Treatment of Trichuris trichiura infections improves growth, spelling scores and school attendance in some children.

The effects of treating Trichuris trichiura infections were investigated in 407 Jamaican children age 6 to 12 y. The children were randomly assigned to receive treatment (albendazole) or a placebo. The outcome variables included growth, tests of reading, spelling and arithmetic, and school attendance. After 6 mo of treatment, there was no significant main effect on any of the outcomes. However, there were significant treatment-by-infection intensity interactions with spelling (P < 0.05) and body mass index (P < 0.01), and a significant treatment-by-stunting interaction with school attendance (P < 0.01). In spelling, the children with heavy infections showed improvements with treatment that approached significance (P = 0.06), whereas those with lower intensities did not. However, the children with lower infection intensities had increased body mass index with treatment (P = 0.02), although there was no difference in children with heavy infections. In school attendance, the stunted children improved with treatment (P < 0.04), whereas there was no difference in the nonstunted children. These findings suggest that in the sample of Jamaican children examined, the treatment of T. trichiura was more likely to benefit school performance in children of poor nutritional status and those with heavy infections, and to improve weight gain in children with lighter infection intensities.

Trichuris trichiura infection and cognition in children: results of a randomized clinical trial.

The effects of mild to moderate infections of Trichuris trichiura on cognitive functions were investigated in Jamaican children aged 7 to 10 years. In all, 189 infected children and 100 uninfected classmates were studied. The infected children were randomly assigned to receive treatment (albendazole) or a placebo. All children were given cognitive tests on enrolment and 14 weeks later. These included verbal fluency (generation of ideas), digit span (working memory), number choice (speed of processing of visual stimuli), visual search (sustained attention) and a French Vocabulary test (paired-associate learning). At baseline, the infected children had lower scores than the uninfected ones in fluency (P = 0.01), search (P = 0.02) and French (P = 0.01). Treatment effects were examined among infected children and there was no significant treatment effect for any of the tests. However, there was a significant treatment by weight-for-age interaction in fluency (P < 0.05). The children with low weight-for-age (Z-score < -1) improved with treatment while there was no improvement with treatment among the other children. We concluded that treatment of children with mild to moderate T. trichiura infections using albendazole produces little benefit in cognition if they are adequately nourished; however, undernourished children are more likely to benefit.

Iron status of schoolchildren with varying intensities of Trichuris trichiura infection.

The relationship between varying intensities of Trichuris trichiura infection and iron status was examined in Jamaican schoolchildren, aged 7 to 11 years. A total of 409 children was identified with T. trichiura (epg > 1200). A control group comprised 207 uninfected children who were matched by school and class to every pair of infected subjects. Blood samples were obtained from 421 children: 264 infected and 157 controls. Compared to the rest of the children, those with heavy infections (epg > 10,000) had significantly lower (P < 0.05) Hb (11.5 +/- 1.3 vs. 12.1 +/- 1.1 g/dl), MCV (78.6 +/- 6.3 vs. 81.2 +/- 5.5 fl), MCH (26.2 +/- 2.9 vs. 27.5 +/- 2.5 pg) and MCHC (33.2 +/- 1.5 vs. 33.9 +/- 1.4 g/dl). Similarly, the prevalence of anaemia (Hb < 11.0 g/dl) amongst heavily infected children (33%) was significantly higher (P < 0.05) than the rest of the sample (11%). These differences remained significant after controlling for confounding variables including socio-economic status, age, gender, area of residence and the presence of Ascaris infections. Differences in red cell count, ferritin, and free erythrocyte protoporphyrin were not statistically significant and showed no association with the infectious load. These results suggest that in the Jamaican children studied, iron deficiency anemia is associated with Trichuris infections over 10,000 epg, but not with less intense infections.

Geohelminth infections in school-aged children in Jamaica.

