My first thought was diet. Monastic orders typically progressed from austere origins towards outright decadence when compared to normal folk. Monks could have b

My first thought was diet. Monastic orders typically progressed from austere origins towards outright decadence when compared to normal folk. Monks could have been eating all manner of unhealthy foods (e.g. Mett in Poland and Germany) that other people seldom or never ate. Using poop as fertilizer is certainly a vector for parasites, but one that people outside of monastic orders were also subject to.