Vegan rickettsial fever was a type of disease.
James T. Kirk came down with Vegan rickettsial fever on his first training assignment. He was given medicine which smelled like a mixture of seaweed, formaldehyde and coffee, a local concoction which was all the colonists had had to offer. Years later, in 2269, Kirk relived the delirium of the fever and the smell of the medicine in a hallucination induced by the thought-shield on Organia. (TOS novel: Spock Must Die!)