Helminth Infection and Cognitive Impairment Among Filipino Children

Abstract

The objective of this study was to examine the independent effect of infection with each of four helminths (Ascaris lumbricoides, Schistosoma japonicum, Necator americanus, and Trichuris trichiura) on cognitive function after adjusting for the potential confounders nutritional status, socioeconomic status (SES), hemoglobin, sex, and the presence of other helminthes. This cross-sectional study was carried out in a rural village in Leyte, The Philippines in 319 children 7-18 years old. Three stools were collected and read in duplicate by the Kato Katz method. Infection intensity was defined by World Health Organization criteria. Cognitive tests were culturally adapted and translated. Learning and memory cognitive domains were each defined by three subscales of the Wide Range Assessment of Memory and Learning, which had an inter-rater reliability >/= 0.92 and test-retest reliabilities ranging from 0.61 to 0.89. A household SES questionnaire was administered. A logistic regression model was used to quantify the association between performance in different cognitive domains (learning, memory, verbal fluency, and the Philippine Non-Verbal Intelligence Test) and helminth infections. After adjusting for age, sex, nutritional status, hemoglobin, and SES, S. japonicum infection was associated with poor performance on tests of learning (odds ratio [OR] = 3.04, 95% confidence interval [CI] = 1.1-6.9), A. lumbricoides infection was associated with poor performance on tests of memory (OR = 2.2, 95% CI = 1.04-4.7), and T. trichiura infection was associated with poor performance on tests of verbal fluency (OR = 4.5, 95% CI = 1.04-30). Helminth infection was associated with lower performance in three of the four cognitive domains examined in this study. These relationships remained after rigorous control for other helminths and important confounding covariates.

Effect of Deworming on Indices of Health, Cognition, and Education Among Schoolchildren in Rural China: A Cluster-Randomized Controlled Trial

“…[1][2][3] Observational studies have found that chronic infection with STHs among school-aged children is associated with malnutrition and impaired growth, 4-6 cognitive impairment, 7,8 and lower school attendance. 9 These associations suggest that, in theory, reducing STH infection in children has the potential to improve nutrition and growth (i.e., hemoglobin levels, weight, height), cognitive abilities (i.e., working memory, processing speed), and school performance (i.e., school attendance, standardized test scores).…”

Impact of Polyparasitic Infections on Anemia and Undernutrition among Kenyan Children Living in a Schistosoma haematobium-Endemic Area

“…1 However, it was not until recently that the combined detrimental effects of polyparasitism on childhood growth and development have emerged as a research focus. [2][3][4][5][6] The relationship between parasitic helminths and the subtle morbidities of undernutrition and anemia has been increasingly recognized in the past 20 years. 4,6 Previous studies have examined the overlapping effects of infection by soil-transmitted helminths (STHs), including hookworm, Ascaris lumbricoides, and Trichuris trichiura, on these outcomes, and more recently, studies have examined the combined effects of STH with schistosomiasis.…”

Herd immunity acquired indirectly from interactions between the ecology of infectious diseases, demography and economics

“…However, over the relevant economic time (i.e. intergenerational time), the transmission rate is determined by this feedback between economics and epidemiology and is thus endogenous to the system (Nokes et al 1992;Holding & Snow 2001;Ezeamama et al 2005;Fernando et al 2006). We can build such feedbacks into our model system by making the transmission rate a function of income and income a function of health:…”

“…This is due to both (i) a direct effect of health on labour productivity and, perhaps more importantly, (ii) an indirect effect on labour productivity through the effect of childhood health on the acquisition of human capital-the training and education of the workforce. Diseases such as malaria and parasitic worms, among others, are known to directly interfere with childhood learning processes, and therefore ultimately undermine long-term economic success (Nokes et al 1992;Holding & Snow 2001;Ezeamama et al 2005;Fernando et al 2006). …”