Usage of macrons in Latin loanwords

Solution 1:

In §11.94, Diacritics—specialized versus general contexts, the Chicago Manual of Style advises (emphasis mine):

Nearly all systems of transliteration require diacritics—including macrons, underdots, and overdots, to name just a few. Except in linguistic studies or other highly specialized works, a system using as few diacritics as are needed to aid pronunciation is easier on readers, publisher, and author.

...

For nonspecialized works, the transliterated forms without diacritics that are listed in any of the latest editions of the Merriam-Webster dictionaries are usually preferred by readers and authors alike.

In general, it's not necessary to italicize or apply macrons to foreign words that have been transliterated and absorbed into English.

Solution 2:

They weren’t used even in Latin. They are used in books for those studying Latin to help them identify, for example, the ablative ending in the singular of the first declension, and they can also be helpful in scanning Latin verse. They serve no purpose when Latin words are used in English (and Latin words in English are mostly best avoided anyway).