Exploring the Potential Transmission Risk of Schistosomiasis Japonica in the Lower Reaches of the Yangtze River, China

Vector snails are important in the life cycle of schisosomiasis, the need to understand the ecologic factors that could enhance snails’ survival and trigger schistosomiasis transmission necessitated this study. Therefore, the potential risk of schistosomiasis transmission was explored in Zhangjiagang region, a non-endemic area in lower reaches of Yangtze River, eastern of China. The key indictors, including snail survival rate, spawn rate, hatching rate and gland development, were investigated through the designed experiments, routine snail and infectious source surveillance. The results showed that there was no significant difference in surviving rate, spawn rate, hatching rate and gland development between groups of simulated environments in laboratory, similar finding in field experiments, which suggested that snails stand a high possibility to survive in these non-endemic areas once they spread into these areas from other places. And no snails and infectious source were found either in the previous routine monitoring in the past decades and the snail surveillance we conducted from 2007 to 2013. Therefore, there is little risk in the study areas in the lower reaches of the Yangtze River. However, the sporadic and imported cases are still seen in a few areas adjacent to the endemic or transmission interrupted areas as the important infectious source, thus become a risk of schistosomisis transmission or re-emergence in these areas where the snail exists. Hence, maintaining routine monitoring and surveillance can be one of the effective and efficient ways to prevent the re-emergence of Schistosomiasis

A Molecular Investigation of Malaria Infections From High-Transmission Areas of Southern Togo Reveals Different Species of Plasmodium Parasites

Malaria particularly burdens people in poor and neglected settings across the tropics of Africa. Meanwhile, a large proportion of the Togo population have poor understanding of malaria epidemiology and parasites. This study carried out a molecular survey of malaria cases in southern Togo during 2017–2019. We estimated Plasmodium species infection rates and microscopic examination compliance with nested PCR results. Sensitivity and specificity analyses were performed in conjunction with predictive values. Also, phylogenetic characterization of species of malaria parasites was assessed. Plasmodium genus-specific nested PCR identified 565 positive cases including 536/611 (87.8%) confirmed cases from the microscopy-positive group and 29/199 (14.6%) diagnosed malaria cases from the microscopy-negative group. Our findings revealed a disease prevalence (69.8%) higher than that reported (25.5–55.1%) for the country. The diagnostic test had 94.9% sensitivity and 69.4% specificity, i.e., it missed 120 of the people who had malaria and about one-third of the people tested positive for the disease, which they did not have, respectively. In conjunction, the test showed 87.7% positive predictive value and 85.4% negative predictive value, which, from a clinical perspective, indicates the chance that a person with a positive diagnostic test truly has the disease and the probability that a person with a negative test does not have the disease, respectively. Further species-specific nested PCR followed by analysis of gene sequences confirmed species of malaria parasites and indicated infection rates for Plasmodium falciparum (Pf), 95.5% (540/565); P. ovale (Po), 0.5% (3/565); and P. malariae (Pm), 0.4% (2/565). In addition, 20 cases were coinfection cases of Pf-Po (15/565) and Pf-Pm (5/565). This study publicly reports, for the first time, a molecular survey of malaria cases in Togo and reveals the presence of other malaria parasites (Po and Pm) other than Pf. These findings might provide answers to some basic questions on the malaria scenario and, knowledge gained could help with intervention deployment for effective malaria control in Togo

Integrating ecological approaches to interrupt schistosomiasis transmission: opportunities and challenges

Abstract Background The development of agenda for global schistosomiasis elimination as a public health problem generates enthusiasms among global health communities, motivating great interests in both research and practice. Recent China-Africa schistosomiasis control initiatives, aiming to enhance collaboration on disease control in African countries, reflect in part that momentum. Yet there is a pressing need to know whether the Chinese experiences can be translated and applied in African settings. Main body China’s remarkable achievements in schistosomiasis control programme, associated experiences and lessons, have much to offer to those combating the disease. Central to the success of China’s control programmes is a strategy termed “integrated control” – integrating environmental approaches (e.g. improved sanitation, agricultural and hydrological development and management), which target different phases of the parasite transmission system, to chemical-based drug treatment and mollusciciding. Yet, despite significant measurable public health benefits, such integration is usually based on field experience and remains largely uncharacterized in an ecological context. This has limited our knowledge on relative contributions of varying components of the integrated control programme to the suppression of disease transmission, making it challenging to generalize the strategy elsewhere. In this opinion article, we have described and discussed these challenges, along with opportunities and research needs to move forward. Conclusions There is an urgent need to formalize an ecological framework for the integrated control programme that would allow research towards improved mechanistic understanding, quantification, and prediction of the control efforts

Whole-genome sequencing and analysis of Plasmodium falciparum isolates from China-Myanmar border area

