Risk factors associated with porcine cysticercosis in selected districts of Eastern and Southern provinces of Zambia

To determine the risk factors associated with Taenia solium transmission in humans and pigs in the rural areas of Eastern and Southern provinces of Zambia, a questionnaire was administered in 788 households from 155 villages. Pigs were examined from 800 households. Tongue examination and enzyme-linked immunosorbent assay (Ag-ELISA) for the detection of circulating antigens of T. solium cysticerci were used to measure infection in pigs. A snowballing technique was utilised to select households with pigs. Prevalence of households with pigs infected with T. solium on tongue examination by district ranged from 12.7% to 32.1% with Ag-ELISA having a range of 30.0-51.7%. Of the total number of households visited, 18.8% and 37.6% had at least one pig positive for porcine cysticercosis on tongue examination and Ag-ELISA, respectively. Risk factors associated with T. solium infection were lack of pork inspection at slaughter (96.7%), consumption of pork with cysts (20.1%), selling of pork infected with T. solium cysticerci (18.3%), free-range husbandry system (83.2%) and absence of latrines (58.0). Free-range husbandry system (OR=1.68; 95% CI=1.36-2.07) was a significant risk factor for porcine cysticercosis in the surveyed areas. The result that pigs were mostly kept on free-range and semi-intensive husbandry systems may have permitted them to have access to eating human faeces that could be contaminated with tapeworm eggs. This study has shown that T. solium infection poses a high public health risk in the study areas and urban areas as well. We recommend that a human survey be conducted to verify the human exposure to taeniasis and/or cysticercosis in Zambia.     

Comparative evaluation of an indirect ELISA test for diagnosis of swine cysticercosis employing antigen from Taenia solium and Taenia crassiceps metacestodes

Taenia solium cysticercosis is still a serious public health problem in several countries where poverty and lack of hygiene favor transmission. Because pigs are the primary intermediate hosts, prevalence of porcine cysticercosis is a reliable indicator of active transmission zones. Serological diagnostic methods are important tools for epidemiological studies since they can be applied to living animals on a large scale. Four antigen preparations (cyst fluid and crude) from T. solium and T. crassiceps metacestodes were compared for swine cysticercosis diagnosis by indirect ELISA (IE). Twenty-eight serum samples from swine naturally and experimentally infected by cysticerci of T. solium and 56 serum samples from swine reared in commercial herds were tested. Best results of overall sensitivity were obtained by the use of cyst fluid and crude antigen of T. crassiceps metacestode (100 and 96.4%, respectively). Using homologous antigen preparations we have observed higher specificity percentage (98.2% for cyst fluid and 96. 4% for crude metacestode T. solium antigen). We concluded that sensitivity is of far more importance than specificity for identification of endemic areas in order to prevent transmission to man. We conclude, therefore, that IE performed with cyst fluid antigen of T. crassiceps metacestode is a better tool for that purpose.     

猪囊尾蚴重组抗原和基因工程疫苗的研究进展

猪囊尾蚴病（Cysticercosis）是由猪带绦虫的幼虫囊尾蚴寄生于人或猪等而引起的人畜共患寄生虫病,是公认的世界经济病之一。严重威胁着人体健康,并给畜牧业造成重大经济损失,猪囊尾蚴病的免疫防治势在必行。然而在猪囊尾蚴病疫苗研究中,疫苗抗原的选择和来源一直困扰着兽医工作者。该文就近年来猪囊尾蚴病诊断重组抗原和基因工程疫苗的分子生物学研究进展进行了综述。     

Castration and pregnancy of rural pigs significantly increase the prevalence of naturally acquired Taenia solium cysticercosis

Cuentepec is a rural village of central Mexico, where 1300 pigs were bred at the time of the study in conditions that favor Taenia solium transmission. The tongues of 1087 (84%) of these pigs were visually examined and 33% were found to be cysticercotic. Castration of male pigs increased prevalence from 23 to 50% (P < 0.001) and pregnancy in sows also increased their prevalence from 28 to 59% (P < 0.001). Thus, endocrinological conditions characterized by low levels of androgens or high levels of female hormones probably influence the susceptibility of pigs to T. solium cysticercosis as observed in mice infected with Taenia crassiceps. Delaying castration of male pigs and confinement of sows during pregnancy might significantly decrease the prevalence of pig-cysticercosis and help curb transmission without much cost or difficulty.     

