The researches of earlier investigators have demonstrated that houseflies (Musca domestica) will, on occasion, feed and breed in human excrement, and may thereby become contaminated with pathogens which the flies may later transmit to man. Howard (1911), Armstrong (1914), and Watt and Lindsay (1948) have shown an apparent correlation between housefly abundance and the incidence of enteric infections. The knowledge of these epidemiological factors was the principal reason underlying the development of the so called sanitary pit privy and the advocacy of its use in unsanitated areas for the prevention of fly-borne diseases.
The plan of construction of this device is based upon the assumption that houseflies will feed and breed in the pit unless barriers are erected to exclude them. Incorporation of such fly-proofing in the plan of construction adds materially to the costs, a pertinent consideration to the low income groups which ordinarily use this privy.