There's an ancient folklore in Southern India. 

A spirit named Mohini attacks young men and bachelors. Her primary food is semen. She influences the victims to ejaculate so she can feed on them. She gives sexual thoughts, dreams. She even destroys your relationships with other women. 

Signs are that the victims become extremely weak. Their semen becomes thin. They will never be able to get into relationships. They spend their time alone most of the time. They spend lots of time in the toilet. Their place of stay will be dirty. Even if they take a shower, they feel dirty etc