Infection of normal C3H/HeN mice with Taenia saginata asiatica oncospheres

Normal C3H/HeN female mice were used to develop an animal model of Taenia saginata asiatica oncosphere infection. The host cellular immune response in this model was analyzed by a cytokine enzyme-linked immunosorbent assay (cytokine ELISA) and flow cytometry. Tumor-like cysts containing cysticerci were recovered from the inoculation sites of female mice 7 weeks postinfection with the T. saginata asiatica oncospheres. A sharp increase and sustained elevation in the ability of spleen cells to produce interferon-γ and interleukin (IL)-2 revealed that cellular immunity played an important role during the infection. An immediate increase in the levels of IL-6 at 1 week postinfection indicated the induction of a local acute inflammatory response. However, no significant change in the levels of IL-10 indicated that Th2 cells were not involved in this immune response. The patterns of cell distribution revealed by flow cytometry also supported the same finding. These results suggested that Th1 cells played a major role in the immune response in C3H/HeN mice during the early stages of the oncosphere infection and that the Th2 response was not induced during the stage of cysticercus formation.     

Taenia saginata in Europe

In spite of the EU directives that regulate meat inspection for bovine cysticercosis, Taenia saginata is still present in Europe and causes economic losses due to condemnation, refrigeration and downgrading of infected carcasses. The main reasons for this persistence include the low sensitivity of current meat inspection protocols, the dissemination and survival of eggs in the environment and cattle husbandry systems, which allow grazing on pastures and drinking from water streams. It is assumed that water streams and surface water are potentially contaminated with T. saginata eggs. Furthermore, current wastewater management not only fails to halt, but rather contributes to the dissemination of eggs in the environment. Here, the authors discuss an integrated approach for control of this food-borne zoonosis, as well as the potential use of serological methods as a way of improving detection of bovine cysticercosis.     

In vivo cross-reactivity of Taenia saginata and Taenia crassiceps antigens in bovine cysticercosis

Steers sensitized or infected with Taenia saginata exhibited similar delayed-type dermal hypersensitivity (DTH) responses after intradermal inoculation with T. saginata or T. crassiceps skin test antigens. Steers sensitized to T. crassiceps cysticerci exhibited similar DTH responses to intradermal inoculation with T. crassiceps, T. saginata whole worm and T. saginata cysticerci antigens. No correlation existed between the DTH responses and the number of cysticerci in the carcasses. One sensitized/infected and one infected steer harbored cysticerci but exhibited no DTH responses. Infection with cysticerci did not elevate DTH responsiveness in sensitized animals.     

Host serum proteins in Taenia saginata metacestode fluid

Taenia saginata cyst fluid was examined for host proteins; IgG1 and IgG2 as well as haemolytic complement activity were detected. Polyacrylamide gel electrophoresis revealed differences in proteinograms among the samples taken from 1-, 4-, and 10-month old cysts. Fluid from older cysts had fewer protein components and showed a weaker antigenic reaction with sera of bovines infected with T. saginata than that of younger cysts. The roles of antibody and complement in initiating degeneration of the parasite are discussed.     

Sero-epidemiological study of Taenia saginata cysticercosis in Belgian cattle

A sero-epidemiological survey of Taenia saginata cysticercosis was carried out to determine the prevalence of the infection in cattle presented for slaughter in Belgium. Between November 1997 and June 1998, a total of 1164 serum samples were collected in 20 export abattoirs. Meat inspection was routinely carried out by veterinary inspectors. Serum samples were examined for circulating parasite antigen using a monoclonal antibody-based sandwich enzyme-linked-immunosorbent assay (Ag-ELISA). Thirty six serum samples (3.09%) were found positive in the Ag-ELISA, while by meat inspection on the same animals cysticerci were detected in only three carcasses (0.26%). Sero-prevalence was positively correlated with the age of the animals. The sero-prevalence found in this study was more than 10 times higher than the annual prevalence (0.26%) reported by the Institute for Veterinary Inspection. This study clearly indicates that the classical meat inspection techniques detect only a minor fraction of the carcasses infected with cysticerci.     

Effect of Paecilomyces lilacinus on the viability of oncospheres of Taenia hydatigena

Paecilomyces lilacinus (Thom) Samson is a saprophytic hyphomycete from the soil with biological activity on helminth eggs. We evaluated the influence in vitro of P. lilacinus on the viability of the oncospheres from Taenia hydatigena, a parasite cestode of dogs and sheep. The eggs were exposed to the fungus strain in sterile distilled water and observed by light microscopy at days 4, 7 and 14 post-inoculation, and the viability was evaluated. The viability found in the exposed P. lilacinus oncospheres was significantly different in all observations. P. lilacinus exercised a negative biological activity on T. hydatigena eggs in vitro.     

Taenia saginata cysticercosis in an Ohio cattle feeding operation

In January to March 1981, 37 slaughter cattle from a single Ohio feeding operation were determined, at postmortem inspection, to be infected with Taenia saginata cysticerci. A subsequent outbreak on this same farm in March 1983 involved 7 slaughter cattle. An epidemiologic investigation was conducted of possible sources of the T saginata ova; these included leakage of raw sewage onto the pasture after a flood in 1980, municipal sewage sludge application on the farm, defecation in feed or water by farm workers, and other off-farm sources. Temporal and spatial observations implicated raw sewage contamination of pastures as the most likely source of infection in the 1981 outbreak. The outbreak in 1983 was more likely associated with sludge application. The possibility of an infected worker exposing the cattle to infected feces was not excluded definitely as a possible source.     

