The epidemiology of Echinococcus granulosus in Great Britain. V. The status of subspecies of Echinococcus granulosus in Great Britain

Twenty-five years ago Williams and Sweatman suggested that in Great Britain there are two subspecies of Echinococcus granulosus--E. granulosus granulosus and E. granulosus equinus. Echinococcus granulosus granulosus does not mature either in foxes or in horses: E. granulosus equinus will mature in either. The prepatent period of E. granulosus granulosus in the definitive host is about 42 days while that of E. granulosus equinus is about 70 days. Each subspecies has a characteristic morphology. More recently, in the course of seven experiments, dogs, red foxes (Vulpes vulpes crucigera), arctic foxes (Alopex lagopus), badgers (Meles meles), domestic ferrets and domestic cats have been infected with protoscoleces derived from hydatid cysts of human, equine and ovine hosts from different regions of England and Wales. Transmissions to horses and sheep were always succeeded by the development of viable hydatid cysts; transmissions to dogs and foxes, by the development of gravid adults. The prepatent period in both dogs and foxes was invariably about 70 days (or longer) and the morphology of all the adult parasites in these definitive hosts was characteristic of E. granulosus equinus. All the evidence derived from these experiments supports the view that there is, in Great Britain, but one subspecies of E. granulosus. That one subspecies is E. granulosus equinus. It infects dogs, red foxes, arctic foxes (experimentally), cats (experimentally), humans, sheep, goats, horses, donkeys, pigs, cattle, roe deer and reindeer (in Scotland). Attempts to transmit E. granulosus to badgers and domestic ferrets were unsuccessful. Of 123 cats infected with protoscoleces of horse origin, one gravid adult parasite was recovered from one animal.     

The prevalence of Echinococcus granulosus in stray dogs in Iraq.

The present paper records the prevalence of Echinococcus granulosus in stray dogs of Al-Tamim (northern Iraq), Diala (mid Iraq) and Theqar province (southern Iraq), where many people are infected with hydatid disease. Of 150 dogs examined in three provinces in Iraq, 57 (38%) were infected with E. granulosus. The prevalence of the worm was higher in the dogs of Theqar province (56%) than in those of Al-Tamim (20%) and Diala Provinces (38%). Infections were light (1-200 worms) in eight (14%) of the infected dogs, medium (201-1000 worms) in 14 (24.6%) and high (over 1000 worms) in 35 (61.4%). The mean worm burden was 1844 and the maximum number of worms was 15,182 recorded in a male dog from Theqar province. The reasons for such a high rate of infection in the dogs are discussed.     

Experimental infection of Libyan sheep with Echinococcus granulosus.

The growth rate of unilocular hydatid cysts over a two-year period was studied in Libyan sheep dosed orally with gravid segments of Echinococcus granulosus taken from stray town dogs. Seven of the eight sheep dosed with 20-100 gravid segments (say 4000-20,000 eggs) had developed only infertile hydatid cysts after 107-611 days. Sheep dosed with 1000 gravid segments (say 200,000 eggs) had developed only sterile cysts when examined 358 days after dosing. Fertile cysts were recovered from the lungs after 428 days, and after 584 days from the liver. Only sterile cysts were seen in the heart, spleen and kidneys.     

Specific antibody responses in dogs experimentally infected with Echinococcus granulosus

Six dogs reared helminth-free were divided into 2 groups. Four dogs were infected per os with 200,000 protoscoleces each of Echinococcus granulosus and 2 were kept as uninfected controls. All the dogs were kept together until 32 days after infection, when 1 infected dog was killed, its intestine removed and the contents examined to confirm that the infection with E. granulosus had been successful. The remaining 3 infected dogs were transferred to high security housing and their feces inspected daily to establish the time infections became patent. The infected and control dogs were bled every 5 days for 75 days from the time of infection and the sera were stored at -70 degrees C. Sera were tested by the enzyme-linked immunosorbent assay (ELISA) for antibodies to E. granulosus scolex excretory/secretory (ES) antigen, protoscolex antigen and oncosphere antigen. Antibodies to scolex ES antigen and protoscolex antigen were detected in the sera of infected dogs within 2 weeks of infection. Antibody titers rose rapidly and remained at a high level until the dogs were killed 75 days after infection. Antibodies in these sera did not cross react with antigens prepared from Taenia ovis, T. hydatigena, T. pisiformis, Ancylostoma caninum, Trichuris vulpis and Toxocara canis.     