青海省猪囊尾蚴病血清学调查

猪囊尾蚴病又称猪囊虫病,是由人的有钩绦虫(猪带绦虫)的幼虫——猪囊尾蚴寄生在猪的肌肉中所引起一种人畜共患寄生虫病。为了摸清青海省猪囊尾蚴感染情况,对来自10个县市的788份猪血清样品采用ELISA方法进行了血清学检测,结果检出阳性样品17份,阳性率为2.16%。     

Chemotherapy of porcine cysticercosis with albendazole sulphoxide

Cysticercosis is a zoonotic disease of humans produced by the larval stage of swine parasite, Taenia solium. Chemotherapy of infected pigs is a possible strategy for avoiding disease transmission and improving health programs in endemic areas of cysticercosis. In this preliminary study, seven naturally infected pigs from 6 to 12 months of age were allotted to treated (n = 4) and control groups (n = 3). The treated animals received a subcutaneous injection in their forelegs and thighs of 15 mg/kg per body weight of albendazole sulphoxide (ABZSO; Pisa, Mexico) once per day for 8 days. At the same time, the control group received a subcutaneous injection of saline solution (9% NaCl). After 12 weeks, all the animals were slaughtered and at least 200 metacestodes were isolated from the muscles and brain of each animal. Using histology and the metacestode viability criteria described in this study, treated animals had no viable cysts in their muscle (0/200), while 7 of 17 (41.1%) viable cysts were observed in those isolated from their brains. In the control group, 183/200 (91.5%) muscle metacestodes were viable and from brain, 22/29 (75.8%) metacestodes were viable. The 15 mg/kg per body weight dosage of ABZSO was 100% effective against muscular cysticercosis as shown by the lack of viable cysts and the micro-calcifications in meat from the treated pigs.     

A Slaughter Slab Survey for Extra-Intestinal Porcine Helminth Infections in Northern Tanzania

A survey on extra-intestinal porcine helminths was conducted at three slaughter slabs that receive pigs from Mbulu, a district endemic for porcine cysticercosis in northern Tanzania. Seventy carcases of pigs between 1 and 2 years old were examined between December 1997 and March 1998. The examination involved ante-mortem lingual examination for Taenia solium cysticercosis followed by post-mortem inspection. In addition, a laboratory procedure was performed to determine whether any of these domestic pigs were infected with Trichinella species. Parasites detected were Ascaris suum (44.3%), Echinococcus granulosus (4.3%) and Taenia hydatigena (1.4%). The lack of cases of porcine cysticercosis in this study compared to previous studies suggests that pig traders are conducting their own ante-mortem lingual examinations before purchasing pigs in the rural communities where the parasite is still highly prevalent. It is concluded that improved meat inspection could prove useful in reducing the local population's risk of infection with these parasites. The results of this study have revealed the parasites of agricultral and public health importance in the targeted communities. Further epidemiological investigations are required to better determine parasite prevalence and impact in order to formulate appropriate and cost-effective strategies for control.     

Vaccination against Taenia solium cysticercosis in underfed rustic pigs of México: roles of age, genetic background and antibody response

Vaccination of pigs of mixed genetic make-up, raised as rustically as done in rural Mexico, resulted in effective protection to experimental challenge against Taenia solium cysticercosis. Maximum protection was achieved if pigs were immunized at 70 days of age. There was large variation of viable parasite load within vaccinated pigs and controls, which is suggestive of significant genetic factors influencing susceptibility, besides immunization. Our results strengthen the advisability of pig vaccination for control of T. solium cysticercosis, since it lowers the number of viable cysticerci capable of transforming into tapeworms.     

Serodiagnosis of porcine cysticercosis by enzyme-linked immunosorbent assay (ELISA) using fractionated antigens

The sensitivity and specificity of the enzyme-linked immunosorbent assay (ELISA) for the diagnosis of Taenia solium cysticercosis was evaluated in experimentally and naturally infected pigs, using T. solium larval scoleces and its fractionated 1st and 2nd peaks on Sephadex G-200 as antigens. First peak antigen gave maximum sensitivity and highest antibody titres. The overall sensitivity of this test was found to be 91.5, 95.8 and 70.8% with scolex, 1st and 2nd peak antigens, respectively. False positive reactions occurred in 9.09% of uninfected pigs with scolex and 1st peak antigens and cross-reactions occurred in 25% of Taenia hydatigena-infected animals using scolex and 2nd peak antigens. No cross-reaction was observed using 1st peak antigen. The specificity of the test was 92.3, 96.2 and 92.3% with scolex, 1st and 2nd peak antigens, respectively.     

A pilot study of common health problems in smallholder pigs in Angónia and Boane districts, Mozambique

A pilot survey was conducted in 2 districts in Mozambique to determine the most important health problems facing smallholder pig producers. While African swine fever is the most serious disease that affects pigs at all levels of production in Mozambique, it is likely that productivity is reduced by the presence of mange and gastrointestinal parasites, while in traditional systems the conditions are favourable for the development of porcine cysticercosis caused by the pork tapeworm Taenia solium, which poses a health risk to communities. Results of the pilot survey confirmed that, with the exception of African swine fever, ecto- and endoparasites are probably the most important health risks for producers. Porcine cysticercosis is more prevalent among pigs in traditional, free-ranging systems, while mange becomes a serious factor when pigs are permanently confined.     

