Taeniasis and cysticercosis in Asia and the Pacific: present state of knowledge and perspectives

Several topics on taeniasis and cysticercosis in Asia and the Pacific are overviewed. In Asia and the Pacific, three human taeniid species have been recognized: Taenia solium, Taenia saginata and Taenia asiatica. The first topic is on evolution of T. solium. Mitochondrial DNA polymorphisms of T. solium worldwide are discussed with emphasis of two specific genotypes: American-African and Asian. The second topic is recent major advances in sero- and molecular-diagnosis of T. solium cysticercosis in humans, pigs and dogs. The third is the present situation of T. solium taeniasis/cysticercosis in Papua (Irian Jaya), Indonesia. The forth is the present situation of T. solium cysticercosis and T. saginata taeniasis in Bali, Indonesia. The fifth is the present situation of T. asiatica taeniasis in Asia and the Pacific and in North Sumatra, Indonesia. The sixth is on the debate of the exact definition of T. asiatica. Because T. asiatica can not be differentiated from T. saginata morphologically, it is time to re-evaluate T. saginata in Asia and the Pacific. New and broad-based surveys across this region are necessary from epidemiological and public health perspectives, based on evidence.     

Taeniasis/cysticercosis in Bali, Indonesia

Taenia solium and Taenia saginata are found in humans in Bali, Indonesia. During a field survey of 660 people in Bali from 2002-2009 of taeniasis/cysticercosis cases using mitochondrial DNA confirmation of the species, we detected 80 cases of T. saginata taeniasis, 2 dual T. saginata/T. solium infections with T. solium metacestodes in the brain and 12 neurocysticercosis (NCC) cases at Sanglah Hospital, Denpasar. Although the prevalence of NCC in Bali is low, sporadic cases are still present. There is no Taenia asiatica in Bali. We summarize here the field survey findings of taeniasis, including 1 dual infection with taeniasis and cysticercosis in 2007, and the reason why there are no T. asiatica cases and we describe 3 NCC cases admitted to Sanglah Hospital, Denpasar, Bali in 2004. Diagnosis was based on anamnesis, clinical examination, including CT Scan, histopathological, serological and mitochondrial DNA examinations. In order to prevent unexpected symptomatic NCC after treatment with praziquantel, we recommend introducing a rapid test to confirm taeniasis carriers and cysticercosis cases as a tool for real time diagnosis.     

Taeniasis/cysticercosis in a Tibetan population in Sichuan Province, China

The results of a preliminary survey of taeniasis/cysticercosis in Yajiang County, Ganze Tibetan Prefecture in southwest Sichuan Province, China, indicated a very high prevalence of taeniasis (22.5%), with Taenia saginata as the dominant species. There was also a significant occurrence of late-onset epilepsy (8.5% prevalence and 16.4% seropositive for Taenia solium antibodies) attributable in large part to probable neurocysticercosis caused by T. solium. The poor sanitation and hygiene in this Tibetan community likely contributed to a high risk of human cysticercosis despite a low level of T. solium taeniasis (actually no T. solium carriers were detected amongst the 21 proven Taenia carriers). In addition, three taeniasis cases were confirmed by DNA genotyping as Taenia asiatica, which is the first report of this tapeworm in Tibetans, the first report for Sichuan Province and only the third report for mainland China.     

Taeniasis in Mongolia, 2002-2006

Survey on secondary data of taeniasis/cysticercosis was carried out in Mongolia in 2002-2006. A total of 118 taeniid proglottids, a diphyllobothriid segment, and 59 serum samples from 118 taeniasis cases were collected at National Center for Communicable Diseases, Ulaanbaatar, Mongolia. In 2006, 14 serum samples were collected from local people who had histories of epileptic seizures in Selenge Province where pig husbandry was the main business. The 118 proglottids were confirmed to be Taenia saginata by mitochondrial DNA analysis using cytochrome c oxidase subunit 1 and cytochrome b genes. T. saginata taeniasis was widely distributed at least in 10 of 21 provinces. No variation in the nucleotide sequences of the two genes was observed among T. saginata isolates from Mongolia. There was no evidence of Taenia solium taeniasis/cysticercosis or Taenia asiatica taeniasis. A diphyllobothriid segment was confirmed to be Diphyllobothrium latum by mitochondrial DNA analysis.     

