact causes the skin to deterioriate, and intercourse is especially bad for people with this disease: Ketuvot 77a-b
This disease could cause limbs to fall off: Rashi Keritot 15b "mukei shechin"
The ra'atan variety is characterized by fluids from the eyes, nose and mouth, and flies hover about him: Ketuvot 77b