Abstract Background China has made progress in malaria control and aims to eliminate malaria nationwide, but implementing effective interventions along the border regions remain a huge task. The Plasmodium falciparum cases imported from Southeast Asia has frequently reported especially in the China-Myanmar border (CMB) area. Though, information is scant on P. falciparum genetic variability in this area. Methods This study reported P. falciparum isolates genome sequence of six clinical isolates in the CMB area. Furthermore, we estimated the nucleotide diversity, Watterson’s estimator and Tajima’s D value for the whole genome mutation rate in slide window. Results Our data were aligned onto 96.05–98.61% of the reference 3D7 genome in high fold coverages. Principal component analysis result showed that P. falciparum clustered generally according to their geographic origin. A total of 91 genes were identified as positive selection with Ka/Ks ratio significantly higher than 1, and most of them were multigene families encoding variant surface antigens (VSAs) such as var, rif and stevor. The enrichment of the positive selection on VSA genes implied that the environment complexity subjected CMB’s P. falciparum to more pressure for survival. Conclusions Our research suggests that greater genetic diversity in CMB area and the positive selection signals in VSA genes, which allow P. falciparum to fit the host immune system well and aggravate the difficulty of treatment. Meanwhile, results obtained from this study will provide the fundamental basis for P. falciparum population genomic research in CMB area

Pattern analysis of schistosomiasis prevalence by exploring predictive modeling in Jiangling County, Hubei Province, P.R. China

Abstract Background The prevalence of schistosomiasis remains a key public health issue in China. Jiangling County in Hubei Province is a typical lake and marshland endemic area. The pattern analysis of schistosomiasis prevalence in Jiangling County is of significant importance for promoting schistosomiasis surveillance and control in the similar endemic areas. Methods The dataset was constructed based on the annual schistosomiasis surveillance as well the socio-economic data in Jiangling County covering the years from 2009 to 2013. A village clustering method modified from the K-mean algorithm was used to identify different types of endemic villages. For these identified village clusters, a matrix-based predictive model was developed by means of exploring the one-step backward temporal correlation inference algorithm aiming to estimate the predicative correlations of schistosomiasis prevalence among different years. Field sampling of faeces from domestic animals, as an indicator of potential schistosomiasis prevalence, was carried out and the results were used to validate the results of proposed models and methods. Results The prevalence of schistosomiasis in Jiangling County declined year by year. The total of 198 endemic villages in Jiangling County can be divided into four clusters with reference to the 5 years’ occurrences of schistosomiasis in human, cattle and snail populations. For each identified village cluster, a predictive matrix was generated to characterize the relationships of schistosomiasis prevalence with the historic infection level as well as their associated impact factors. Furthermore, the results of sampling faeces from the front field agreed with the results of the identified clusters of endemic villages. Conclusion The results of village clusters and the predictive matrix can be regard as the basis to conduct targeted measures for schistosomiasis surveillance and control. Furthermore, the proposed models and methods can be modified to investigate the schistosomiasis prevalence in other regions as well as be used for investigating other parasitic diseases

Differentiating snail intermediate hosts of Schistosoma spp. using molecular approaches: fundamental to successful integrated control mechanism in Africa

Abstract Background Snail intermediate hosts play active roles in the transmission of snail-borne trematode infections in Africa. A good knowledge of snail-borne diseases epidemiology particularly snail intermediate host populations would provide the necessary impetus to complementing existing control strategy. Main body This review highlights the importance of molecular approaches in differentiating snail hosts population structure and the need to provide adequate information on snail host populations by updating snail hosts genome database for Africa, in order to equip different stakeholders with adequate information on the ecology of snail intermediate hosts and their roles in the transmission of different diseases. Also, we identify the gaps and areas where there is need for urgent intervention to facilitate effective integrated control of schistosomiasis and other snail-borne trematode infections. Conclusions Prioritizing snail studies, especially snail differentiation using molecular tools will boost disease surveillance and also enhance efficient schistosomaisis control programme in Africa

Temporal clustering of acute cases infected with <i>S. japonicum</i> with moving window from 2005 to 2010 and 2012.

<p>Temporal clustering of acute cases infected with <i>S. japonicum</i> with moving window from 2005 to 2010 and 2012.</p

Number of acute schistosomiasis cases and outbreaks reported by provinces from 2005 to 2012.

<p>TC = Total number of acute cases; IC = Imported cases; OB = Outbreaks.</p><p>*cases from Ethiopia.</p

Schistosomiasis distribution in China in 2011.

<p>Schistosomiasis distribution in China in 2011.</p

Composition of acute schistosomiasis cases from 2005 to 2012.

<p>Composition of acute schistosomiasis cases from 2005 to 2012.</p