A Cross-Sectional Study of Taenia solium in a Multiple Taeniid-Endemic Region Reveals Competition May be Protective

Abstract. We conducted cross-sectional surveys for taeniasis and cysticercosis in humans, pigs, and dogs in four northern provinces of Laos. Human cysticercosis and taeniasis prevalence was 2.2% (95% confidence interval [CI] = 1.4-3.0%) and 8.4% (95% CI = 6.9-9.9%), respectively. Eating uncooked beef, being male, province of residence, age, and ethnicity were significant risk factors for taeniasis and only province of residence was a significant risk factor for cystiercosis. Thirty-five human tapeworms were recovered during the survey and 33 (94.3%) and 2 (5.7%) were identified as Taenia saginata and T. solium, respectively. Maximum-likelihood adjusted prevalence of T. solium and T. hydatigena in pigs was 4.2% (95% CI = 0.5-7.9%) and 55.9% (95% CI = 47.5-64.3%), respectively, and T. hydatigena taeniasis in dogs was 4.8% (95% CI = 0.0-11.3%). Taenia hydatigena and T. saginata were the most prevalent taeniids in the respective pig and human populations and together may suppress T. solium transmission.     

Intestinal cestodes

PURPOSE OF REVIEW: This review summarizes the biology, clinical aspects, diagnosis, treatment and epidemiology for the common and rarer (zoonotic) intestinal cestodes of humans. RECENT FINDINGS: Mass drug application to eliminate Taenia solium carriers may have only temporary effects on cysticercosis transmission. At least two major world genotypes of T. solium have been identified and greater genetic heterogeneity may occur at the regional level. A new human taeniid T. asiatica has been confirmed which occurs sympatrically with T. saginata and T. solium in Southeast Asia. Coproantigen and PCR tests for Taenia spp. have greatly improved diagnostic efficacy and epidemiological studies. There appears to be an increase in human diphyllobothriasis in Europe, Japan and the Americas. SUMMARY: Human intestinal cestode infections are globally primarily caused by species in three genera: Taenia, Hymenolepis or Diphyllobothrium. Sporadic zoonotic infections caused by nontaeniids are usually food-borne or due to accidental ingestion of invertebrate hosts. Intestinal cestode infections generally result in only mild symptoms characterized chiefly by abdominal discomfort and diarrhoea. Most human intestinal cestode infections can be treated with a single oral dose of praziquantel or niclosamide.     

Towards the international collaboration for detection, surveillance and control of taeniasis/ cysticercosis and echinococcosis in Asia and the Pacific

Both cysticercosis and echinococcosis are potentially among the most serious helminth zoonoses threatening human health worldwide. However, due to the lack of reliable tools for confirmation or identification of patients or infected animals, epidemiological data are expected to be underestimated. Conversely, sometimes, such data are over estimated due to the lack of specificity. The most important issue for doing field surveys is that they use evidence based science. In this communication, advanced immunological and molecular tools for detection of individuals infected with either metacestodes or adult tapeworms are briefly overviewed, and the applications of such tools for epidemiological surveys in Indonesia, China and other countries are introduced. As immunological tools are based on antigen-antibody responses, there may exist some cross-reactions. Therefore, immunodiagnostic tools are expected to be useful for primary screening, and should be combined with confirmation of direct parasitological evidence (morphology or DNA), and imaging techniques for cysts. As a risk factor for human cysticercosis is the presence of tapeworm carriers, detection of taeniasis cases and differentiation of the three human Taenia species (Taenia solium, T. saginata and T. asiatica) in Asia and the Pacific requires consideration. Similarly, in northwest China, Echinococcus granulosus and E. multilocularis are coendemic and differentiation of these species is required in humans and definitive hosts. It is stressed that combination of several tools for identification of the parasite and for confirmation of diseases is important for obtaining highly reliable data before consideration of control of these zoonoses. Recent projects coordinated by Asahikawa Medical College have concentrated on immunological and molecular diagnostic techniques transferable to colleagues from endemic regions of Asia and the Pacific, and on organization of two international symposia to establish a platform for further collaboration in the future.     

