Twenty-three votes were cast in the Scriptorium’s first poll. The question was about the 14th century plague popularly referred to as the Black Death. While we commonly think of the rat acting as a host for fleas and the plague bacillus, it was certainly not the only animal that carried the disease. Besides humans and rats, most animals were susceptible to the bacillus and were infested with fleas. There was, however, one exception. These animals actually repelled fleas and humans who lived and worked closely with this species enjoyed some protection from the plague. The choices presented in the poll were pigs, cows, horses and sheep. The correct answer was the horse. From “The Black Death: Natural and Human Disaster in Medieval Europe” by Robert S. Gottfried:

…important as black rats were in the dissemination of plague, it is essential to emphasize that they were not the only secondary carriers. Along the other rodents already mentioned, additional secondary vector hosts included virtually all household and barnyard animals save the horse, whose odor apparently repels even starving blocked fleas.

Since first reading that short paragraph many years ago, I couldn’t help thinking that this little tidbit of knowledge could somehow be turned into a natural flea product. I’m sure it would probably be much less toxic than the chemicals we use to treat our pets today.