By a combination of a swab sampling method, modern cultural techniques and Vi-phage typing, a survey for enteric organisms has been made of the sewerage system of a town of about 10,000 inhabitants.
The location of typhoid and paratyphoid B carriers by systematic swabbing of sewers in accordance with cultural findings has been proved feasible.
Two paratyphoid B carriers and one typhoid carrier were discovered by this method. Evidence was obtained of the presence of at least six other foci of paratyphoid infection in the town.
Paratyphoid bacilh were repeatedly isolated from a river flowing through the town. The possible role of river pollution in the maintenance of endemic enteric infection in the area is discussed.
The methods used in this survey might be applied with advantage to the elucidation of unsolved enteric outbreaks, to the control of food-handling establishments and to epidemiological studies of other infections in which the causative organism gains access to sewage.
We are indebted to Mr R. W. Pinney and Mr W. E. Coles, who did by far the greater part of the work of laying the sewage swabs and sending them to the laboratory; to Mr L. M. Blanchard, Surveyor, Sidmouth U.D.C., for his assistance with the preparation of maps of the area; to Dr A. Felix for his kindness in typing the enteric strains isolated; and to Mr R. N. Brown and Mr S. Barlow for much assistance in the development of cultural techniques.