Nucleic acid detection in the diagnosis and prevention of schistosomiasis

Schistosomiasis is an important zoonotic parasitic disease that causes serious harms to humans and animals. Surveillance and diagnosis play key roles in schistosomiasis control, however, current techniques for surveillance and diagnosis of the disease have limitations. As genome data for parasites are increasing, novel techniques for detection incorporating nucleotide sequences are receiving widespread attention. These sensitive, specific, and rapid detection methods are particularly important in the diagnosis of low-grade and early infections, and may prove to have clinical significance. This paper reviews the progress of nucleic acid detection in the diagnosis and prevention of schistosomiasis, including such aspects as the selection of target genes, and development and application of nucleic acid detection methods. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40249-016-0116-y) contains supplementary material, which is available to authorized users

Prospects for Schistosomiasis Elimination

Current efforts to limit the ravages of schistosomiasis are pushing the world closer to eliminating a chronic infection that has been associated with human life in the tropics since time immemorial. This notwithstanding, the disease remains a scourge for large populations in sub-Saharan Africa, Latin America, and Southeast Asia, and the main part of this book is made up by papers dealing with its current distribution, discussing ways and means to establish and implement improved control approaches. While chemotherapy limits the symptoms caused by schistosomiasis, the number of infected people will not decrease until the parasite's life cycle is interrupted. To that end, some papers focus on the intermediate snail host, which is notoriously difficult to control, while others discuss human hygiene and sanitation. The latter approach not only prevents infection through avoiding people being infected from the snail, but more importantly, also stops people infecting the snail by leaving contagious feces and urine in nature. With morbidity reduced by chemotherapy, the immediate target now is the interruption of transmission to be achieved by new tools, such as the novel chemotherapies, improved diagnostics (for humans, animals, and snails), and vaccines discussed in several of the papers. As made clear in this book, a complex infection requires new tools as well as work on many fronts, above all; however, a clear idea is needed as to how to skillfully combine the tools available and sustain implemented control activities

Immune Events Associated with High Level Protection against Schistosoma japonicum Infection in Pigs Immunized with UV-Attenuated Cercariae

BACKGROUND: The vaccination of radiation-attenuated Schistosoma japonicum cercariae can induce effective protection in artiodactyl, but the immune events related to protective immunity are not fully understood. To provide a paradigm for a human recombinant antigen vaccine, we have undertaken a vaccination and challenge experiment in pigs, which was recognized as an appropriate animal model in this type of study because of their similarity to human in immunology, and investigated the relative immune events induced by the radiation-attenuated S. japonicum cercariae. METHODS AND FINDINGS: We found that pigs immunized once with 400 µw UV-irradiated cercariae exhibited 63.84% and 71.82% reductions in worm burden and hepatic eggs respectively. Protective immunity in vaccinated pigs was associated with high level productions of IgM, total IgG, IgG1 and IgG2; IgG2 was significantly increased in the acute infection. IFN-γ levels could be elicited by immunization. At week 6 post-infection, IFN-γ, IL-4 and IL-10 levels also showed a dramatic rise synchronously in vaccinated pigs. Moreover, the granzyme b, nk-lysin, ifnγ, il4 and il10 mRNA levels in early skin-draining lymph nodes of immunized pigs were higher than those in pigs with non-irradiated cercariae infection. In addition, cytotoxicity-related genes in the mesenteric lymph nodes were significantly upregulated in vaccinated pigs in the acute infection. CONCLUSION/SIGNIFICANCE: Our results demonstrated that IFN-γ and IgG2 antibody production, as well as genes related to cytotoxicity are associated with the high level protection induced by UV-irradiated Schistosoma japonicum vaccine. These findings indicated that optimal vaccination against S. japonicum required the induction of IFN-γ, IgG2 antibody related to Th1 responses and cytotoxicity effect

Studies on the Diagnosis of Schistosoma japonicum Infection Utilizing Real-time PCR and ELISA

岐阜大学(Gifu University)博士(獣医学)博士論文 (Doctoral dissertation)doctoral thesi

Heterobilharzia americana in Dogs: Characterizing Clinical Infection, Evaluating Diagnostic Test Performance, and Exploring Novel Methods of Diagnosis

