Estimating and modeling the dynamics of the intensity of infection with Schistosoma japonicum in villagers of Leyte, Philippines. Part II: Intensity-specific transmission of S. japonicum. The schistosomiasis transmission and ecology project

A dynamic model of Schistosoma japonicum transmission is presented that incorporates effects of infection intensity, age, and sex. We use four infection intensity classes to investigate the impact of ecologic changes and public health interventions on the burden of infection within communities. Age- and sex-specific infection data from three disease-endemic villages in the Philippines are used to estimate the parameters of the model. The model gives good qualitative agreement with observed fecal egg counts adjusted for the accuracy of the Kato-Katz examination. Our results suggest that differences in infection burden between villages are caused by differences in both the infection process and the recovery process in humans. We describe the potential impact of mass treatment of all humans on the numbers with high infection. Furthermore, we show that a sudden reduction in snail population size would affect high prevalence and low prevalence communities in different ways. Copyright © 2005 by The American Society of Tropical Medicine and Hygiene.published_or_final_versio

A tagging SNP in INSIG2 is associated with obesity-related phenotypes among Samoans

<p>Abstract</p> <p>Background</p> <p>A genome wide association study found significant association of a sequence variant, rs7566605, in the insulin-induced gene 2 (<it>INSIG2</it>) with obesity. However, the association remained inconclusive in follow-up studies. We tested for association of four tagging SNPs (tagSNPs) including this variant with body mass index (BMI) and abdominal circumference (ABDCIR) in the Samoans of the Western Pacific, a population with high levels of obesity.</p> <p>Methods</p> <p>We studied 907 adult Samoan participants from a longitudinal study of adiposity and cardiovascular disease risk in two polities, American Samoa and Samoa. Four tagSNPs were identified from the Chinese HapMap database based on pairwise <it>r</it>^{<it>2 </it>}of ≥0.8 and minor allele frequency of ≥0.05. Genotyping was performed using the TaqMan assay. Tests of association with BMI and ABDCIR were performed under the additive model.</p> <p>Results</p> <p>We did not find association of rs7566605 with either BMI or ABDCIR in any group of the Samoans. However, the most distally located tagSNPs in Intron 3 of the gene, rs9308762, showed significant association with both BMI (p-value 0.024) and ABDCIR (p-value 0.009) in the combined sample and with BMI (p-value 0.038) in the sample from Samoa.</p> <p>Conclusion</p> <p>Although rs7566605 was not significantly associated with obesity in our study population, we can not rule out the involvement of <it>INSIG2 </it>in obesity related traits as we found significant association of another tagSNP in <it>INSIG2 </it>with both BMI and ABDCIR. This study suggests the importance of comprehensive assessment of sequence variants within a gene in association studies.</p

A cross-sectional study of the prevalence of intensity of infection with Schistosoma japonicum in 50 irrigated and rain-fed villages in Samar Province, the Philippines

BACKGROUND: Few studies have described heterogeneity in Schistosoma japonicum infection intensity, and none were done in Philippines. The purpose of this report is to describe the village-to-village variation in the prevalence of two levels of infection intensity across 50 villages of Samar Province, the Philippines. METHODS: This cross-sectional study was conducted in 25 rain-fed and 25 irrigated villages endemic for S. japonicum between August 2003 and November 2004. Villages were selected based on irrigation and farming criteria. A maximum of 35 eligible households were selected per village. Each participant was asked to provide stool samples on three consecutive days. All those who provided at least one stool sample were included in the analysis. A Bayesian three category outcome hierarchical cumulative logit regression model with adjustment for age, sex, occupation and measurement error of the Kato-Katz technique was used for analysis. RESULTS: A total of 1427 households and 6917 individuals agreed to participate in the study. A total of 5624 (81.3%) participants provided at least one stool sample. The prevalences of those lightly and at least moderately infected varied from 0% (95% Bayesian credible interval (BCI): 0%–3.1%) to 45.2% (95% BCI: 36.5%–53.9%) and 0% to 23.0% (95% BCI: 16.4%–31.2%) from village-to-village, respectively. Using the 0–7 year old group as a reference category, the highest odds ratio (OR) among males and females were that of being aged 17–40-year old (OR = 8.76; 95% BCI: 6.03–12.47) and 11–16-year old (OR = 8.59; 95% BCI: 4.74–14.28), respectively. People who did not work on a rice farm had a lower prevalence of infection than those working full time on a rice farm. The OR for irrigated villages compared to rain-fed villages was 1.41 (95% BCI: 0.50–3.21). DISCUSSION: We found very important village-to-village variation in prevalence of infection intensity. This variation is probably due to village-level variables other than that explained by a crude classification of villages into the irrigated and non-irrigated categories. We are planning to capture this spatial heterogeneity by updating our initial transmission dynamics model with the data reported here combined with 1-year post-treatment follow-up of study participants