Human Taeniasis and cysticercosis in Asia

CONTEXT: Human Taeniasis caused by the pork, Taenia solium, or beef, T saginata, tapeworm arises after eating pork or beef contaminated with metacestodes, the larval stage of these parasites. Taeniasis with T solium can lead to neurocysticercosis and threaten others by accidental ingestion of eggs released from asymptomatic Taeniasis patients. The 2003 World Health Assembly declared that T solium is of worldwide public-health importance, and that it is an eradicable parasitic disease worldwide. Adult taeniid tapeworms expelled from people in almost all Asian countries appeared to be T saginata (the so-called Asian Taenia), even though they ate pork. The organism is now named T asiatica, and has been found in Taiwan, Korea, China, Vietnam, and Indonesia. But it has been difficult to differentiate T saginata from beef and Asian Taenia from pork. STARTING POINT: Marshall Lightowlers and colleagues (Int J Parasitol 2003; 33: 1207-17) recently demonstrated that recombinant oncosphere vaccines against several taeniid cestodes, including T ovis, T saginata, T solium, and Echinococcus granulosus, are highly effective. Protection was almost 100%, in the laboratory and in the field. These researchers found several common features, including a predicted secretory signal sequence, and one or two copies of a fibronectin type III domain, each encoded by separate exons within the associated gene. WHERE NEXT? Molecular and immunological techniques, including vaccine research and development of animal models for differentiation of taeniid species in humans, have greatly advanced over the past decade. The clinical importance of infections by these taeniids, including T asiatica, in humans, and the potential for cysticercosis attributable to T asiatica in humans, needs further study.     

Multiple genotypes of Taenia solium--ramifications for diagnosis,treatment and control

Mitochondrial DNA sequences of Taenia solium have fully been analyzed. Analysis of the full length of cytochrome c oxidase subunit 1 (1620 bp) and cytochrome b (1068 bp) genes of T. solium, isolated from Asia (China, Thailand, Indonesia and India), from Latin America (Mexico, Ecuador, Bolivia, Peru and Brazil) and from Africa (Tanzania, Mozambique and Cameroon), has revealed that the two phylogenies obtained were similar to each other regardless of the genes examined. The isolates from Asia formed a single cluster, whereas those from Latin America combined with those from Africa to form an additional cluster. It was estimated that these two genotypes emerged approximately 4-8 x 10(5) years ago. These results together with recent study of the ancient of human taeniid cestodes emerged several MYA in Africa, historical data on swine domestication, distribution of pigs and colonization patterns suggest that T. solium was introduced recently into Latin America and Africa from different regions of Europe during the colonial age, which started 500 years ago, and that T. solium of another origin independently spread in Asian countries, perhaps from China. Why did not T. solium of European origin invade or spread into Asia during the colonial age? Analysis of T. solium distribution must include other Taenia species, especially T. saginata and T. asiatica, which can not be differentiated from each other morphologically. BESS T-base analysis for differentiation of all human Taenia species including the two genotypes of T. solium, and T. saginata and T. asiatica has also been characterized. BESS T-base analysis differentiates African isolates from Latin American isolates as well but more samples should be analyzed for obtaining conclusive evidence for the latter. Serological analysis of cyst fluid of T. solium cysticerci obtained in China and Indonesia and from Mozambique and Ecuador indicates geographical differences in their banding patterns. These differences are discussed in the light of possible differences in pathology of T. solium worldwide. As it has been speculated that the ancient T. solium emerged several million years ago in Africa, it is necessary to analyze more isolates from Africa. Such working hypothesis may be evaluated combined with symptomatology and serology when we get additional DNA data from such areas, since there are some varieties of manifestation of neurocysticercosis with or without subcutaneous cysticercosis and of antigens of cyst fluid of T. solium from Asia and from Africa and/or America. Transfer of techniques of molecular identification and sero- and immuno-diagnoses between researchers and technicians from endemic countries using their own materials should be promoted with the aim of better international cooperation for the control of cysticercosis.     

