Prevalence of soil-transmitted helminth infections in the rural population of Bali, Indonesia.

The objectives of this cross-sectional study were to identify the prevalence of soil-transmitted helminth infection in the rural population of Bali and its relation to age, gender, and geoclimatic conditions. The subjects of study were derived from four villages of different geoclimatic conditions, namely wet lowland, dry lowland, wet highland and dry highland, by a multistage, stratified random sampling technique, based on age and gender of the target populations. The technique of Kato-Katz thick smear was used to determine presence of worm eggs in stools, and modified Harada Mori fecal culture technique was used to identify the species of hookworm larvae in stools. The data were analysed descriptively as well as statistically using chi2 test. Of 2,394 completely examined and analysed samples, the results showed as follows: The prevalences of Ascaris lumbricoides, Trichuris trichiura, hookworms and Strongyloides stercoralis were 73.7%, 62.6%, 24.5%, 1.6%, respectively. Of 2,082 infected samples, 33.1% were single infections and 66.9% were mixed infections. Among the mixed infections, dualfection was most frequent (47.8%), followed by single infection (33.1%), triplefection (18.3%), and quadrifection (0.8%). A combination of A. lumbricoides and T. trichiura was predominant in dualfection, while in triplefection a combination of A. lumbricoides, T. trichiura, and hookworms was most frequently identified. The prevalence in males was not statistically different, except for hookworms where it was higher in males than in females. The differences of prevalence of infection according to age groups for A. lumbricoides, T. trichiura and hookworms proved to be highly significant, but not with Strongyloides stercoralis. The prevalence of hookworm infection increased steadily with age to reach its maximum (37.7%) in adulthood (> 18 years), while A. lumbricoides and T. trichiura reached the highest prevalence level in elementary school age (77.3% and 70.7% respectively). The highest prevalence of S. stercoralis infection was found also in elementary school age, but it was not statistically significant. In wet highland the prevalence of infection of A. lumbricoides was 87.6%, T. trichiura 82.4%, hookworms 44.5%, and S. stercoralis 3.3%; these were significantly higher compared to the prevalence of infection in other areas (wet lowland, dry highland, dry lowland).