Decision-Model Estimation of the Age-Specific Disability Weight for Schistosomiasis Japonica: A Systematic Review of the Literature

Schistosomiasis is among the most prevalent parasitic infections worldwide. However, current Global Burden of Disease (GBD) disability-adjusted life year estimates indicate that its population-level impact is negligible. Recent studies suggest that GBD methodologies may significantly underestimate the burden of parasitic diseases, including schistosomiasis. Furthermore, strain-specific disability weights have not been established for schistosomiasis, and the magnitude of human disease burden due to Schistosoma japonicum remains controversial. We used a decision model to quantify an alternative disability weight estimate of the burden of human disease due to S. japonicum. We reviewed S. japonicum morbidity data, and constructed decision trees for all infected persons and two age-specific strata, <15 years (y) and ≥15 y. We conducted stochastic and probabilistic sensitivity analyses for each model. Infection with S. japonicum was associated with an average disability weight of 0.132, with age-specific disability weights of 0.098 (<15 y) and 0.186 (≥15 y). Re-estimated disability weights were seven to 46 times greater than current GBD measures; no simulations produced disability weight estimates lower than 0.009. Nutritional morbidities had the greatest contribution to the S. japonicum disability weight in the <15 y model, whereas major organ pathologies were the most critical variables in the older age group. GBD disability weights for schistosomiasis urgently need to be revised, and species-specific disability weights should be established. Even a marginal increase in current estimates would result in a substantial rise in the estimated global burden of schistosomiasis, and have considerable implications for public health prioritization and resource allocation for schistosomiasis research, monitoring, and control

Prevalence of and factors associated with human cysticercosis in 60 villages in three provinces of Burkina Faso

Background : Taenia solium, a zoonotic infection transmitted between humans and pigs, is considered an emerging infection in Sub-Saharan Africa, yet individual and community-level factors associated with the human infection with the larval stages (cysticercosis) are not well understood. This study aims to estimate the magnitude of association of individual-level and village-level factors with current human cysticercosis in 60 villages located in three Provinces of Burkina Faso. Methodology/Principal Findings : Baseline cross-sectional data collected between February 2011 and January 2012 from a large community randomized-control trial were used. A total of 3609 individuals provided serum samples to assess current infection with cysticercosis. The association between individual and village-level factors and the prevalence of current infection with cysticercosis was estimated using Bayesian hierarchical logistic models. Diffuse priors were used for all regression coefficients. The prevalence of current cysticercosis varied across provinces and villages ranging from 0% to 11.5%. The results obtained suggest that increased age, being male and consuming pork as well as a larger proportion of roaming pigs and percentage of sand in the soil measured at the village level were associated with higher prevalences of infection. Furthermore, consuming pork at another village market had the highest increased prevalence odds of current infection. Having access to a latrine, living in a household with higher wealth quintiles and a higher soil pH measured at the village level decreased the prevalence odds of cysticercosis. Conclusions/Significance : This is the first large-scale study to examine the association between variables measured at the individual-, household-, and village-level and the prevalence odds of cysticercosis in humans. Factors linked to people, pigs, and the environment were of importance, which further supports the need for a One Health approach to control cysticercosis infection

Assessing the Impact of Misclassification Error on an Epidemiological Association between Two Helminthic Infections

Hookworm, roundworm, and whipworm are collectively known as soil-transmitted helminths. These worms are prevalent in most of the developing countries along with another parasitic infection called schistosomiasis. The tests commonly used to detect infection with these worms are less than 100% accurate. This leads to misclassification of infection status since these tests cannot always correctly indentify infection. We conducted an epidemiological study where such a test, the Kato-Katz technique, was used. In our study we tried to show how misclassification error can influence the association between soil-transmitted helminth infection and schistosomiasis in humans. We used a statistical technique to calculate epidemiological measures of association after correcting for the inaccuracy of the test. Our results show that there is a major difference between epidemiological measures of association before and after the correction of the inaccuracy of the test. After correction of the inaccuracy of the test, soil-transmitted helminth infection was found to be associated with increased risk of acquiring schistosomiasis. This has major public health implications since effective control of one worm can lead to reduction in the occurrence of another and help to reduce the overall burden of worm infection in affected regions

Global research priorities for infections that affect the nervous system

Infections that cause significant nervous system morbidity globally include viral (for example, HIV, rabies, Japanese encephalitis virus, herpes simplex virus, varicella zoster virus, cytomegalovirus, dengue virus and chikungunya virus), bacterial (for example, tuberculosis, syphilis, bacterial meningitis and sepsis), fungal (for example, cryptococcal meningitis) and parasitic (for example, malaria, neurocysticercosis, neuroschistosomiasis and soil-transmitted helminths) infections. The neurological, cognitive, behavioural or mental health problems caused by the infections probably affect millions of children and adults in low- and middle-income countries. However, precise estimates of morbidity are lacking for most infections, and there is limited information on the pathogenesis of nervous system injury in these infections. Key research priorities for infection-related nervous system morbidity include accurate estimates of disease burden; point-of-care assays for infection diagnosis; improved tools for the assessment of neurological, cognitive and mental health impairment; vaccines and other interventions for preventing infections; improved understanding of the pathogenesis of nervous system disease in these infections; more effective methods to treat and prevent nervous system sequelae; operations research to implement known effective interventions; and improved methods of rehabilitation. Research in these areas, accompanied by efforts to implement promising technologies and therapies, could substantially decrease the morbidity and mortality of infections affecting the nervous system in low- and middle-income countries

Is bisphenol-A exposure during pregnancy associated with blood glucose levels or diagnosis of gestational diabetes?