Community prevalence study of taeniasis and cysticercosis in Bali, Indonesia

Taenia solium, a human cestode parasite endemic throughout most of South-east Asia, causes a number of public health and economic problems. The parasite is endemic in Bali due to a mix of cultural and religious practices. Immunoepidemiological investigation of three rural communities revealed a taeniasis prevalence of 0.72% (3/415). One of the three cases was due to Taenia solium, the other two to Taenia saginata. A further nine cases of Taenia infection were identified from patients from villages surrounding the chosen communities, suggesting that prevalence levels may be higher in other areas. Seroprevalence of human cysticercosis by immunoblot was 1.65% (6/363), though all cases were detected within a single community (6/115; prevalence 5.22%). Several other cases of subcutaneous cysticercosis were identified from local clinics, suggesting continued transmission of Taenia solium in the region. Other intestinal helminth parasites identified within the communities were Ascaris lumbricoides (29.9%), Trichuris trichiuria (33.9%) and hookworm (8.2%).     

Taeniasis vs cysticercosis infection routes

Although cysticercosis caused by Taenia solium(T. solium) is considered a neglected disease, its life cycle has been well known for more than two centuries. T. solium not only causes cysticercosis but also taeniasis in humans. These two diseases have totally different infection routes. To acquire taeniasis(the presence of the adult stage of T. solium in the intestine), humans have to ingest the larval stage(cysticercus) that infects a variety of organs and viscera in pigs, its intermediate hosts. Therefore, taeniasis is acquired when eating raw or undercooked infected pork. The adult stage in the human intestine release eggs that contain a hexacanth embryo, the oncosphere. If humans accidentally ingest the eggs of T. solium, the released oncospheres penetrate the intestine and become cysticerci. Therefore, cysticercosis is acquired by the ingestion of eggs that contaminate water, vegetables, hands etc. These facts should not be forgotten to avoid misinformation in scientific publications.     

Current status of cysticercosis in Vietnam

This English review concerning the current status of cysticercosis in Vietnam has been compiled from various reports of studies conducted over the past 15 years, which have appeared in national publications in Vietnamese, in order to make the information available to the international community. Hospital surveys indicate that cysticercosis is emerging as a serious health problem in the country though most of the information comes from the Hanoi area. Many more men than women are being treated for cysticercosis with most patients being young to middle-aged adults though several juvenile cases have been seen in the south. Clinical manifestations of the disease in humans include subcutaneous nodules, epileptic seizures, severe headache, impaired vision and memory loss. Albendazole has been found to be the best drug for treating cysticercosis though it does not appear to be totally effective for curing cerebral cysts. Information concerning porcine and bovine cysticercosis is very limited and based mostly on passive surveillance at Hanoi slaughterhouses. Surveys for human taeniasis in central and northern provinces indicate a prevalence of 0.2-7.2%. However, techniques of low sensitivity were used and the results are inconclusive since it is unknown with which species of tapeworm the people were infected. In addition to Taenia solium which causes human cysticercosis, T. saginata and T. asiatica are also known to be present in Vietnam. Risk factors investigated thus far with regard to transmission of T. solium suggest that consumption of raw pork, inadequate or absent meat inspection and control, poor sanitation in some areas, and the use of untreated human waste as fertilizer for crops may play important roles in Vietnam but this remains to be validated. The evidence thus far collected suggests that a national surveillance program for cysticercosis is a great need for Vietnam. The authors recommend further research on the epidemiology and impact of cysticercosis in both human and pig hosts in order to determine whether a prevention and control program in Vietnam would be merited and cost effective.     

广西4地带绦虫分离株COX1序列分析

目的 分析广西4地带绦虫分离株COX1序列, 了解亚洲绦虫在广西的分布。方法 对鹿寨、 融水、 田东、 三江等 4县现症病人进行驱虫, 收集绦虫成虫。绦虫成虫经反复洗涤后, 各取孕节一节, 研碎后提取基因组DNA; 同时设计特异性引物, PCR扩增各分离株COX1片段, 对扩增产物进行T?A克隆测序; 应用相关软件分析序列的同源性、 遗传距离, 同时构建系统发生树。同时, 从GenBank检索亚洲绦虫、 猪带绦虫和牛带绦虫COX1基因序列, 并与4地分离株基因序列进行比较。结果 广西4地5个带绦虫分离株的COX1碱基序列长度均为444 bp。鹿寨株与亚洲绦虫之间基因差异为5个位点（1.11%）, 同源性为98.87%, 遗传距离为0.011, 其在邻接法和简约法构建的系统发生树中位于同一分枝。融水A株与猪带绦虫同源性达100%, B株与牛带绦虫和亚洲绦虫的同源性分别达98.20%和96.17%; 田东和三江分离株与猪带绦虫的同源性分别为99.55%和96.40%, 遗传距离分别为0.005和0.037; 鹿寨株与牛带绦虫的同源性达96.40%。结论 广西鹿寨县存在亚洲绦虫流行, 融水县存在牛带绦虫和猪带绦虫混合流行。     

