水牛感染血吸虫后病原消亡时间与防制对策的关系

目的 观察水牛感染血吸虫后排卵量和毛蚴出孵规律及其消失时间。 方法 选择购自血吸虫病非流行区8～ 10月龄水牛 9头 ,每头水牛感染血吸虫尾蚴 2 0 0 0条。从感染后第 5 0d开始定期收集粪便作定量检查血吸虫卵和毛蚴 ,连续观察 3 2个月。 结果 在感染血吸虫后第 5 0d 9头水牛均在粪便中发现血吸虫卵和毛蚴 ,平均EPG和MPG分别为 4.65± 2 .0 8和 4.3 6± 2 .19;感染后第 60d分别达 41.0 5± 2 .0 9和 2 5 .97± 2 .45 ,显著高于第 5 0d。感染后第 80d ,MPG为最高 41.73± 3 .2 9,感染后第 90d ,EPG达最高 5 5 .0 4± 1.44。以后随着观察时间的延长 ,EPG和MPG逐渐降低 ,至 3 3 0d全部为阴性。感染后第 5 0d毛蚴孵出率最高 94.45± 6.412 % ,第 60d降为 65 .89± 19.0 1% ,第 80d有所回升85 .76± 10 .5 0 % ,以后逐渐降低 ,至 3 3 0d全部为 0。感染后 1年 ,粪便中未再检出血吸虫卵。肝、脾和肠组织中的虫卵不能孵出毛蚴 ,但沉积在组织中的血吸虫卵仍可造成该组织损害。 结论 1岁以内的水牛感染血吸虫后 1年无需治疗虫体均可消亡 ,粪卵排出消失 ,但在肝脾组织中的血吸虫卵沉着所致病变仍存在。

口服蒿甲醚控制重疫区血吸虫病及预防急性感染

目的 观察口服蒿甲醚控制日本血吸虫病重疫区人群感染及预防急性感染的效果。方法 在鄱阳湖区血吸虫病易感季节（5～10月）对重疫区村居民采用15d间隔口服蒿甲醚预防感染。同时设对照组，口服安慰剂。结果 感染季节结束后，实验组人群粪检阳性率为0．83％，无急性感染发生；对照组粪检阳性率为15．01％，发生3例急性感染。结论 每15天间隔口服蒿甲醚1次，对重疫区人群有良好的保护作用，保护率为94．47％，有利于控制人群感染；对防止急性感染也有明显效果。

Optimisation of the DNA dipstick as a rapid extraction method for Schistosoma japonicum in infected mice samples and spiked human clinical samples

BackgroundSchistosomiasis remains a public health issue and the need for accurate and affordable diagnostics is crucial in the elimination of the disease. While molecular diagnostics are highly effective, they are expensive, with the main costs been associated with DNA extraction. The DNA dipstick is a rapid, affordable and simple purification method that allows DNA to be extracted from diagnostic samples within 30 s. We aimed to optimise the DNA dipstick method for samples from mice and egg-spiked human samples.MethodsUrine, blood and faeces were collected from mice exposed to Schistosoma japonicum infection at weekly intervals from Day 0 to Day 42. Urine and faecal samples were also collected from volunteer, uninfected humans and spiked with S. japonicum eggs. All samples were subject to several optimisation procedures and DNA extracted with the DNA dipstick. Amplification of the target DNA was carried out using LAMP and visualised using agarose gel electrophoresis and flocculation.ResultsThe DNA dipstick successfully identified S. japonicum from infected mice and human clinical samples spiked with cracked eggs or genomic DNA from S. japonicum. Amplification was observed from week 4 post infection in infected mice. For human samples, amplification was observed in sieved faecal samples, filtered urine samples heated at 95 ℃ for 30 min, and sera samples heated at 95℃ for 30 min.ConclusionsThe DNA dipstick combined with LAMP has huge potential in providing cost-effective, simple and accurate detection of schistosomiasis infection in endemic regions. This will allow for rapid treatment, tracking outbreaks—such as occur after typhoons, leading to better health outcomes and contributing to control and eventual elimination of schistosomiasis.

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.

Real-time PCR diagnosis of Schistosoma japonicum in low transmission areas of China