Frequency distributions of Echinococcus granulosus and other helminths in stray dogs in Tunisia

The intestinal helminths infecting stray dogs were investigated in the Testour and Bouzid regions of Tunisia. Overall, 21% of the dogs necropsied were found to be infected with Echinococcus granulosus. The prevalence among the animals from Testour (27.0%) was significantly higher than that in the dogs from Bouzid (6.9%). Although the prevalence of this species in the dog populations did give a significant fit to the age-prevalence models reported earlier, the best fit was not consistent with the known biological parameters of the parasite. The frequency distribution of E. granulosus was highly aggregated, with a mean abundance of infection of 538 parasites/host and a mean intensity in infected animals of 2534 parasites/host. Several Taenia species were also found in the dogs, but none of these showed evidence of an aggregated distribution and the frequency distribution of each fitted a Poisson distribution, which is unusual for naturally acquired infections. All the other cestode species and the nematode species encountered had aggregated distributions in the dogs. As there was relatively little correlation between the worm burdens of the different parasite species in the dogs, individual dogs may not be generally susceptible or resistant to intestinal helminths of several species.     

Echinococcus granulosus and Echinococcus multilocularis invasions in north-eastern Poland

During the last 10 years 70 cases of echinococcosis were diagnosed in the Department of Infectious Diseases, Medical University School of Bia?ystok, of whom 63 were Echinococcus (E.) granulosus infections. The Urban population (70%) and women (60%) dominated among infected persons. Seven cases were due to E. multilocularis infection. A family and endemie focus of E. multilocularis human invasion has been identified.     

Prevalence and public health implications of Echinococcus granulosus in rural dogs in Eastern Nigeria

Prevalence of Echinococcus granulosus infection in rural dogs in Eastern Nigeria was determined. Of the 182 dogs examined, 8 (4.4%) had Echinococcus granulosus infection. The number of Echinococcus granulosus recovered was 80, of which 16 (20%) were from faeces and 64 (80%) were derived from intestinal mucosa. Of the localities surveyed, Eke-Uke had the highest number of infected dogs, 13 out of 38 (34.3%). The females accounted for 94 out of 182 dogs (51.6%) examined, while 98 (53.8%) were males. E. granulosus was present in 7 out of 94 (7.4%) females and in 10 out of 98 (10.2%) males. Parts of the body of thd dogs (anal region, outside of the mouth and coat) examined were positive for taeniid ova. Other cestodes recovered were Taenia hydategina, Taenia ovis, and Taenia pisiformis.     

犬体内细粒棘球绦虫和多房棘球绦虫的混合感染

目的 证实家犬体内是否存在细粒棘球绦虫和多房棘球绦虫混合感染。方法 从新疆和静县巴音布鲁克草原现场收购的30条牧羊犬,经麻醉后处死解剖,在1只雌性牧羊犬小肠内发现棘球绦虫成虫1万条以上,经显微镜观察,疑为细粒棘球绦虫和多房棘球绦虫混合感染。用Eg1f/r和EM-15/17EM引物分别对两种棘球绦虫的线粒体DNA特异目的片段进行序列分析鉴定。结果 形态学观察:细粒棘球绦虫孕节长大,生殖孔偏后,位于节片一侧中部。子宫有不规则的分支和侧突(侧囊),内含虫卵200~800个。多房棘球绦虫较短小,4~5体节。孕节中子宫呈简单的囊状,无侧囊。生殖孔开口于侧缘的前半部。线粒体12S RNA序列鉴定,扩增样本DNA经同源序列比较发现,与细粒棘球绦虫G1型具有相同的序列;扩增样本与多房棘球绦虫具有相同的序列。分别确定为细粒棘球绦虫和多房棘球绦虫两种虫种。结论 首次证实家犬体内存在细粒棘球绦虫和多房棘球绦虫的混合感染。     

The Echinococcus granulosus antigen EgA31: localization during development and immunogenic properties

EgA31 is a fibrillar protein from Echinococcus granulosus that behaves as a potent antigen during infestation of dogs. The localization of this antigen during development of the parasite was investigated by immunohistochemistry in optical and electron microscopy. The protein is mostly abundant in the microtriches and subtegumental cells of the adult, whereas it is absent from protoscolex microtriches. Eggs, the periphery of calcareous corpuscles, and the germinal layer were other sites of accumulation. Immunogenicity of different domains of the protein was assessed during experimental infection of dogs. It was shown that the polypeptide encoded by the Pst I-Hind III fragment of the complete cDNA is the most antigenic during the infection. The uses of such polypeptide for infection diagnosis and as a candidate vaccine protein are discussed.     