Development of a serologic assay to detect Taenia solium taeniasis

We developed a serologic assay to identify adult Taenia solium tapeworm carriers using excretory/secretory (TSES) antigens collected from in vitro cultured T. solium tapeworms. To identify taeniasis-specific antigens we used an immunoblot assay with serum samples from T. solium tapeworm carriers and cysticercosis patients. Antigens were identified that reacted with antibodies present in serum samples from taeniasis cases and not with those from cysticercosis patients. Using serum samples collected from persons with confirmed T. solium tapeworm infections, the test was determined to be 95% (69 of 73) sensitive. Serum samples (n = 193) from persons with other parasitic infections, including T. saginata tapeworm infections, do not contain cross-reacting antibodies to TSES, indicating that the assay is 100% specific. These data suggest that the immunoblot assay using TSES antigens can be used to identify persons with current or recent T. solium tapeworm infections and provides a new, important tool for epidemiologic purposes, including control and prevention strategies.     

分子分类结合形态学方法对云南大理带绦虫的鉴定

目的 鉴定云南大理洱源(E1-E2)、鹤庆(H1-H2)、双廊(SL)、挖色(WS)带绦虫的种.方法 首先对大理分离株带绦虫成虫进行形态学鉴定,从成虫节片中抽提DNA,PCR扩增线粒体DNA细胞色素B(mtDNA-Cyth)的部分序列并测序;结合GenBank中已知猪带绦虫、牛带绦虫和亚洲带绦虫mtDNA-Cytb序列,经DNAMAN软件处理后构建系统发育树状图.结果大理带绦虫E1的形态和牛带绦虫相似,系统发育树显示大理分离株E1、E2、SL、WS带绦虫标本与亚洲带绦虫的遗传距离最接近,距牛带绦虫较远,与猪带绦虫则更远.大理分离株H1、H2带绦虫标本与猪带绦虫的遗传距离最近,距牛带绦虫和亚洲带绦虫则较远.结论 经形态学和分子生物学鉴定,云南大理分离株E1、E2、SL、WS带绦虫标本属于亚洲带绦虫,而H1、H2株带绦虫标本属于猪带绦虫.     

Short report: secondary transmission in porcine cysticercosis: description and their potential implications for control sustainability

Taenia solium taeniasis/cysticercosis is one of few potentially eradicable infectious diseases and is the target of control programs in several countries. The larval stage of this zoonotic cestode invades the human brain and is responsible for most cases of adult-onset epilepsy in the world. The pig is the natural intermediate host, harboring the larvae or cysticerci. Our current understanding of the life cycle implicates humans as the only definitive host and tapeworm carrier (developing taeniasis) and thus the sole source of infective eggs that are responsible for cysticercosis in both human and pigs through oral-fecal transmission. Here we show evidence of an alternative pig-to-pig route of transmission, previously not suspected to exist. In a series of four experiments, naive sentinel pigs were exposed to pigs that had been infected orally with tapeworm segments (containing infective eggs) and moved to a clean environment. Consistently in all four experiments, at least one of the sentinel pigs became seropositive or infected with parasite cysts with much lower cyst burdens than did primarily infected animals. Second-hand transmission of Taenia solium eggs could explain the overdispersed pattern of porcine cysticercosis, with few pigs harboring heavy parasite burdens and many more harboring small numbers of parasites. This route of transmission opens new avenues for consideration with respect to control strategies.     

