Genetic manipulation of schistosomes

In contrast to the situations with model organisms and parasitic protozoa, progress with gene manipulation with schistosomes has been delayed by impediments that include our inability to maintain the life cycle in vitro, absence of immortalized cell lines, large genome sizes, unavailability of drug resistance markers and other difficulties. However, in the past few years, tangible progress has been reported towards development of tools for gene manipulation and transgenesis of schistosomes, and there is reason to believe that the field is on the verge of transformation into an era where genetic manipulation is routine. Recent reports dealing with approaches and tools to manipulate the genome and gene expression in schistosomes are reviewed here.     

A description of rodlet cells from the alimentary canal of Anguilla anguilla and their relationship with parasitic helminths

Rodlet cells in intestinal epithelia of infected and uninfected European eels Anguilla anguilla from brackish and fresh water were studied by light and electron microscopy. Deropristis inflata (Trematoda) was found in eels from brackish water, whereas eels from fresh water were infected with Acanthocephalus clavula (Acanthocephala). In a comparison between uninfected and infected eels from brackish water, a higher number of rodlet cells was recorded in the intestinal epithelia of infected fish. Evidence is presented that rodlet cells secrete their contents in a holocrine manner into the lumen of the eel intestine. The occurrence of organelles within the mature rodlet cell was rare. ? 1998 The Fisheries Society of the British Isles     

Purification and crystallization of a schistosomal glutathione S-Transferase

The 26-kDa glutathione S-transferase from Schistosoma japonica (Sj26), a potential antischistosomal vaccine antigen, has been crystallized in an unligated form. Sj26 was recombinantly produced in E. coli without using a glutathione affinity column to facilitate preparation of unligated enzyme. The recombinant protein contains all 218 residues of Sj26^1,2 and an additional 13 residues linked to the C-terminus. Crystals of recombinant Sj26 were obtained by the vapor diffusion method using ammonium sulfate as the precipitant at pH 5.6. The crystals belong to the hexagonal space group P6₃22 with unit cell dimensions a = b = 125.2 Å and c = 72.0 Å and contain one Sj26 monomer per asymmetric unit. A complete native diffraction data set has been obtained to 2.4 Å resolution. © 1995 Wiley-Liss, Inc.     

寄生蠕虫的群体遗传学研究

寄生蠕虫群体遗传学研究常用的遗传标记有等位酶、线粒体DNA、随机扩增多态性DNA或扩增性片段长度多态性和微卫星DNA等。应用这些遗传标记的研究表明,大多数寄生蠕虫群体遗传结构有不同水平的变异,这些变异的产生主要与寄生虫的生活史和群体生态、宿主的地理分布和环境等因素有关,并因此提出了有关遗传变异的一些假说。本文对寄生蠕虫群体遗传学的研究作一综述。 Abstract:Genetic markers including allozyme,mtDNA,RAPD/RFLP and micro DNA have been used in the research of helminth population genetics.Available data on helminth genetic variability have shown that most helminth populations exhibit different levels of genetic variation resulting mainly from the pattern of life cycle,geographical distribution and parasite-host interaction,and several hypotheses have been proposed to explain the genetic variation.     

Inhibition of p-450 aromatase prevents feminisation and induces protection during cysticercosis

Cysticercotic male mice undergo an impressive feminisation process, characterised by 200 times increased serum 17beta-estradiol levels while testosterone and dihydrotestosterone are 90% reduced, which results in elevated parasite burden. Administration of Fadrozole (an aromatase inhibitor) in male and female mice suppressed the production of 17beta-estradiol, accompanied with a 70% reduction in parasite burden. This protective effect was associated in male mice with a recovery of the specific cellular immune response. Interleukin-6 (IL-6) serum levels, and its production by splenocytes, was augmented by 80%, together with a 10-fold increase in its expression in testes of infected male mice. Fadrozole treatment returned these levels to baseline values. Aromatase expression in the testes of infected male mice was not affected by Fadrozole. These results suggest that aromatase and IL-6 are key molecules in the production of the feminisation undergone by infected male mice and to Fadrozole treatment as a possible new therapeutic approach to cysticercosis.     

鲻鱼(Mugil cephalus)寄生蠕虫群落生态研究

从1017尾鲻鱼（Mugil cephalus）肠道内获得寄生蠕虫9种,均为常见种类,即复殖吸虫（Digeneans）8种,棘头虫（Aacnthodephala）1种,总感染率为24.0％,平均感染强度8.73,种群平均密度2.10,其中惠东拟囊腔吸虫（Saccocoe-lioides huidongensis）的感染率、感染强度和平均密度最大。鲻鱼寄生蠕虫群落多样性指数为20193,群落均匀度指标为0.6370。鲻鱼感染寄生蠕虫种数在1－3种之间,优势种1种,为惠东拟腔吸虫;次优势种3种,分别为鲻长尾吸虫（E－longinus mugilus）、单睾椭囊吸虫（Elliptobursa singlorchis）和圆颚针鱼新棘吻虫（Neoechinorhynchus tylosuri）;非优势种5种,分别为楔形单脏吸虫（Haplosplanchnus cuneatus）、长形单脏吸虫（Haplosplanchnus elongatus）、双睾原单脏吸虫（Pro-haplosplanchus diorchis）、粤东纵睾吸虫（Tandemorchis yuedongensis）和浦里单脏吸虫（Haplosplanchnus purii）。略多于 寄生蠕虫复合群落和组分群落在一年四季中均由9种蠕虫组成,其感染率、平均感染强度和平均密度变化各有所不同,即从夏季开始,鲻鱼寄生蠕虫总感染率和各组分群落的平均密度则逐渐增高,冬季碹以一个高峰,随后逐渐下降;鲻鱼寄生蠕虫复合群落的平均密度从冬季开始逐渐下降,至秋季为最低;而圆颚针鱼析棘吻虫的感染率的四季变化与8种吸虫的变化趋势差异较大,即从春末开始增大,夏季达到最大值,随后维持在一个较高水平上,至春初则有所下降。9种寄生蠕虫的种间协调关系经卡方值测定,呈无明显协调关系。各种寄生蠕虫的种群分布均为聚集分布。     

