Bayesian Methods for Exposure Misclassification Adjustment in a Mediation Analysis: Hemoglobin and Malnutrition in the Association Between Ascaris and IQ.

BACKGROUND: Soil-transmitted helminth infections have been found to be associated with child development. The objective was to investigate hemoglobin levels and malnutrition as mediators of the association between Ascaris infection and intelligence quotient (IQ) scores in children. METHODS: We conducted a longitudinal cohort study in Iquitos, Peru, between September 2011 and July 2016. A total of 1760 children were recruited at 1 year of age and followed up annually to 5 years. We measured Ascaris infection and malnutrition at each study visit, and hemoglobin levels were measured as of age 3. The exposure was defined as the number of detected Ascaris infections between age 1 and 5. We measured IQ scores at age 5 and used Bayesian models to correct exposure misclassification. RESULTS: We included a sample of 781 children in the analysis. In results adjusted for Ascaris misclassification, mean hemoglobin levels mediated the association between Ascaris infection and IQ scores. The natural direct effects (not mediated by hemoglobin) (95% CrI) and natural indirect effects (mediated by hemoglobin) (95% CrI) were compared with no or one infection: -0.9 (-4.6, 2.8) and -4.3 (-6.9, -1.6) for the effect of two infections; -1.4 (-3.8, 1.0) and -1.2 (-2.0, -0.4) for three infections; and -0.4 (-3.2, 2.4) and -2.7 (-4.3, -1.0) for four or five infections. CONCLUSION: Our results are consistent with the hypothesis that hemoglobin levels mediate the association between Ascaris infection and IQ scores. Additional research investigating the effect of including iron supplements in STH control programs is warranted.

Ascariasis and its relationship with selected psycho-neurological symptoms among children and adults in Poland.

Ascariasis is considered a public health problem mostly in tropical countries and thus studies are realized usually in those countries and particularly in children. As a result, there are limitations in the current literature that associate ascariasis with neurological disorders or psychomotor disturbances. AIM: The aim of study was to prove our hypothesis that ascariasis in children and adults is related to selected psycho-neurological symptoms such as hyperactivity, tic disorders and nail biting (onychophagia). MATERIALS AND METHODS: The study was conducted in the Polish cities of Warsaw and Rzeszów but the patients were drawn from across the country. This study included a total of 465 Poles aged between 1 and 80 years old of both sexes divided into one case group and one control group. The association between the presence of ascariasis and the apparition of selected symptoms was presented within the group containing all subjects and according to gender (males and females) and age (children and adults). The study was conducted in Warsaw and Rzeszów between 2016 and 2018. Data were collected using external laboratories for stool analysis to determine the presence of Ascaris lumbricoides eggs, and a special questionnaire designed to determine the presence of the selected symptoms: hyperactivity, onychophagia and tic disorders. The Mann-Whitney U test was then used to determine differences between groups. RESULTS: We have demonstrated that people with ascariasis showed a higher incidence of all the examined symptoms compared to the results obtained in the control group. Here we report that people infected with Ascaris lumbricoides are more likely to present hyperactivity, onychophagia and tic disorders. Most of the studied symptoms were more intense among women and children. CONCLUSIONS: We have demonstrated that people with ascariasis showed a higher incidence of all the examined symptoms compared to the results obtained in the control group. Here we report that people infected with Ascaris lumbricoides are more likely to present hyperactivity, onychophagia and tic disorders. Most of the studied symptoms were more intense among women and children.

Cognitive Performance and Iron Status are Negatively Associated with Hookworm Infection in Cambodian Schoolchildren.

Soil-transmitted helminth (STH) infection has been associated with lower cognitive performance of schoolchildren. To identify pathways through which STH infection might affect school performance, baseline data from a large rice-fortification trial in Cambodian schoolchildren were used to investigate associations between STH infection, micronutrient status, anemia, and cognitive performance. Complete data on anthropometry, cognitive performance, and micronutrient status were available for 1,760 schoolchildren, 6-16 years of age. STH infection was identified using Kato-Katz, whereas cognitive performance was assessed using Raven's Colored Progressive Matrices (RCPM), block design, and picture completion. STH infection was found in 18% of the children; almost exclusively hookwork infection. After adjusting for age and gender, raw cognitive test scores were significantly lower in hookworm-infected children (-0.65; -0.78; -2.03 points for picture completion, RCPM, and block design, respectively; P < 0.05 for all). Hookworm infection was associated with iron status (total body iron), but not with vitamin A and zinc status, nor with inflammation or anthropometry. Body iron was negatively associated with increased intensity of hookworm infection (R = 0.22, P < 0.001). Hookworm infection in Cambodian schoolchildren was associated with lower cognitive performance, an effect most likely mediated through lower body iron. Interventions that are more effective against hookworm infection are needed to contribute to better health and improvement of cognitive performance.

The effect of intervention methods on nutritional status and cognitive function of primary school children infected with Ascaris lumbricoides.

The prevalence rate of ascariasis in primary school children in northern Jakarta, Indonesia varies from 60% to 90%. An association between helminthic infection and educational achievement has long been recognized. This study was carried out in the northern part of Jakarta among primary school children 6-8 years of age. Treatment of ascariasis and health education were used as the interventions. Before the interventions, basic data on socioeconomic status, epidemiology, infection with Ascaris lumbricoides, nutritional status, and cognitive function were collected. After the interventions, only data on infection with A. lumbricoides, nutritional status, and cognitive function were collected. The children were divided into five groups. Group I was given an anthelminthic (mebendazole), group II was provided with health education, group III was given an antihelminthic and provided with health education, group IV was given a placebo (controls), and group V consisted of egg-negative children, who also served as controls. Data from 336 students were analyzed by analysis of covariance. Parasitologic examinations showed a mean prevalence rate of 58.4% for A. lumbricoides infection in the pre-intervention children and a mean prevalence rate of 40.6% in the post-intervention children. Concerning nutritional status, approximately 80% of the children showed good scores in the pre- and post-treatment data, and only a small percentage (0.9-16.2%) showed mild or moderate malnutrition. No significant difference was found between the pre- and post-treatment nutritional status. The results of the cognitive test showed that the group treated with mebendazole showed significant improvement in the Colored Progressive Matrices and Coding test. Children also showed an improvement in their learning ability, concentration, and eye-hand coordination after five months of receiving this intervention.

Toxocara canis and lead alter consummatory behavior in mice.

Ingestion of palatable and unpalatable solutions was measured in adult mice in which had been administered the common parasite of the dog, Toxocara canis alone, or in combination with lead. In addition, response to hot plate and susceptibility to electroconvulsive seizure were also measured. Results from the palatability test indicated that either lead or Toxocara may alter the mouse's mode of interacting with its environment. However, the two agents in combination interacted in their effects on consummatory behavior. Results from the hot plate and ECS measures were less clear with respect to how lead and/or Toxocara influence temperature reactivity and seizure susceptibility. Histological examination of the CNS in parasite infected animals revealed Wallerian Type degeneration of fiber pathways including the corpus callosum, olfactory tract, and cerebellar penduncles.