细粒棘球绦虫核糖体蛋白S9基因克隆鉴定及其在不同发育阶段表达分析

目的克隆鉴定细粒棘球绦虫原头蚴核糖体蛋白S9基因,分析其在细粒棘球绦虫不同发育阶段的表达情况。方法从已构建的cDNA文库挑选基因,克隆EgRPS9基因并对编码产物的理化性质、功能位点、蛋白质的结构和功能域进行预测和分析,通过RealTime-PCR检测RPS9基因在细粒棘球绦虫不同发育阶段的表达情况。结果通过各种生物数据库对EgRPS9基因进行预测并测序,显示该基因具有完整开放阅读框,大小为564bp,编码188个氨基酸,预测分子质量单位为22.0ku,等电点为10.32。SMART保守功能区域分析发现该基因第107~149个氨基酸为40S亚基S9结构域S4超家族。通过多序列比对发现该基因具有较高的保守性,进化树结果表明该基因与曼式血吸虫、日本血吸虫及华氏睾吸虫亲缘关系较近。Real time-PCR检测原头蚴和囊泡RPS9基因相对表达量分别为1.16和1.02,差异无统计学意义(P>0.05)。结论成功克隆出细粒棘球绦虫40S亚基RPS9新基因,该基因在细粒棘球绦虫不同发育阶段均有表达。     

细粒棘球蚴感染中国美利奴羊免疫指标的动态变化

目的检测分析绵羊感染细粒棘球蚴免疫指标的变化。方法用细粒棘球蚴对14只健康的中国美利奴羊在相同的条件下进行人工感染,在感染前7d(-7d)、感染当天(0d)、感染后7d、21d、30d、60d用流式细胞仪分析外周血中CD4+T、CD8+T、B淋巴细胞亚群的动态变化,同时检测血清中IgG、IgM、IgE、IFN-γ水平和粒细胞数量。结果进行人工感染的14只绵羊中有8只感染(感染组),6只未感染(未感染组);CD4+T细胞在攻虫后第7d、30d未感染组显著高于感染组(P<0.05)。CD8+T细胞和B淋巴细胞两组之间差异不显著(P>0.05);IgG和IgE水平在攻虫后第30d未感染组显著高于感染组(P<0.05)。IFN-γ水平在攻虫后第21d、30d未感染组显著高于感染组(P<0.05);淋巴细胞在攻虫后第21d(P<0.01)、30d(P<0.05)未感染组显著高于感染组。嗜中性粒细胞在攻虫后第21d感染组极显著高于未感染组(P<0.01)。结论中国美利奴羊感染细粒棘球绦蚴过程中,CD4+T细胞、IgG、IgE、IFN-γ和淋巴细胞水平升高可增强机体对细粒棘球蚴的抵抗力。     

Identification of protein components of Echinococcus granulosus protoscolex antigens for specific serodiagnosis of E. granulosus infection in dogs

Proteins of Echinococcus granulosus protoscolex excretory/secretory or deoxycholate solubilized somatic antigens were radiolabelled with 125I and immunoprecipitated with sera from dogs naturally or experimentally infected with E. granulosus and various control dog sera. Analysis of immunoprecipitates was performed using one- and two-dimensional gel electrophoresis to identify antigenic protein components specific for E. granulosus. Using both electrophoretic techniques, a basic component of Mr 27,000 and an acidic component of Mr 94,000 were defined in both excretory/secretory and somatic protoscolex antigens, and were specifically identified by 95% and 62% of 21 sera from E. granulosus-infected dogs, respectively. An abundant component of Mr 35,000 was identified by 100% of these dogs, parts of which were E. granulosus specific. Results of this study should allow identification of specific recombinant antigens for routine serodiagnosis of E. granulosus infection in dogs.