ABSTRACT
Where prevalence of geohelminths and schistosomes is high, co-infections with multiple parasite species are common. Previous studies have shown that the presence of geohelminths either promotes or is a marker for greater prevalence and intensity of Schistosoma mansoni infections. Some of this apparent synergy may simply represent shared conditions for exposure, such as poor sanitation, and may not suggest a direct biologic interaction. We explored this question in a study of 13,279 school children in Jequié, Bahia, Brazil, with a survey of demographic characteristics and stool examinations. Cross-sectional analysis revealed a statistically significant increase in the prevalence and intensity of S. mansoni infection with increasing numbers of geohelminth species (OR 2.5, 95% CI 1.38-3.64). Less than 20% of the strength of this association was contributed by socioeconomic status or environmental conditions. Thus, polyparasitism itself, as well as intrinsic host factors, appears to produce greater susceptibility to additional helminth infections.
Subject(s)
Nematode Infections/epidemiology , Nematode Infections/parasitology , Schistosomiasis/epidemiology , Schistosomiasis/parasitology , Adolescent , Age Factors , Ancylostomatoidea , Animals , Ascariasis/epidemiology , Ascariasis/parasitology , Ascaris lumbricoides/growth & development , Brazil/epidemiology , Child , Cross-Sectional Studies , Feces/parasitology , Female , Hookworm Infections/epidemiology , Hookworm Infections/parasitology , Humans , Male , Parasite Egg Count , Sex Factors , Socioeconomic Factors , Trichuriasis/epidemiology , Trichuriasis/parasitology , Trichuris/growth & developmentABSTRACT
A survey was carried out to determine values for the prevalence and intensity of infection of intestinal helminths in children living in Cocle Province, Republic of Panama. The data set consisted of the results of microscopic examinations (modified Kato Katz technique) of stool samples collected in November 1987 from 661 children attending primary schools in 4 communities in the province. The overall prevalences of Ascaris lumbricoides, hookworm and Trichuris trichiura infections were found to be 18.2, 12.0 and 27.5% respectively. There were significant differences between the infection prevalence values for children attending the different schools, but not with respect to age or sex. Positive associations were detected between particular pairs of infections and these were most evident when Trichuris trichiura was involved. The data revealed evidence of a positive association between siblings at one school only for each helminth infection. There was extreme variation in the values for intensity of infection (20-126180 epg for A. lumbricoides). Highly significant, and unexplained, differences were observed in the intensity of A. lumbricoides infection by primary school; this finding did not apply to hookworm or T. trichiura. The analysis also revealed that children heavily infected with A. lumbricoides were also likely to be heavily infected with T. trichiura. Comparisons with the results of surveys carried out in Cocle Province in 1926 and 1974 indicate that these infections are declining in this region of Panama.
Subject(s)
Ascariasis/epidemiology , Hookworm Infections/epidemiology , Trichuriasis/epidemiology , Analysis of Variance , Ancylostomatoidea/growth & development , Animals , Ascariasis/parasitology , Ascaris/growth & development , Chi-Square Distribution , Child , Feces/parasitology , Female , Hookworm Infections/parasitology , Humans , Intestinal Diseases, Parasitic/epidemiology , Intestinal Diseases, Parasitic/parasitology , Male , Panama/epidemiology , Parasite Egg Count , Prevalence , Trichuriasis/parasitology , Trichuris/growth & developmentABSTRACT
Population dynamical parameters of Trichuris trichiura infections in children were estimated from longitudinal intensity and prevalence data from a population (n = 23) in a children's home in Jamaica. The theoretical predictions of a deterministic model incorporating these parameters were approximated to observed horizontal-age prevalence data from a naturally infected population (n = 203) of children in a St. Lucian village, and a rough estimate of the basic reproductive rate (Ro = 8-10) of T. trichiura obtained. The findings suggest that T. trichiura populations are intrinsically more difficult to control by traditional mass-treatment chemotherapy (eradication requires greater than 91% of the population to be treated every 6 months for greater than 5 years) than are populations of Ascaris, but may be more susceptible to selective chemotherapy programmes which aim to treat only the most heavily infected individuals.
Subject(s)
Trichuriasis/drug therapy , Age Factors , Child , Child, Preschool , Feces/parasitology , Female , Humans , Infant , Jamaica , Male , Mebendazole/therapeutic use , Models, Biological , Parasite Egg Count , Population Dynamics , Recurrence , Trichuriasis/epidemiology , Trichuriasis/parasitology , Trichuris/growth & development , West IndiesABSTRACT
Population dynamical parameters of Trichuris trichiura infections in children were estimated from longitudinal intensity and prevalence data from a population (n=23) in a children's home in Jamaica. The theoretical predictions of a deterministic model incorporating these parameters were approximated to observe horizontal-age prevalence data from a naturally infected population (n=203) of children in a St. Lucian village, and a rough estimate of the basic reproductive rate (Ro=8-10) of T. trichiura obtained. The findings suggest that T. trichiura populations are intrinsically more difficult to control by traditional mass-treatment chemotherapy (eradication requires >91 percent of the population to be treated every 6 months for >5 years) than are populations of Ascaris, but may be more susceptible to selective chemotherapy programmes which aim to treat only the most heavily infected individuals (AU)