Background:Schistosomiasis in the People’s Republic of China(PRC)can be traced back to antiquity.In the past 60 years,the Chinese government has made great efforts to control this persistent disease with elimination slated by 2020 through the implementation of a comprehensive control strategy.This strategy aims to reduce the role of bovines and humans as sources of infection as a pre-requisite for elimination through transmission interruption.The goal of elimination will be achievable only by the implementation of a sustainable surveillance and control system,with sensitive diagnosis a key feature so that the true disease burden is not underestimated.Currently used diagnostics lack the necessary sensitivity to accurately determine the prevalence of Schistosoma japonicum infection in areas with low infection intensities.It is of critical importance to find and treat people and to identify animals with low-level infections if the National Control Programme for China is to achieve schistosomiasis elimination.Methods:We evaluated a real-time polymerase chain reaction(qPCR)assay using 633 human stool samples collected from five villages in Hunan,Anhui,Hubei,and Jiangxi provinces,and 182 bovine(70 cattle and 112 buffalo)stool samples obtained from four villages in Hunan,Anhui,and Jiangxi provinces in the PRC.All stool samples were subjected to the miracidium hatching test(MHT,a diagnostic procedure used in the National Schistosomiasis Control Programme)and the qPCR assay.Samples positive by MHT were subjected to either the Kato-Katz technique for humans,or the formalin-ethyl acetate sedimentation-digestion(FEA-SD)procedure for bovines,to determine infection intensities.Results:The qPCR assay exhibited a high level of sensitivity in the detection of S.japonicum infections.With both the human and bovine samples,a significantly higher prevalence was determined using the qPCR assay(11.06%humans,24.73%bovines)than with the MHT(0.93%humans,7.69%bovines).The animal contamination index(calculated using data obtained with the qPCR technique)for all positive bovines was 27618000 eggs per day,indicating a considerable amount of environmental egg contamination that would be underestimated using less sensitive diagnostic procedures.Conclusions:The qPCR assay we have evaluated will be applicable as a future field diagnostic and surveillance tool in low-transmission zones where schistosomiasis elimination is targeted and for monitoring post-intervention areas to verify that elimination has been maintained.

Estimating the prevalence of Echinococcus in domestic dogs in highly endemic for echinococcosis

Background:Cystic echinococcosis(CE)and alveolar echinococcosis(AE)are highly endemic in Xiji County of Ningxia Hui Autonomous Region(NHAR)in China where the control campaign based on dog de-worming with praziquantel has been undertaken over preceding decades.This study is to determine the current prevalence of Echinococcus granulosus and E.multilocularis in domestic dogs and monitor the echinococcosis transmission dynamics.Methods:Study villages were selected using landscape patterns(Geographic Information System,GIS)for Echinococcus transmission“hot spots”,combined with hospital records identifying risk areas for AE and CE.A survey of 750 domestic dogs,including copro-sampling and owner questionnaires,from 25 selected villages,was undertaken in 2012.A copro-multiplex PCR assay was used for the specific diagnosis of E.granulosus and E.multilocularis in the dogs.Data analysis,using IBM SPSS Statistics,was undertaken,to compare the prevalence of the two Echinococcus spp.in dogs between four geographical areas of Xiji by theχ^(2)test.Univariate analysis of the combinations of outcomes from the questionnaire and copro-PCR assay data was carried out to determine the significant risk factors for dog infection.Results:The highest de-worming rate of 84.0%was found in the northwest area of Xiji County,and significant differences(P<0.05)in the de-worming rates among dogs from the four geographical areas of Xiji were detected.The highest prevalence(19.7%,59/300)of E.multilocularis occurred in northwest Xiji,though the highest prevalence(18.1%,38/210)of E.granulosus occurred in southwest Xiji.There was no significant difference(P>0.05)in the prevalence of E.granulosus in dogs from the northwest,southwest,northeast,and southeast of Xiji,but there were significant differences(P<0.05)between dogs infected with E.multilocularis from the four areas.None of the other independent variables was statistically significant.Conclusions:The results from this study indicate a high prevalence of both E.granulosus and E.muiltilocularis in dogs in Xiji County,NHAR.Transmission of E.multilocularis was more impacted by geographical risk-factors in Xiji County than that of E.granulosus.Dogs have the potential to maintain the transmission of both species of Echinococcus within local Xiji communities,and the current praziquantel dosing of dogs appears to be ineffective or poorly implemented in this area.

The control of soil-transmitted helminthiases in the Philippines: the story continues

Background:Soil-transmitted helminth(STH)infections have long been an important public health concern in the Philippines.In this review,we describe the current status of STH infections there and highlight the control efforts undertaken to reduce STH burden.Main text:A nationwide STH mass drug administration(MDA)programme was started in 2006 but the overall STH prevalence remains stubbornly high across the Philippines,rangi ng from 24.9%to 97.4%.

