The economic consequences of failing to effectively control rodent species attacking crops or stored foodstuffs will probably be readily apparent both at the level of the individual farmer and to agricultural authorities. The disease is seasonal in occurrence and natural infections are usually found among agricultural workers in corn and wheat fields, coinciding with the harvest period. Rodents share men's dwellings and consume or foul part of his food both in the fields before it is harvested and in his granaries and warehouses after it has been processed and stored. One of the serious consequences of this accumulation of uncollected and untreated wastes is the production of conditions that greatly favor the multiplication of rodent populations and lead to greatly increased contacts between rodents and man. Pulex irritans, the human flea, has a global distribution, and is often found in very high densities, is thought by a number of workers to occasionally transmit plague among human populations.