Today’s first glitch:
Change the comma after livestock to a period.
Add a comma after horror.
Change the period after word to a colon. (A comma would also work, although the colon gives the word after it greater emphasis/significance, which you may want here.)
When referring to a word as the word itself, italicize it. Here, italicize infected.
For the first time, mankind can hear the thoughts of livestock. To our horror, every creature is found to be thinking one word: infected.