Mapping the Risk of Soil-Transmitted Helminthic Infections in the Philippines

The authors thank the regional coordinators, regional directors, provincial health officers, provincial health team leaders, municipal health officers, medical technologists, midwives, and barangay health workers for their commitment, which was key to completing all the phases of the national prevalence survey. We would like to thank Prof. May Lebanan for assisting us in the preparation of the data set.Author Summary Soil-transmitted helminth (STH) infections with A. lumbricoides, T. trichiura and hookworms are endemic in all 80 provinces of the Philippines, but the spatial variation in the prevalence of these infections has not been previously described. This analysis revealed that while A. lumbricoides and T. trichiura infections were widespread and highly endemic, hookworm infections were more circumscribed to smaller foci in the Visayas and Mindanao. The results also suggest that it may be necessary to place greater emphasis on improving the provision of water, sanitation and the promotion of behavioral change for improved hygiene for the control and prevention of STH infections, particularly for hookworm.Yeshttp://www.plosntds.org/static/editorial#pee

Population Genetics of Schistosoma japonicum within the Philippines Suggest High Levels of Transmission between Humans and Dogs

Schistosomiasis is a disease caused by parasitic worms known as schistosomes, which infect about 200 million people worldwide. In the Philippines, as in China, the species of schistosome (Schistosoma japonicum) which causes the disease infects not only humans, but also many other species of mammals. In China, bovines are thought to be particularly important for harboring and transmitting S. japonicum, whereas in the Philippines infections in bovines are relatively rare. However, dogs, rats and pigs are often infected with S. japonicum in the Philippines, although the extent to which infections in these animals may give rise to human infections is unclear. To help answer this question, we characterized the genetic variation of the parasite in Samar province of the Philippines, and found that S. japonicum samples from humans, dogs, rats and pigs were genetically very similar, with no significant genetic difference between samples from humans and dogs. This suggests that in the Philippines this parasite is frequently transmitted between different mammalian species, particularly between dogs and humans. Reducing levels of infections in dogs may therefore help to reduce infections in humans. The results also suggest high levels of transmission between geographic areas, thus regional co-ordination of treatment programs is recommended

Health Indicators of Native Hawaiian and Pacific Islanders in the United States

This study aimed to describe health indicators and behaviors of Native Hawaiian and Pacific Islander (NHPI) adults and to compare findings to previous reports on US NHPI and the US population. A sample of N = 100 (56 M, 44 F) NHPI adults aged 40–59 years completed an anonymous questionnaire addressing education and household income, tobacco use, physical activity, fruit and vegetable (F&V) consumption, cancer screening and health status. Objective measures of height and weight were taken to calculate body mass index (BMI). The study sample consisted of 49% current smokers and the majority was not meeting guidelines for physical activity (80%) or F&V consumption (99%). Cancer screening rates ranged from 0 to 57% and were higher among females. Mean BMI was 33.9 ± 7.5 kg/m2 and 95% were overweight or obese. While 36.7% were hypertensive, only 11.1% were taking prescribed medication. Compared to both the general US population and available data for US NHPI, study participants reported higher prevalence of obesity and chronic conditions (hypertension, high cholesterol, diabetes, and angina/CHD) and lower levels of physical activity, F&V consumption and cancer screening rates. Study findings contribute to the limited knowledge regarding health behaviors of US NHPI. Comparisons to US data increase evidence of NHPI health disparities, while comparisons to previous NHPI studies emphasize the magnitude of unhealthy lifestyle behaviors and subsequent adverse health conditions for this particular sample. Further improvements to community outreach and recruitment strategies could successfully encourage high-risk individuals to participate in health promotion and behavior intervention studies to improve NHPI health behaviors

The Synergistic Effect of Concomitant Schistosomiasis, Hookworm, and Trichuris Infections on Children's Anemia Burden

