Population biology of hookworms in children in rural West Bengal. I. General parasitological observations.

Hookworm infection was studied over a 22-month period in 31-49% of a population of 1,803 1- to 10-year-old children in a rural area near Calcutta where both Necator americanus and Ancylostoma duodenale were prevalent. Half of the children were infected before age 5 and 90% were infected by age 9, when the mean egg count reached 2,000 eggs/g of feces. Infection was significantly heavier and more prevalent among males than among females, and greater among Muslims than among Hindus. These differences were apparent in children less than 2 years of age. Numerical factors were devised to adjust fecal egg counts for both the smaller fecal output of children and the increased dilution of eggs in watery feces as compared to formed feces. It is proposed that egg counts from 1- to 3-year-olds be multiplied by 0.3, those from 4- to 6-year-olds by 0.5, those from 7- to 9-year-olds by 0.6, and those from 10 to 12-year-olds by 0.7; differences in mean egg density among various fecal consistencies produced factors of 1, 1.5, 2, 3, and 3.5 by which the egg counts in formed, mushy-formed, mushy, mushy-diarrheic, and diarrheic feces should be increased.