Prevalence and distribution of soil-transmitted helminth infections in Nigerian children:a systematic review and meta-analysis

Background:Soil transmitted helminth(STH)infections still remain a notable health problem in resource-limited countries due to difficulties in the implementation of control measures.In Nigeria for instance,despite several community-based and provincial reports,national data on prevalence,burdens and risk zones(RZs)for STH infections are lacking.Methods:The present study employed the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)to determine the prevalence,distribution and RZs for STH infections among Nigerian children through a meta-analysis of data published between 1980 and 2015.Pooled prevalence estimate(PPE)was determined by the random-effects model while heterogeneity was evaluated using the Cochran’s Q-test.Results:A total of 18901 of the 34518 Nigerian children aged 0-17 years examined across 19 Nigerian states during the period under review were infected with one or more species of STHs.The overall PPE for STH infections was 54.8%(95%CI:54.2-55.3).PPEs for sub-groups ranged between 13.2%(95%CI:11.5-15.1)and 80.9%(95%CI:80.0-81.7).Highest PPEs for STH infections were observed among children within community settings(59.0%,95%CI:57.7-60.4)and school-aged children(54.9%,95%CI:54.3-55.5).Ascaris lumbricoides was the most prevalent species(44.6%,95%CI:44.0-45.2).Over 36%(15/41)of the studies were published from south-western Nigeria.South-western region was the only high risk zone(HRZ)for STH infections while the rest of the regions were low risk zones(LRZs).Conclusions:STH infections involving Ascaris lumbricoides,Strongyloides stercoralis,Trichuris trichiura and hookworms are highly prevalent across Nigeria.Strategic use of anthelmintics,health education and adequate sanitation,taking into account this epidemiologic information will help in the control of these infections in Nigeria.

Distinct clinical characteristics and helminth co-infections in adult tuberculosis patients from urban compared to rural Tanzania

Background:Differences in rural and urban settings could account for distinct characteristics in the epidemiology of tuberculosis(TB).We comparatively studied epidemiological features of TB and helminth co-infections in adult patients from rural and urban settings of Tanzania.Methods:Adult patients(≥18 years)with microbiologically confirmed pulmonary TB were consecutively enrolled into two cohorts in Dar es Salaam,with~4.4 million inhabitants(urban),and Ifakara in the sparsely populated Kilombero District with~400000 inhabitants(rural).Clinical data were obtained at recruitment.Stool and urine samples were subjected to diagnose helminthiases using Kato-Katz,Baermann,urine filtration,and circulating cathodic antigen tests.Differences between groups were assessed byχ2,Fisher’s exact,and Wilcoxon rank sum tests.Logistic regression models were used to determine associations.Results:Between August 2015 and February 2017,668 patients were enrolled,460(68.9%)at the urban and 208(31.1%)at the rural site.Median patient age was 35 years(interquartile range[IQR]:27-41.5 years),and 454(68%)were males.Patients from the rural setting were older(median age 37 years vs.34 years,P=0.003),had a lower median body mass index(17.5 kg/m2 vs.18.5 kg/m2,P<0.001),a higher proportion of recurrent TB cases(9%vs.1%,P<0.001),and in HIV/TB co-infected patients a lower median CD4 cell counts(147 cells/μl vs.249 cells/μl,P=0.02)compared to those from urban Tanzania.There was no significant difference in frequencies of HIV infection,diabetes mellitus,and haemoglobin concentration levels between the two settings.The overall prevalence of helminth co-infections was 22.9%(95%confidence interval[CI]:20.4-27.0%).The significantly higher prevalence of helminth infections at the urban site(25.7%vs.17.3%,P=0.018)was predominantly driven by Strongyloides stercoralis(17.0%vs.4.8%,P<0.001)and Schistosoma mansoni infection(4.1%vs.16.4%,P<0.001).Recurrent TB was associated with living in a rural setting(adjusted odds ratio[aOR]:3.97,95%CI:1.16-13.67)and increasing age(aOR:1.06,95%CI:1.02-1.10).Conclusions:Clinical characteristics and helminth co-infections pattern differ in TB patients in urban and rural Tanzania.The differences underline the need for setting-specific,tailored public health interventions to improve clinical management of TB and comorbidities.

The landscape epidemiology of echinococcoses

Echinococcoses are parasitic diseases of major public health importance globally.Human infection results in chronic disease with poor prognosis and serious medical,social and economic consequences for vulnerable populations.According to recent estimates,the geographical distribution of Echinococcus spp.infections is expanding and becoming an emerging and re-emerging problem in several regions of the world.Echinococcosis endemicity is geographically heterogeneous and over time it may be affected by global environmental change.Therefore,landscape epidemiology offers a unique opportunity to quantify and predict the ecological risk of infection at multiple spatial and temporal scales.Here,we review the most relevant environmental sources of spatial variation in human echinococcosis risk,and describe the potential applications of landscape epidemiological studies to characterise the current patterns of parasite transmission across natural and human-altered landscapes.We advocate future work promoting the use of this approach as a support tool for decision-making that facilitates the design,implementation and monitoring of spatially targeted interventions to reduce the burden of human echinococcoses in disease-endemic areas.

The roles of anurans in antagonistic networks are explained by life-habit and body-size

Interactions among living beings are the structuring basis of ecosystems,and studies of networks allow us to identify the patterns and consistency of such interactions.Antagonistic networks reflect the energy flow of communities,and identifying network structure and the biological aspects that influence its stability is crucial to understanding ecosystem functioning.We used antagonistic anuran interactions-predator-prey and host-parasite-to assess structural patterns and to identify the key anuran species structuring these networks.We tested whether anuran body-size and life-habit are related to their roles in these networks.We collected individuals of 9 species of anurans from an area of the Atlantic Forest in Brazil and identified their prey and helminth parasites.We used network(modularity,specialization,and nestedness)and centrality metrics(degree,closeness,and betweenness)to identify the role of anuran species in both networks.We then evaluated whether anuran body-size or life-habit were related to anuran centrality using generalized linear mixed models.The networks formed specialized interactions in compartments composed by key species from different habits.In our networks,anurans with rheophilic and cryptozoic habit are central in predator-prey networks,and those with larger body size and arboreal and cryptozoic habit in the host-parasite network.This study represents a step towards a better understanding of the influential factors that affect the structure of anuran antagonist networks,as well as to recognize the functioning roles of anuran species.