Heterobilharzia americana is a waterborne trematode parasite (Family: Schistosomatidae) of dogs. More complete information regarding clinical, geographic, and diagnostic aspects of this parasite is needed to aid in more effective awareness and diagnosis. A total of 238 cases diagnosed through the Texas A&M Veterinary Medical Diagnostic Laboratory, Texas A&M Veterinary Medical Teaching Hospital, Texas A&M Diagnostic Parasitology Service, and Texas A&M Gastrointestinal Laboratory were reviewed. Cases were distributed primarily in the eastern region of Texas. Clinical signs were diarrhea (67%), weight loss (38%), anorexia/hyporexia (27%), vomiting (22%), hematochezia (20%), lethargy (17%), and polyuria/polydipsia (6%). H. americana was attributed to death in 20 of 39 necropsy cases. Trematode eggs were identified histologically in the small intestine (84%), liver (84%), large intestine (39%), pancreas (35%), lung (9%), lymph node (8%), and spleen (4%). A total of 69 dogs were enrolled in a diagnostic methods comparison study. Relative test sensitivities were 50% (29.1-70.9) for fecal saline sedimentation, 58.3% (36.6-77.9) for PCR of fresh feces, and 95.8% (78.9-99.9) for PCR of fecal sediment. PCR of fresh feces was no more sensitive than fecal saline sedimentation. Circulating anodic antigen was detected in the serum of 8 dogs using the Schistosoma mansoni point-of-care assay (POC-CAA). Circulating cathodic antigen was detected in urine of 7 dogs using the POC-CCA test. Next generation sequencing technology and the Galaxy-based RepeatExplorer computation pipeline were used to discover highly repetitive DNA sequences in the H. americana genome. A novel probe-based real-time PCR diagnostic assay targeting these highly repetitive sequences was developed. No DNA amplification was detected when testing DNA of common parasites indicating that the assay is highly specific. The real-time assay detected 9 samples as positive that were negative by conventional PCR targeting a segment of the 18S ribosomal DNA. Increased awareness of H. americana by veterinarians is crucial for a timely diagnosis. Promising methods to increase test sensitivity include sample concentration before DNA extraction, and using highly repetitive DNA targets in a real-time PCR assay. Circulating antigens were detected in some dogs; however, more sensitive test modalities should be developed in order to make circulating antigens accurate diagnostic targets

Quantitative Detection of Schistosoma japonicum Cercariae in Water by Real-Time PCR

In China alone, an estimated 30 million people are at risk of schistosomiasis, caused by the Schistosoma japonicum parasite. Disease has re-emerged in several regions that had previously attained transmission control, reinforcing the need for active surveillance. The environmental stage of the parasite is known to exhibit high spatial and temporal variability, and current detection techniques rely on a sentinel mouse method which has serious limitations in obtaining data in both time and space. Here we describe a real-time PCR assay to quantitatively detect S. japonicum cercariae in laboratory samples and in natural water that has been spiked with known numbers of S. japonicum. Multiple primers were designed and assessed, and the best performing set, along with a TaqMan probe, was used to quantify S. japonicum. The resulting assay was selective, with no amplification detected for Schistosoma mansoni, Schistosoma haematobium, avian schistosomes nor organisms present in non-endemic surface water samples. Repeated samples containing various concentrations of S. japonicum cercariae showed that the real-time PCR method had a strong linear correlation (R2 = 0.921) with light microscopy counts, and the detection limit was below the DNA equivalent of half of one cercaria. Various cercarial concentrations spiked in 1 liter of natural water followed by a filtration process produced positive detection from 93% of samples analyzed. The real-time PCR method performed well quantifying the relative concentrations of various spiked samples, although the absolute concentration estimates exhibited high variance across replicated samples. Overall, the method has the potential to be applied to environmental water samples to produce a rapid, reliable assay for cercarial location in endemic areas

Characterisation of the proteomic composition of Schistosoma haematobium extracellular vesicles: towards the development of vaccine and diagnostic candidate antigens

Gebeyaw Getnet Mekonnen characterised the proteomic composition of different populations of extracellular vesicles (EVs) from Schistosoma haematobium adult worms and assessed the vaccine and diagnostic efficacy of selected EV-membrane proteins. He found that S. haematobium EV tetraspanins are potential diagnostic candidates, which has resulted in a patent