Integrated Schistosomiasis and Soil-Transmitted Helminthiasis Control over Five Years on Kome Island,Tanzania

Integrated control strategies are important for sustainable control of schistosomiasis and soil-transmitted helminthiasis, despite their challenges for their effective implementation. With the support of Good Neighbors International in collaboration with National Institute of Medical Research, Mwanza, Tanzania, integrated control applying mass drug administration (MDA), health education using PHAST, and improved safe water supply has been implemented on Kome Island over 5 years for controlling schistosomiasis and soil-transmitted helminths (STHs). Baseline surveys for schistosomiasis and STHs was conducted before implementation of any integrated control strategies, followed by 4 cross-sectional follow-up surveys on randomly selected samples of schoolchildren and adults in 10 primary schools and 8 villages, respectively, on Kome islands. Those follow-up surveys were conducted for impact evaluation after introduction of control strategies interventions in the study area. Five rounds of MDA have been implemented from 2009 along with PHAST and improved water supply with pumped wells as other control strategies for complementing MDA. A remarkable steady decline of schistosomiasis and STHs was observed from 2009 to 2012 with significant trends in their prevalence decline, and thereafter infection rate has remained at a low sustainable control. By the third follow-up survey in 2012, Schistosoma mansoni infection prevalence was reduced by 90.5% and hookworm by 93.3% among schoolchildren while in adults the corresponding reduction was 83.2% and 56.9%, respectively. Integrated control strategies have successfully reduced S. mansoni and STH infection status to a lower level. This study further suggests that monitoring and evaluation is a crucial component of any large-scale STH and schistosomiasis intervention.     

Neglected tropical diseases in Central America and Panama: Review of their prevalence,populations at risk and impact on regional development

A review of the literature since 2009 reveals a staggering health and economic burden resulting from neglected tropical diseases in Panama and the six countries of Central America (referred to collectively here as ‘Central America’). Particularly at risk are the 10.2 million people in the region who live on less than $2 per day, mostly in Guatemala, Honduras, Nicaragua and El Salvador. Indigenous populations are especially vulnerable to neglected tropical diseases. Currently, more than 8 million Central American children require mass drug treatments annually (or more frequently) for their intestinal helminth infections, while vector-borne diseases are widespread. Among the vector-borne parasitic infections, almost 40% of the population is at risk for malaria (mostly Plasmodium vivax infection), more than 800,000 people live with Chagas disease, and up to 39,000 people have cutaneous leishmaniasis. In contrast, an important recent success story is the elimination of onchocerciasis from Central America. Dengue is the leading arbovirus infection with 4–5 million people affected annually and hantavirus is an important rodent-borne viral neglected tropical disease. The leading bacterial neglected tropical diseases include leptospirosis and trachoma, for which there are no disease burden estimates. Overall there is an extreme dearth of epidemiological data on neglected tropical diseases based on active surveillance as well as estimates of their economic impact. Limited information to date, however, suggests that neglected tropical diseases are a major hindrance to the region’s economic development, in both the most impoverished Central American countries listed above, as well as for Panama and Costa Rica where a substantial (but largely hidden) minority of people live in extreme poverty.     

可可西里藏羚羊、野牦牛、藏野驴和藏原羚冬季蠕虫卵粪检研究初报

2004年12月25日~2005年1月5日,在可可西里地区收集到藏羚羊、野牦牛、藏野驴和藏原羚的新鲜粪便各36、16、13和20份带回实验室,利用漂浮法、沉淀法对其在冬季的寄生蠕虫卵进行检查。结果显示:藏羚羊、藏原羚粪便中均存在有细颈属线虫、马歇尔属线虫和莫尼茨属绦虫虫卵,藏羚羊的感染率在19.4%~94.4%之间,感染强度EPG分别为5.58、5.11和2.86;藏原羚感染率为15%~65%,感染强度EPG各自为11.1、2.45和12.65。野牦牛粪样有古柏属和毛圆属线虫卵,感染率在75%~87.5%之间,感染强度EPG为9.06和5.93;藏野驴粪样有裸头属绦虫卵和园形科线虫卵,感染率在31%~100%之间,感染强度EPG分别为3.77和104。粪检表明:冬季藏羚羊、野牦牛、藏野驴和藏原羚的蠕虫感染率高、感染种类少和感染强度低,动物处于带虫免疫状态。