Clinico-pathological studies in cattle experimentally infected with Taenia saginata eggs

Calves 1-2 months old were experimentally infected with eggs of Taenia saginata and clinical and haematological deviations, development and distribution of cysticerci and pathological changes were recorded. The calves infected with 5,000, 10,000 or 50,000 eggs showed an increase in pulse and respiratory rates. The animals that received 50,000 eggs had significantly increased pulse (p < 0.05) and respiratory rates (p < 0.005). The symptoms were more severe in young, 30-day-old calves infected with 50,000 eggs. Haemoglobin concentration, haematocrit values and red blood cell count decreased, but white blood cell count increased slightly. Lymphocytes and eosinophils also increased up to 88% and 14% (p < 0.05), respectively. Most of the cysticerci were not fully formed 1 month post-infection, but at 2 months the cysts were fully mature and at 4 months, some cysts had degenerated. There was no uniform pattern of distribution of cysticerci in the body of infected calves, but the most commonly affected sites were masseter and heart muscles, followed by diaphragm, tongue and other skeletal muscles. The maximum concentration of 8-14 cysticerci per 10 g of tissue was recorded in masseter muscles and heart. The affected parts revealed tissue reactions that included pressure atrophy, necrosis and fibrosis. Microscopically, the lesions comprised infiltration with lymphocytes, plasma cells, eosinophils and macrophages, fibrosis, necrosis and calcification. The tissue reaction was severe in calves infected with 50,000 eggs. The severity of clinical signs, haematological and pathological changes depended mostly on the age of the animals and dose of infection.     

Identification of antigens for use in immunodiagnosis of Taenia saginata cysticercosis

Fifteen metacestode antigens from Taenia saginata were defined by Laurell crossed immunoelectrophoresis and investigated for their potential use in immunodiagnosis of bovine cysticercosis. Several antigens cross reacted with those of some common cattle parasites. Three of the antigens, designated as numbers 4, 8 and 11, were selected on the basis of their restricted cross reactions and were isolated by affinity chromatography. These antigens showed high sensitivity and specificity values in the enzyme-linked immunosorbent assay (ELISA) for serodiagnosis of bovine cysticercosis.     

Effect of intraperitoneal inoculation of mebendazole on Taenia saginata cysticercosis in calves

Mebendazole was injected intraperitoneally at a dose of 40 mg/kg into six calves that had been inoculated 6 weeks earlier with eggs of T. saginata. The lethal effect of the drug on cysticerci was not significant in the mebendazole treated animals in comparison with those treated with a placebo. This was evaluated by counting the total number of cysticerci in each calf and the relative numbers of viable and degenerated cysts, an in vitro test for viability of cysticerci, and histological examination of the infected muscle tissue.     

A study on the survival of Taenia saginata eggs on soil in Denmark

The infectivity of Taenia saginata eggs exposed to environmental conditions on a natural soil surface in Denmark was studied by feeding the eggs to susceptible calves, followed by determination of the number of cysts developed. The results indicated that a small proportion of the eggs remained infective for 6 1/2 months, but not for 9 1/2 months when deposited in May 1986, and for 5 1/2 months but not for 8 1/2 months when deposited in September 1987. Viability of eggs was tested in vitro and compared with infectivity obtained in calves.     

Serum antibody levels to Taenia saginata in cattle grazed on Scottish pastures

The serum antibody levels to Taenia saginata of three groups of cattle were assessed by an enzyme-linked immunosorbent assay (ELISA). The first group of cattle were from four farms which had a confirmed T saginata cysticercosis outbreak, all of which had cattle classed as infected by ELISA. The second group were from four farms where sewage sludge had been applied to pasture subsequently grazed by the cattle. One of these farms had cattle classed as infected by ELISA. The control cattle, which were all classed as uninfected by ELISA, came from five farms whose pasture had not been treated with sewage sludge. In a wider survey, involving sera from 47 additional farms, the majority could not be distinguished from the control farms in the earlier survey. However, samples from three of the farms had a similar number of positives to two of the known infected farms in the initial survey. Since the ELISA assay may indicate infected herds, farms such as these warrant further investigation.     

豆状带绦虫六钩蚴Tp-dUTPase基因的表达及血清学诊断效果

采用PCR方法从豆状带绦虫六钩蚴中扩增得到Tp-dUTPase基因编码区,构建了pET32a-Tp-dUTPase原核表达载体,以重组蛋白dUTPase作为包被抗原建立的兔豆状囊尾蚴病Dot-ELISA诊断方法对226份兔血清进行了检测。结果显示,Tp-dUTPase基因编码区长447bp,编码148个氨基酸,表达的重组蛋白相对分子质量为36 200,该重组蛋白能与家兔豆状囊尾蚴病阳性血清特异性结合。以重组蛋白Tp-dUTPase作为包被抗原建立的Dot-ELISA诊断方法显示有较高的特异性（85.7%~92.9%）和敏感性（86.4%~88.0%）,与其他种类兔寄生虫病阳性血清有较低的交叉反应。结果表明,纯化的Tp-dUTPase重组蛋白可作为兔豆状囊尾蚴病的诊断抗原。