Co-parasitism of intestinal protozoa and Schistosoma japonicum in a rural community in the Philippines

Background:Co-parasitism is a frequent occurrence in impoverished communities in the tropics resulting in a considerable disease burden.While there are extensive reports of intestinal helminthiases,including schistosomiasis japonica,the occurrence and extent of diseases caused by intestinal protozoa(IP)have yet to be investigated in depth in the Philippines.We present a detailed analysis of polyparasitism in a rural community of Northern Samar,focusing on co-infections of IP with Schistosoma japonicum.Methods:A descriptive cross sectional study was carried out in 2015 across 18 barangays(villages)endemic for S.japonicum in Northern Samar,the Philippines to assess the burden of human schistosomiasis and IP infections.Faecal samples collected from 412 participants from the 18 barangays were included in the final molecular analysis.A multiplex quantitative PCR assay was developed and used for the detection of Blastocystis spp.,Entamoeba histolytica,Cryptosporidium spp.and Giardia duodenalis in stool samples.The findings were combined with previous results of droplet digital PCR diagnosis of individuals from the same 18 barangays infected with S.japonicum determined using the same stool samples for analysis.Results:Mean age of the study participants was 40.3 years(95%CI:38.8-41.8)with 53%(n=218)being males.Prevalence of S.japonicum(74.5%)and Blastocystis spp.(58.7%)was significantly higher compared to other infections,with E.histolytica having the lowest prevalence(12.1%).A majority of individuals were infected with more than one parasite with two infections being most common(n=175,42.5%).The prevalence of individuals with two parasites was significantly higher than all others with 27.9%(n=115)subjects harbouring a single parasite species.Of individuals with two infections,S.japonicum and Blastocystis spp.were the most common combination(n=110,62.9%).Examining age within the population,58.5%(n=38)of school-aged children and 60.1%(n=14)of women of child bearing age harboured at least two parasite species.Conclusions:The study revealed that polyparasitism with IP infections and schistosomiasis japonica is highly prevalent in individuals in Northern Samar which likely contributes to the significant public health and socio-economic burden suffered by this population.More generally,the findings are of relevance when considering implementation of integrated control strategies for intestinal parasites.

Performance of the point-of-care circulating cathodic antigen test in the diagnosis of schistosomiasis japonica in a human cohort from Northern Samar, the Philippines

Background:Zoonotic schistosomiasis,caused by Schistosoma japonicum,remains a major public health problem in the Philippines.This study aimed to evaluate the commercially available rapid diagnostic point-of-care circulating cathodic antigen(POC-CCA)test in detecting individuals infected with S.japonicum in a human cohort from an endemic area for schistosomiasis japonica in the Philippines.Methods:Clinical samples were collectedin 18 barangays endemic for S.japonicum infection in Laoang and Palapag municipalities,Northern Samar,the Philippines,in 2015.The presence of CCA in flter-concentrated urine samples(n=412)was evaluated using the commercial kits and the results were converted to images,which were further analyzed by ImageJ software to calculate R values.The diagnostic performance of the immunochromatographic POCCCA test was compared using the Kato-Katz(KK)procedure,in-house enzyme-linked immunosorbent assays(ELISAs)and droplet digital(dd)PCR assays as reference.Results:The POC-CCA test was able to detect S.japonicum-infected individuals in the cohort with an eggs per gram of faeces(EPG)more than or equal to 10 with sensitivity/specifcity values of 63.3%/93.3%.However,the assay showed an inability to diagnose schistosomiasis japonica infections in all cohort KK-positive individuals,of which the majority had an extremely low egg burden(EPG:1–9).The prevalence of S.japonicum infection in the total cohort determined by the POC-CCA test was 12.4%,only half of that determined by the KK method(26.2%).When compared with the ELISAs and ddPCR assays as a reference,the POC-CCA assay was further shown to be a test with low sensitivity.Nevertheless,the assay exhibited signifcant positive correlations with egg burden determined by the KK technique and the target gene copy number index values determined by the ddPCR assays within the entire cohort.Conclusions:By using in silico image analysis,the POC-CCA cassette test could be converted to a quantitative assay to avoid reader-variability.Because of its low sensitivity,the commercially available POC-CCA assay had limited potential for determining the status of a S.japonicum infection in the target cohort.The assay should be applied with caution in populations where schistosome parasites(especially S.japonicum)are present at low infection intensity.

Health-education to prevent COVID-19 in schoolchildren: a call to action

Background:There is currently considerable international debate around school closures/openings and the role of children in the transmission of coronavirus disease 2019(COVID-19).Whilst evidence suggests that children are not impacted by COVID-19 as severely as adults,little is still known about their transmission potential,and with a lot of asymptomatic cases they may be silent transmitters(i.e.infectious without showing clinical signs of disease),albeit at a lower level than adults.In relation to this,it is somewhat concerning that in many countries children are cared for,or are often in close contact with,older individuals such as grandparents—the age group most at risk of acquiring serious respiratory complications resulting in death.Main text:We emphasise that in the absence of a vaccine or an effective therapeutic drug,preventive measures such as good hygiene practices—hand washing,cough etiquette,disinfection of surfaces and social distancing represent the major(in fact only)weapons that we have against COVID-19.Accordingly,we stress that there is a pressing need to develop specific COVID-19 prevention messages for schoolchildren.Conclusion:An entertainment education intervention for schoolchildren systematically implemented in schools would be highly effective and fill this need.With such measures in place there would be greater confidence around the opening of schools.