Detection of Taenia solium Cysticercosis in Pigs by ELISA with an Excretory-Secretory Antigen

Serodiagnosis of Taenia solium cysticercosis in pigs was conducted by an enzyme-linked immunosorbent assay with an excretory-secretory antigen. The antigen was obtained by in vitro cultivation of the cysticerci in a synthetic medium RPMI 1640. The sensitivity and specificity of the ELISA in detecting infection in pigs reared on free range was 92% and 100%, respectively. In addition, 33.33% of pigs in which infection could not be detected at meat inspection were found positive by ELISA. However, none of the sera from a group of farm-reared pigs were positive. No cross reactions were observed in pigs that contained either the cysticerci of Taenia hydatigena or hydatid cysts.     

Prevalence of Taenia solium porcine cysticercosis in the Eastern, Southern and Western provinces of Zambia

Tongue examination and detection of circulating antigen (Ag-ELISA) were used to establish the prevalence of Taenia solium porcine cysticercosis in free-range pigs in selected districts of Eastern, Southern and Western provinces of Zambia, and to determine if prevalence of porcine cysticercosis was associated with age, breed and sex. Households with pigs were identified using the snowballing technique. A total of 1691 pigs were examined out of which 183 (10.8%) were positive on tongue examination. Ag-ELISA gave a sero-prevalence of 23.3%. When considering the factors in a logistic regression analysis, only breed type was significantly associated with porcine cysticercosis (OR=0.72; 95%CI=0.63-0.81). The crossbred pigs were 72% more likely to have had cysticercosis than the Nsenga (dwarf local) breed as determined by Ag-ELISA. The result that crossbred pigs had a higher prevalence of T. solium cysticercosis suggests that pig breeds may display different susceptibility to cysticercosis. The limited use of latrines in these areas implies that people use the nearby bush for defecation, resulting in pigs having access to human faeces. Therefore, investigation of taeniosis and cysticercosis in humans is warranted to better comprehend the local epidemiology and transmission risks. This should then be followed by extension programs to communities so that the control plans that could be instituted are more sustainable.     

Taenia solium oncosphere antigens induce immunity in pigs against experimental cysticercosis

Immunity to Taenia solium infection was investigated using an experimental intramuscular oncosphere infection assay (IMOA) model in pigs. Three naturally infected pigs with cysticercosis were treated with oxfendazole (OFZ), a drug demonstrated to kill cysts in porcine muscle. These animals were then challenged with oncospheres but did not develop any cysts while three uninfected pigs that were similarly challenged, did develop intramuscular cysts. In another study, two groups of three pigs each were immunized with crude T. solium oncosphere and metacestode antigens, respectively, and tested with the IMOA. Immunization with crude oncosphere antigens (OAs) induced 100% protection, while metacestode antigens provided only partial protection. Immunoblots showed that pigs with complete immune protection to oncosphere intramuscular challenge had antibodies to two OAs at 31.3 and 22.5 kDa, respectively. Antibody to these two antigens was absent in pigs immunized with metacestodes or in uninfected control pigs. This study demonstrated the presence of two antigens that are unique to the oncosphere. Although, antibody to these two antigens is consistently present in pigs that are protected from an oncosphere intramuscular challenge their role in preventing infection by T. solium larval cysts is still hypothetical.     

Efficacy of the immunoblot assay for cysticercosis in pigs and modulated expression of distinct IgM/IgG activities to Taenia solium antigens in experimental infections

A recently invented immunoblot assay for human cysticercosis was evaluated for efficacy in pigs. The test population consists of 45 pigs with parasitologically confirmed cysticercosis, 47 with heterologous infections, 45 SPF or concrete raised control animals. With this group of 137 animals the test performance was 100% sensitive and 100% specific. The antigen-specific responses of immunoglobulin A (IgA), IgG and IgM in four pigs infected with Taenia solium eggs derived from a human were quantified by immunoblot. Antigen-specific activities were observed as early as 1 week postinfection. The first antigen-specific isotypic response was IgM antibodies directed against a glycoprotein at 97 KD (GP97). This activity generally disappeared between the sixth and ninth week postinfection. Between Weeks 5 and 8, IgG activity rose as IgM activity fell. The IgG activity, however, was directed mostly towards GP50 and GP42 antigens. If the same response occurs in people with cysticercosis, identifying specific isotype activity may help to distinguish new infection from old.     

