Intestinal parasitic infestation among different population groups of Andaman and Nicobar islands.

A survey was carried out among the rural and urban settlers and two tribal groups viz. Nicobarese and Onges, of Andaman and Nicobar islands. The survey covered preschool school aged children and adults. Out of the total 1,384 stool samples examined, 652 (47.1%) showed ova or cysts of one or more intestinal parasites. Among the preschool children, Nicobarese showed the highest overall prevalence rate (80.5%) followed by urban (46.7%) and rural (38.6%) preschool children. Ascaris lumbricoides was the commonest form of parasite encountered in all the groups of preschool children, followed by Trichuris trichura. While ascariasis and trichuriasis were more common among the urban children than in rural children, giardiasis was more common among the rural preschool children. The school age children among rural settlers showed an overall prevalence rate of 61.1% which was significantly higher than that among the rural preschool children. Among the school age children also, ascariasis was the commonest form of parasitosis followed by trichuriasis. The Nicobarese and Onge adults showed significantly higher overall prevalence rates (72.2%) and 71.1% vs 48.6%) compared to rural adults. In all the groups studied ascariasis was the commonest form of parasitosis except in Onges among whom trichuriasis and giardiasis were more common than ascariasis. Change in prevalence rates over age was studied among the rural settlers. While ascariasis and trichuriasis showed peak prevalence rates in school age children prevalence of giardiasis declined with increase in age from a peak in the preschool age group and prevalence rates of hook worm infestation continued increasing beyond school age.