Recent epidemiological studies indicate bisphenol A (BPA), an estrogenic chemical used in production of epoxy, polycarbonate, and plastic may increase risk of insulin resistance and type 2 diabetes. Exposure to BPA during pregnancy may contribute to development of gestational diabetes mellitus (GDM), a precursor to type 2 diabetes in women. This pilot study examined the association between BPA exposure, fasting blood glucose levels (FBG), and GDM diagnosis during pregnancy. Banked urine samples from 22 cases of GDM and 72 controls were analyzed for total (free BPA + conjugates) urinary BPA concentrations (μg/L). FBG levels (mg/dl) were obtained from 1-h 50-g glucose tolerance tests (GTT) that women underwent for routine GDM screening (mean gestational age = 26.6 weeks, SD = 3.8). Those with an initial screening value ≥ 135 mg/dl underwent 3-h 100 g oral GTT. GDM diagnoses were made when the initial screening value was ≥ 200 mg/dl or when values at ≥ 2 time points exceeded 3-h oral GTT thresholds. Among controls, median FBG levels (mg/dL) did not differ across exposure tertiles, defined according to the distribution of total specific-gravity-adjusted urinary BPA concentrations. Logistic regression models controlling for race/ethnicity did not provide evidence of association between BPA exposure and case status across increasing tertiles of BPA exposure (number of GDM cases/controls in tertile1: 13/24; in tertile 2: 6/24; in tertile 3: 3/24). Findings do not support a relationship between total urinary BPA concentrations and altered glucose metabolism during pregnancy. However, due to study limitations, findings need to be interpreted with caution

Urinary phthalate metabolite concentrations and blood glucose levels during pregnancy

Purpose: To examine associations between phthalate metabolite urinary concentrations during early pregnancy and blood glucose levels obtained at the time of screening for gestational diabetes mellitus (GDM). Methods: Upon initiation of prenatal care, women with a mean gestational age of 12.8 weeks were recruited for a study of environmental chemical exposures (n = 110) and provided a spot urinary specimen. Blood glucose concentrations (mg/dl) were obtained from the electronic medical record for those patients who did not experience a pregnancy loss and did not transfer care to another facility prior to glucose screening (n = 72). Urinary concentrations of nine phthalate metabolites and creatinine were measured at the US Centers for Disease Control and Prevention. Associations between tertiles of phthalate metabolites concentrations and blood glucose levels were estimated using linear regression. Results: Compared to pregnant women in the lowest concentration tertile, women with the highest urinary concentrations (≥ 3 rd tertile) of mono-iso-butyl phthalate (tertile: ≥ 15.3 μg/l, β = -18.3, 95% CI: -35.4, -1.2) and monobenzyl phthalate (tertile: ≥ 30.3 μg/l, β = -17.3, 95% CI: -34.1, -0.4) had lower blood glucose levels at the time of GDM screening after adjustment for urinary creatinine and demographic covariates. Conclusion: Because maternal glucose levels increase during pregnancy to provide adequate nutrition for fetal growth and development, these findings may have implications for fetal health. However, given the limitations of our study, findings should be interpreted cautiously

Spatial distribution and populations at risk of A. lumbricoides and T. trichiura co-infections and infection intensity classes: an ecological study.

BACKGROUND: Soil-transmitted helminth (STH) infections are highly prevalent in the Philippines. Mapping the prevalence and high-intensity of STH co-infections can help guide targeted intervention programmes to reduce morbidity, especially among vulnerable school-aged children. In this study, we aimed to predict the spatial distribution of the prevalence of Ascaris lumbricoides and Trichuris trichiura co-infection and infection intensity classes in the Philippines to identify populations most in need of interventions. METHODS: Data on STH infections from 29,919 individuals during the nationwide parasitological survey in 2005 to 2007 were included in the analysis. To geographically predict the prevalence of A. lumbricoides and T. trichiura co-infections and infection intensity classes, Bayesian multinomial geostatistical models were built including age, sex, environmental variables and a geostatistical random effect. The number of individuals co-infected and belonging to each of the infection intensity classes in 2017 was forecast by combining our predictive prevalence maps with population density maps. RESULTS: Our models showed that school-aged children (5-19 years) are most at risk of A. lumbricoides and T. trichiura co-infections and of moderate/high infection intensity compared to other age groups. We identified target provinces where the likelihood of STH-associated morbidity was highest: Luzon (Bulacan, Benguet, Cavite, Sorsogon, Metropolitan Manila, Pampanga and Rizal), the Visayas (Cebu, Iloilo, Leyte and Negros Occidental), and in Mindanao (Agusan Del Norte, Davao Del Sur, Davao Oriental, Lanao Del Sur, Maguindanao, Misamis Oriental, Sulu and Zamboanga Del Sur). Luzon had the highest estimated number of school-aged children with A. lumbricoides and T. trichiura co-infections (estimated total 89,400), followed by the Visayas (38,300) and Mindanao (20,200). CONCLUSIONS: Our study provided epidemiological evidence to highlight national priority areas for controlling co-infections and high intensity infections in the Philippines. Our maps could assist more geographically targeted interventions to reduce the risk of STH-associated morbidity in the Philippines

Monetary impact of Taenia solium cysticercosis in four countries

The societal monetary burden of cysticercosis in the Eastern Cape Province, South Africa, Honduras, India and the United States of America were estimated. Data on the frequency of infection and on associated morbidity in both human and pig populations and their costs were collected. Decision trees were used to assess the frequency of medical care and loss of value of pigs with their monetary impact