Epidemiologic observations on porcine cysticercosis in a rural community of Michoacan State, Mexico.

The prevalence of and risk factors for Taenia solium infection (cysticercosis) in pigs were studied in a rural community in Michoacan State, Mexico. Visual inspection of the tongues of 216 pigs revealed cysticerci in 14 (6.5%). The prevalence was slightly higher in male (10/105) than female pigs (4/110) (P = 0.06) and increased with age (P less than 0.05). The most important risk factors for infection in pigs were access to human feces at a public washing area (P = 0.004), the presence of an indoor latrine (P = 0.05) and indiscriminate disposal of human feces around the pig owner's household (P less than 0.1). Effective and long-lasting control of the transmission of T. solium from humans to pigs must include measures to deny pigs access to human feces, a change which is likely to be resisted because of the traditional and functional aspects of established pig-rearing practices.     

Evaluation of tongue inspection and serology for diagnosis of Taenia solium cysticercosis in swine: usefulness of ELISA using purified glycoproteins and recombinant antigen

Evaluation of serology using glycoproteins (GPs) purified by preparative isoelectric focusing (pH 8.8) and recombinant chimeric antigen (RecTs) of Taenia solium was carried out using (1) blood samples on filter papers from pigs infected with different doses of eggs of T. solium in Mexico, (2) serum samples from pigs found infected naturally in Vietnam and Ecuador and (3) serum samples from pigs suspected to be infected with T. solium by tongue inspection in Tanzania. Antibody responses (IgG) were detectable in experimentally infected pigs confirmed harbouring 16 or more cysts at necropsy from 30 days after egg inoculation. One of three pigs naturally infected and harbouring 2.5 cysts/kg muscle and most of pigs harbouring=5.0 cysts/kg were also seropositive by ELISA. Although pigs may be infected with other taeniid species such as Taenia hydatigena, pigs harbouring this parasite were negative in ELISA. Approximately, 76 and 78% of sera from pigs having nodule(s) in the tongue (positive tongue inspection) were serologically positive by both ELISA and immunoblot, respectively. Furthermore, approximately 34 and 18% of sera from pigs having no nodules in the tongue (negative tongue inspection) were also seropositive by ELISA and immunoblot, respectively. ELISA using the two antigens was more sensitive than immunoblot and reliable for differentiation of pigs infected with cysticerci of T. solium from those either uninfected or infected with other taeniid species. Pigs without nodule by tongue inspection should be checked serologically in endemic areas.     

The use of urban sewage sludge on pastures: the cysticercosis threat

Urban sewage production is increasing and its agronomical use as a fertiliser has been advocated. Considerable defiance is prevalent in consumers and among farmers on the use of such fertilisers due to unknown pathological or environmental risks. The aim of the present review was to consider which pathological risk is major. Cysticercosis due to Taenia saginata appears to be one of the major pathological threats when sewage sludge is used to fertilise cattle pastures in temperate areas. The situation is different in Africa (Taenia solium and T. saginata are both highly prevalent) and Asia (Taeniasaginata-like are prevalent). The processing of sludge and the delay between its application onto a pasture and grazing are probably major risk factors. Little data are available on the influence of processing, delay between processing and the use of sludge on the pathogenic risk. Producers and consumers will be more confident on the use of sludge if objective data are gained on risk. Most of the cases of cysticercosis (North America, United-Kingdom, Germany or Denmark) are related to poor human hygiene or accidental overflooding of sewage plants onto pastures. The standard application of sludge on pastures is apparently at low risk. This low risk does not mean that surveillance should cease since outbreaks of cysticercosis have been reported. Future investigations should concentrate on the most sustainable means of reducing risk (length of storage before use, composting, other treatments).     

复方吡喹酮、吡喹酮及丙硫咪唑治疗猪囊虫病的对比试验

应用复方吡喹酮、吡喹酮及丙硫咪唑治疗人工感染囊虫病猪33头,于治疗后4h、24h、77d及100d扑杀,对病猪肌肉组织、脑组织及囊虫进行了病理组织学和超微结构观察。结果表明,三种药物对病猪体内囊虫均具有杀死作用。治疗后24h,复方吡喹酮组病猪体内囊虫全部死亡,而吡喹酮组及丙硫咪唑组病猪体内仍有囊虫存活,治疗后77d及1O0d,复方吡喹酮组病猪体内囊虫全部死亡并被吸收;吡喹酮组病猪体内有多量失去生物活力的囊虫残留;内硫咪唑组病猪体内仍有多量囊虫存活。本实验证实,复方吡喹酮治疗猪囊虫病比吡喹酮及丙硫咪唑的治疗效果迅速而彻底.     

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.