Replacement patterns of Ascaris lumbricoides populations in Filipino children.

The replacement patterns of Ascaris lumbricoides worm populations were investigated by complete deworming of 150 Filipino children (0-14 years old) from both urban and rural barangays and analyzing the age distribution of the 2,072 adult worms (939 males and 1,133 females) obtained, based on Seo's (1983) regression equation relating length to age. It was observed that most worm populations followed a periodic pattern of replenishment. This supports the general practice of periodic anthelminthic campaigns. However, there seems to be a tendency for moderate and heavy cases to follow a continuous replacement pattern as evidenced by shorter time intervals between generations and wider age ranges. The data suggest that periodic deworming schedules may not be appropriate in areas where cases are predominantly of higher intensity. In such situations, control and/or eradication can probably be achieved only if chemotherapy is applied more frequently and supplementary health education and environmental modification measures are provided.