YOU SAID:

the man has lost his dog to a sickness that made the dog sad

INTO JAPANESE

その男は、犬を悲しませた病気で犬を失った

BACK INTO ENGLISH

The man lost his dog to a disease that made him sad

INTO JAPANESE

その男は、彼を悲しませた病気で犬を失った

BACK INTO ENGLISH

The man lost his dog to a disease that made him sad