Marsilio Ficino lived from October 19, 1433 to October 1, 1499. John Aberth, a history professor at the University of Vermont, identifies Ficino as a medieval thinker in his book An Environmental History of the Middle Ages: The Crucible of Nature (2012). This is a common labeling error which I have come to believe enables scholars to downplay the contributions of earlier thinkers to modernity. But that is not the topic of discussion today.
This Italian philosopher is credited with helping revive the knowledge of the ancients, for instance he translated Plato into the universal scholarly language of the time, Latin. He wrote "the Whole, in which 'we live and move and have our being,' is itself alive," and strove to combine Christianity and Platonism.
In 1481 Ficino addressed the causes of the plague and noted animals and people can have the same diseases. His work, Consiglio Contro la pestilenza , asserts that the presence of hawks indicate an area which is healthier because hawks fly away from poisoned air. This argument echoed a common sentiment of the time. Ficino pointed to evidence though, that some contaigion,( to use modern language) does not pass between men and animals. "A cat and dog have brought the plague from home to home without being sick themselves." Bad example, but not inappropriate principles. Although actually cats were a protection against the plague, it is not inaccurate to suggest that men and the other animals can have different vulnerabilities.
Elsewhere Marsilio Ficino said, "Nature is everywhere a magician." By this he meant that things were interconnected. This was a helpful tenet in a world where people thought that saying a god willed something, was a kind of explanation.