The soluble worm antigens-specific antibodies used as biomarkers of Schistosoma japonicum in a low prevalence and intensity endemic area of Hubei, China

Evaluation of isotype-based serology for diagnosis of Schistosoma mansoni infection in individuals living in endemic areas with low parasite burden

Intestinal schistosomiasis is a chronic and debilitating disease that affects public health systems worldwide. Control interventions to reduce morbidity primarily involve the diagnosis and treatment of infected individuals. However, the recommended Kato-Katz (KK) parasitological method shows low sensitivity in individuals with low parasite loads and is not useful for monitoring elimination of parasite transmission at later stages. In the current study, we evaluated the accuracy of serum reactivity levels of different immunoglobulin isotypes in an enzyme-linked immunosorbent assay (ELISA), utilizing Schistosoma mansoni crude extracts, with the aim to improve the diagnosis of infected individuals with low parasite loads. The serum reactivity of IgM and IgG subclass antibodies (IgG1, IgG3, and IgG4) against soluble adult worm and egg antigen preparations was evaluated in residents from a schistosomiasis-endemic area in northern Minas Gerais, Brazil. The parasitological status of the study population was determined through fecal examination with multiple parasitological tests to create a consolidated reference standard (CRS) plus a fecal DNA detection test (q-PCR). Twelve months after praziquantel treatment, a second serum sample was obtained from the population for reexamination. A two-graph receiver operating characteristic curve (TG-ROC) analysis was performed using the serum reactivity of non-infected endemic controls and egg-positive individuals, and the cut-off value was established based on the intersection point of the sensibility and specificity curves in TG-ROC analyses. The diagnostic accuracy of each serological test was evaluated in relation to the parasitological CRS and to the combination of CRS plus qPCR results. The data revealed that serum reactivity of IgM and IgG3 against S. mansoni antigens did not allow identification of infected individuals from the endemic area. In contrast, serum IgG1 and IgG4-reactivity against schistosome antigens could distinguish between infected and non-infected individuals, with AUC values ranging between 0.728-0.925. The reactivity of IgG4 anti-soluble egg antigen - SEA (sensitivity 79 %, specificity 69 %, kappa = 0.49) had the best diagnostic accuracy, showing positive reactivity in more than 75 % of the infected individuals who eliminated less than 12 eggs per gram of feces. Moreover, serum IgG4 reactivity against SEA and against soluble worm antigen preparation (SWAP) was significantly reduced in the serum of infected individuals after 12 months of confirmed parasitological cure and in the absence of re-infection. These results reinforce that the described IgG4 anti-SEA ELISA assay is a sensitive alternative for the diagnosis of active intestinal schistosomiasis in individuals from endemic areas, including in those with a very low parasite load.

Emerging biomedical tools for biomarkers detection and diagnostics in schistosomiasis

Schistosomiasis is a neglected disease that strikes many people from tropical and subtropical countries where there are not satisfactory sanitation and wide access to clean water. Schistosoma spp., the causative agents of schistosomiasis, exhibit a quite complex life cycle that involves two hosts (humans and snails, respectively, the definitive and the intermediate), and five evolutive forms: cercariae (human infective form), schistosomula, adult worms, eggs, and miracidia. The techniques to diagnose schistosomiasis still have various limitations, mainly regarding low-intensity infections. Although various mechanisms associated with schistosomiasis have already been evidenced, there is still a need to fulfill the comprehension of this disease, especially to prospect for novel biomarkers to improve its diagnosis. Developing methods with more sensitivity and portability to detect the infection is valuable to reach schistosomiasis control. In this context, this review has gathered information not only on schistosomiasis biomarkers but also on emerging optical and electrochemical tools proposed in selected studies from about the last ten years. Aspects of the assays regarding the sensibility, specificity, and time needed for detecting diverse biomarkers are described. We hope this review can guide future developments in the field of schistosomiasis, contributing to improving its diagnosis and eradication.

Helminthiases in the People's Republic of China: Status and prospects

Helminth infections, many of them listed as neglected tropical diseases by the World Health Organization, remain a public health issue in many parts of the world. The People's Republic of China (P.R. China) stands out due to impressive progress in the control and local elimination of helminth infections. An important contextual factor is P.R. China's sustained social and economic development that allowed implementation of health-related poverty alleviation, improving water, sanitation and hygiene, enhancing information, education and communication, coupled with major engineering and infrastructure development and intersectoral collaboration. Nonetheless, food-borne trematodiases, soil-transmitted helminthiases, echinococcosis, cysticercosis/taeniasis and schistosomiasis still exert a considerable burden in P.R. China, even though the numbers of infected people have decreased substantially since the new millennium. This special issue of Acta Tropica provides a comprehensive update of the current knowledge of the main helminth infections in P.R. China, summarises progress in research and discusses future prospects for gaining and sustaining control towards the final goal of breaking transmission and hence, eliminating helminthiases. It consists of 34 articles with a wide coverage that can be grouped into six domains: (i) epidemiological assessment and disease burden estimates; (ii) diagnostics and antigen characterisation; (iii) drug and vaccine development; (iv) host-parasite interactions and snail genetics; (v) surveillance and public health response; and (vi) capacity building and international cooperation. The control and elimination of helminthiases not only furthers the health and wellbeing of the Chinese people, but also provides innovative approaches, tools and strategies, which can be adopted and applied in other countries and regions of the world where helminthiases still prevail.