家畜动物及鼠类之囊虫病(英文)

目的猪囊虫、牛囊虫及台湾绦虫、囊虫,分别为人体绦虫之有钩条虫、无钩条虫及亚洲无钩绦虫之幼虫。猪囊虫流行在美洲、欧洲及亚洲,牛囊虫分布于非洲、美洲及亚洲,台湾绦虫囊虫流行于亚洲。猪囊虫天然传染来源是猪,牛囊虫是牛,猪囊虫及牛囊虫寄生之适宜部位于肌肉,而台湾绦虫囊虫寄生之部位为肝脏。此三种绦虫之潜伏期依次为60-70天,60-75天及28天。猪囊虫生活期最长,惟牛囊虫及台湾绦虫囊虫在猪体仅生活数日,同时极多数牛囊虫及台湾绦虫囊虫在牛体仅生活数日。上述三种囊虫在鼠体能长期生存。猪囊虫及牛囊虫经过血管及淋巴管可移行入小肠壁,然后进入体肌,同时台湾体虫囊虫经过血管移行人小肠壁,然后进入肝脏。普瑞斯夸陶治疗囊虫病之最低有效剂量,每kg体重服用100 g,连续服用3天。     

四川省凉山彝族地区囊尾蚴病血清学调查(英文)

目的了解四川省凉山州彝族地区囊尾蚴病感染情况和流行风险因素。方法于2006年对凉山州昭觉县比尔乡的部分居民问卷调查;猪带绦虫尾蚴GPs作为抗原,用ELISA方法检测人、猪血清猪囊尾蚴特异性抗体。结果当地居民继发型癫痫发作率为9.1%(57/626),人、猪血清阳性率分别为7.2%(36/499)、13.9%(14/101)。该病在当地流行的主要原因包括猪放养、不良食肉习惯(坨坨肉)、人无厕所、肉品检疫不严以及经济落后等。结论囊尾蚴病高度流行于四川省彝族地区。为控制该病的流行,必需采取综合性的防治措施,如主动的人群绦虫病筛查和治疗、加强肉食品检疫和人粪管理、改变不良饮食习惯、提倡猪圈养等。     

Taenia solium taeniasis and cysticercosis in three communities in north Vietnam

OBJECTIVES: (1) To investigate the response to a serum antigen-detecting ELISA for cysticercosis and a stool coproantigen test for taeniasis in two rural communities (mountainous and coastal areas) and one group of (peri-)urban factory workers; and (2) to examine clinical features of human cysticercosis in northern Vietnam. METHODS: Villagers and factory workers and their families were informed and invited to participate in the study. Blood and faecal samples were collected from the participants and a simple questionnaire on taeniasis/cysticercosis completed. Serum was examined for the presence of circulating cysticercus antigen by a monoclonal-based sandwich ELISA. Ag-ELISA positive persons underwent a clinical examination and a computed tomography (CT) scan. Stool samples were examined microscopically for the presence of Taenia eggs and for copro-antigens. Tapeworms were identified following therapeutic expulsion using morphology and PCR-RFLP. RESULTS: Circulating cysticercus antigens, suggesting active infection, were detected in 5.3% (16/303), 0.6% (1/175) and 0.0% (0/229) of the sampled individuals from the mountainous, coastal and urban regions, respectively. Clinical examination and CT scan of the cysticercus antigen positive persons showed that active cysticercosis did not cause severe disease in most cases. Taenia copro-antigens were found in 0.3% (1/297), 1.8% (3/166) and 0.0% (0/228) of the stool samples from the mountainous, coastal and urban communities, respectively. Three tapeworms were expelled after treatment: two Taenia solium and one Taenia saginata. CONCLUSION: This survey points to a focal distribution of taeniasis/cysticercosis and suggests that human cysticercosis is rather acquired due to close contact with a T. solium carrier and self-infection, than through infection from the environment.     

河南省消除试点医务人员猪带绦虫病和囊尾蚴病防治知识培训效果

目的 了解培训前后河南省方城县消除试点医务人员猪带绦虫病和囊尾蚴病防治知识知晓率变化,评估培训效果.方法 选取方城县独树镇、博望镇和杨集乡为干预乡(镇),2016-2020年每年对干预乡(镇)基层医务人员开展1次猪带绦虫病和囊尾蚴病防治知识培训;选择二郎庙乡、杨楼乡和小史店镇作为对照乡(镇),不开展培训.抽取干预乡(镇...