Control of intestinal nematode infections by chemotherapy: mass treatment versus diagnostic screening.

There is increasing interest in the implementation of programmes to control nematodiases by chemotherapy, but no consensus on whether diagnostic screening before treatment is an essential component of such programmes. It is estimated that a screening component increases costs by a factor of 2-6 and may be beyond the economic and skill resources of endemic areas, but accords with accepted medical practice since only infected individuals are treated. In an attempt to examine this issue quantitatively, the relative risks of mass treatment and morbidity due to helminthiasis are compared. Age- and locality-targeting of mass treatment at populations at high risk of morbidity are proposed as procedures for further enhancing this risk differential. It is suggested that resolving the question of screening versus mass treatment requires more quantitative information than is currently available on the risk of side effects with treatment and the risk of morbidity with variable intensities of infection.