[burzhash]

Попробою ответить на первый вопрос. В "Повести о детях Хурина" говорится, что:
"the wiser were uneasy still <...> and that Morgoth would be given time enough to take counsel against him. "Ever will some new evil be hatched in Angband beyond the guess of Elves and Men," they said. And in the autumn of that year, to point their words, there came an ill wind from the North under leaden skies. The Evil Breath it was called, for it was pestilent"
Получается, Моргот и создал эту болезнь (продвинутый, блин - и биологическое оружие есть).
Слово "pestilent", кажется, можно перевести как "чума".