Polyparasitic infections have been recognized as the norm in many tropical developing countries, but the significance of this phenomenon for helminth-associated morbidities is largely unexplored. Earlier studies have suggested that multi-species, low-intensity parasitic infections were associated with higher odds of anemia among school-age children relative to their uninfected counterparts or those with one low-intensity infection. However, specific studies of the nature of interactions between helminth species in the mediation of helminth-associated morbidities are lacking. This study quantifies the extent to which polyparasitic infections have more than the sum of adverse effects associated with individual infections in the context of childhood anemia. This study found that the risk of anemia is amplified beyond the sum of risks for individual infections in children simultaneously exposed to 1) hookworm and schistosomiasis, and 2) hookworm and trichuris, and suggests that combined treatment for some geohelminth species and schistosomiasis could yield greater than additive benefits for the reduction of childhood anemia in helminth-endemic areas. However, more studies to understand the full range of interactions between parasitic species in their joint effects on helminth-associated morbidities will be necessary to better predict the impact of any future public health intervention

Transmission Dynamics of Schistosoma japonicum in the Lakes and Marshlands of China

Background: Schistosoma japonicum is a major public health concern in China, with over one million people infected and another 40 million living in areas at risk of infection. Unlike the disease caused by S. mansoni and S. haematobium, schistosomiasis japonica is a zoonosis, involving a number of different mammalian species as reservoir hosts. As a result of a number of published reports from China, it has long been considered that bovines, particularly water buffaloes, play a major role in human S. japonicum transmission there, and a drug-based intervention study (1998-2003) around the Poyang Lake in Jiangxi Province provided proof of concept that water buffaloes are, indeed, major reservoirs of human infection in this setting. Methods and Findings: In this study we incorporated recently obtained epidemiological information to model the steady-state S. japonicum transmission as well as the impact of the removal of S. japonicum transmission attributable to water buffaloes on human infection rates across six different endemic scenarios within three villages in the Dongting (Hunan) and Poyang (Jiangxi) lakes of southern China. Similar results were obtained for all scenarios. Steady-state S. japonicum infection rates remained constant and human prevalence and incidence were predicted to fall considerably over time. The model showed that the contribution of S. japonicum water buffalo transmission to human infection ranged from 39.1% to 99.1% and predicted that the removal of water buffalo transmission would reduce parasite reproductive rates below 1. This indicates that without the contribution of water buffaloes, S. japonicum transmission is interrupted and unsustainable. These scenarios are generalizable to other endemic villages in the lake and marshland areas of China where a similar cycle of snail infection and infection/reinfection of humans and bovines occurs. Conclusions: Along with previous epidemiological data, our findings strongly support water buffaloes as an important component of the transmission cycle that affects humans in the lake and marshlands region of China, a feature which appears to differ from the situation prevalent in the Philippines where their contribution is less pronounced. Our conclusions underscore the rationale for removal, replacement or treatment of water buffaloes, and for the development and deployment of a transmission blocking buffalo vaccine against S. japonicum for this setting to achieve the goal of transmission control. The Chinese Government has recently commenced a new integrated national strategy to improve on existing approaches to control schistosomiasis in the lake and marshlands region by reducing bovines and humans as a source of S. japonicum infection to Oncomelania snails

Transmission of Schistosoma japonicum in Marshland and Hilly Regions of China: Parasite Population Genetic and Sibship Structure

The transmission dynamics of Schistosoma japonicum remain poorly understood, as over forty species of mammals are suspected of serving as reservoir hosts. However, knowledge of the population genetic structure and of the full-sibship structuring of parasites at two larval stages will be useful in defining and tracking the transmission pattern between intermediate and definitive hosts. S. japonicum larvae were therefore collected in three marshland and three hilly villages in Anhui Province of China across three time points: April and September-October 2006, and April 2007, and then genotyped with six microsatellite markers. Results from the population genetic and sibling relationship analyses of the parasites across two larval stages demonstrated that, within the marshland, parasites from cattle showed higher genetic diversity than from other species; whereas within the hilly region, parasites from dogs and humans displayed higher genetic diversity than those from rodents. Both the extent of gene flow and the estimated proportion of full-sib relationships of parasites between two larval stages indicated that the cercariae identified within intermediate hosts in the marshlands mostly came from cattle, whereas in the hilly areas, they were varied between villages, coming primarily from rodents, dogs or humans. Such results suggest a different transmission process within the hilly region from within the marshlands. Moreover, this is the first time that the sibling relationship analysis was applied to the transmission dynamics for S. japonicum