In 1666 Jesuit Bark was used as a prevention against what

Malaria
Jesuit's Bark, also called Peruvian Bark, is the historical name of the most celebrated specific remedy for all forms of malaria.

It is so named because it was obtained from the bark of several species of the genus Cinchona, of the Rubiaceae family, that have been discovered at different times and are indigenous in the Western Andes of South America and were first described and introduced by Jesuit priests who did missionary work in Peru.

Other terms referring to this preparation and its source were "Jesuit's Tree", "Jesuit's Powder" and "Pulvis Patrum".

Read more...https://en.wikipedia.org/wiki/Jesuit%27s_bark