Chisholm, "Surgeon to his Majesty's Ordnance in Grenada," was apparently the first to observe the mode of transmission of the Guinea worm, Dracunculus medinensis. Chishom was also one of the first to recognize that the yellow fever epidemic of 1793-1794 was caused by some factor brought to the western hemisphere by the Hankey, a ship that had sailed from the west coast of Africa. However, like the rest of his medical peers, Chisholm did not understand that mosquitoes were vectors of the disease. Digital facsimile of the 1795 edition from the Internet Archive at this link. 

In 1801 Chisholm, by then "Inspector-General of the Ordnance Medical Department in the West Indies," issued from London a greatly expanded second edition in two volumes as: An essay on the malignant pestilential fever introduced into the West Indian islands from Boullam, on the coast of Guinea, as it appeared in 1793, 1794, 1795, and 1796. Interspersed with observations and facts, tending to prove that the epidemic existing at Philadelphia, New-York, &c. was the same fever introduced by infection imported from the West India Islands: And illustrated by evidences founded on the state of those islands, and the information of the most eminent practiioners residing on them. 

Digital facsimile of the second edition from the Internet Archive at this link.