Assessment of the effectiveness of primary health care interventions in the control of three intestinal nematode infections in rural communities.

In a 30 months' longitudinal study, primary health care intervention was effective in reducing the prevalence of three common intestinal nematode infections (Ascaris lumbricoides, Trichuris trichiura and Necator americanus) in three communities. This was achieved by training school leavers and auxiliary aides as microscopists, health inspectors and field assistants and deploying them to provide screening, surveillance, environmental sanitation, and mass-expulsion chemotherapy (MEC). Post-control surveillance confirmed that the prevalence of these infections had been greatly reduced. The prevalence of Ascaris lumbricoides had declined from 49.3% (pre-intervention) to 10.5% (post-intervention). Hookworm had fallen from 31.4% (pre-intervention) to 4.1% (post-intervention) and whipworm from 40.7% (pre-intervention) to 6.5% (post-intervention). Overall percentage decreases of 78.7%, 86.9% and 84.0% were recorded for Ascaris lumbricoides, Necator americanus and Trichuris trichiura respectively. The initial decline in prevalence was due to the MEC campaign, but the improved sanitation and health education presumably reduced the reinfection rate. If the entire population participated, periodic repetition of the mass expulsion therapy campaign at appropriate intervals combined with continued attention to environmental hygiene and prolonged health education could bring these infections under control within a few years.