There is concern that geohelminthiasis may adversely affect the growth and development of children. The relevance of this in the Caribbean is unclear since in many territories the prevalence of geohelminths is unknown. We report the results of three surveys conducted in Jamaican primary schools located in areas at high risk for geohelminthiasis. The first was conducted in 12 Kingston schools and comprised children in grades 2 to 5 (aged 7 to 10 years). The second and third surveys were conducted in rural areas with children in grades 2 to 5 and grades 4 and 5, respectively. Overall, 9244 children provided stool samples for analysis. The prevalence of Trichuris trichiura ranged from 42% to 47% among the surveys while that for Ascaris lumbricoides ranged from 15% to 37%. Children in grades 2 and 3 had lower T. trichiura prevalences than those in grades 4 and 5 in the first and second surveys (p < 0.05 and p < 0.005, respectively). In the second survey only, children in grades 2 and 3 had a lower prevalence of A. lumbricoides than those in grades 4 and 5 (p < 0.005). Most infections were light with approximately 1% of the sample having heavy egg densities.

The rate of ingestion of Ascaris lumbricoides and Trichuris trichiura eggs in soil and its relationship to infection in two children's homes in Jamaica.

The rate of exposure to geohelminth infection of children living in 2 institutions in Jamaica, West Indies, was estimated from the product of their rates of ingestion of soil and the density of parasite eggs in the environment. The estimated mean rate of egg ingestion was 9-20 Ascaris lumbricoides eggs and 6-60 Trichuris trichiura eggs per year, although the distribution was highly overdispersed so that some individuals had an estimated annual exposure of several hundred eggs. The estimated individual rates of exposure correlated significantly with the observed worm burdens in children at one of the homes, but not at the other. It is suggested that the susceptibility of the children and the distribution of infective stages in the environment may be important in determining the relationship between exposure and the rate of acquisition of infection.

Quantitative assessment of contamination of soil by the eggs of Ascaris lumbricoides and Trichuris trichiura.

This study used a method of retrieving eggs from soil to examine the spatial and temporal dynamics of soil contamination with geohelminth eggs. The level of soil contamination in two children's homes in Jamaica was determined before and after further soil contamination was prevented by chemotherapy. The home which had higher human infection levels also had a higher prevalence and density of eggs in soil. The spatial distribution of the eggs in soil was overdispersed in the home with higher levels of infection, and underdispersed in the other, perhaps due to the low density of eggs. At both localities, the proportion of soil samples containing eggs and the density of eggs in soil declined over a two-month period. The results suggest that geohelminth eggs are rapidly depleted from the surface of tropical soils in the absence of continuing sources of contamination.

Control of geohelminths by delivery of targeted chemotherapy through schools.

This study describes the age-targeted chemotherapeutic control of geohelminthiasis in the total population (n = 11,500) of the island of Montserrat, West Indies. The intervention programme involved the treatment with single dose albendazole of all children aged 2-15 years (approximately 2500) in 4 sequential cycles at intervals of 4 months. Infection status was monitored by an initial coprological survey of an age-stratified sample (11.5%) of the population, and by surveys of smaller samples (4-5%) after 2 and 4 cycles of treatment (7 and 15 months respectively). The programme delivered treatment to greater than 90% of the target population in each cycle, and reduced the prevalence and intensity of Ascaris lumbricoides and Trichuris trichiura infection in the target age-class. A decline in infection was also observed in the 16-25 year age-class, even though less than 4% of adults received treatment. The study demonstrates that chemotherapy targeted only at children can be implemented within an existing health infrastructure, and can achieve an overall reduction in the prevalence and intensity of geohelminth infection.

Quantitative assessment of geophagous behaviour as a potential source of exposure to geohelminth infection.

The most common form of pica, geophagy, has direct adverse nutritional effects and also exposes children to soil-borne infection. Existing methods for assessing geophagy are either inappropriate for field use (radiology) or unreliable (reporting). A new method is described, based on the measurement of soil-derived silica in stools. More than 90% of silica is excreted within one gut transit period of ingestion. The amount excreted is proportional to the amount ingested. Faecal levels of dietary silica (less than 2% dry wt stool) can be distinguished from levels due to geophagy (up to 25% dry wt stool). Studies in 2 children's homes in Jamaica showed that 33% and 66% of children were geophagous, ingesting up to 10 g soil day-1. The geophagy of less than 20% of the children accounted for greater than 60% of the total soil ingested. This overdispersion of exposure to soil-borne infection may contribute to the observed aggregation of geohelminth infection.