A. Plancarte

Epidemiological investigation of Taenia solium taeniasis and cysticercosis in a rural village of Michoacan State, Mexico

We performed a survey for taeniasis and cysticercosis among persons living in a Mexican village where Taenia solium infection in pigs was known to be enzootic. A standardized questionnaire was administered in all 577 households to obtain medical histories and information on demographic and environmental factors and on risk factors associated with transmission of infection. Serum and/or stool specimens were obtained from 1005 volunteers and examined for cysticercosis antibodies and intestinal parasites. Faecal examination of 828 participants revealed infection by Taenia sp. in 2 (0.2%). Three additional cases of taeniasis were detected in individuals who evacuated proglottids after treatment with praziquantel. Of 1005 human serum specimens, 49 (4.9%) were positive in the cysticercosis immunoblot assay. Seropositivity increased with age and reached a peak in subjects aged 46-55 years (P < 0.05). A history of seizures was significantly associated with seropositivity (P < 0.05); approximately 25% of persons with such histories were seropositive. Histories of headache, dizziness, trembling, blurred vision, and vomiting were also significantly associated with positive immunoblot assays. This study has demonstrated previously undiagnosed morbidity associated with T. solium neurocysticercosis and identified community behavioural and environmental practices that must be modified to prevent continued transmission of cysticercosis and taeniasis.

Vaccination against Taenia solium cysticercosis in pigs using native and recombinant oncosphere antigens

Pigs were immunised with antigens derived from Taenia solium oncospheres or with a pool of three recombinant antigens from Taenia ovis, and subsequently challenged with T. solium eggs. The native oncosphere antigens induced 83% protection against viable, and 89% protection against the total number of cysticerci established following the challenge infection. Immunisation with the recombinant T. ovis antigens induced 93% protection against the establishment of viable cysticerci, and 74% protection against the total number of cysticerci. These results, and those achieved elsewhere with Taenia saginata and T. ovis, support the possibility of developing a practical vaccine to assist in the control of transmission of T. solium through pigs.

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.

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.

Human neurocysticercosis: comparison of enzyme immunoassay capture techniques based on monoclonal and polyclonal antibodies for the detection of parasite products in cerebrospinal fluid

Current diagnosis of neurocysticercosis relies mostly on computerized tomography and nuclear magnetic resonance, with detection of antibodies being confirmatory rather than decisive. An assay which detects parasite products in cerebrospinal fluid would conclusively demonstrate a current infection and could be important when decisions regarding treatment must be made. Cerebrospinal fluid from patients with neurocysticercosis was used in 4 enzyme immunoassay capture tests designed to detect parasite products. Of the systems tested, one, based on the use of a monoclonal antibody reactive with a surface and secretion component of the metacestode, was particularly promising, giving a sensitivity of 72%. The assay has the double advantage of a very low background and a proved specificity for the products of living cysticerci. The other 3 systems (monoclonal anti-vesicular fluid antibody, polyclonal antibody against a saline extract and polyclonal anti-antigen B antibody) were less sensitive. Results with the anti-antigen B system support the proposal that products of low immunogenicity are the most appropriate targets for the serological detection of the parasite.

Experimental Taenia solium cysticercosis in pigs: characteristics of the infection and antibody response.

Pigs were infected with taeniid eggs to study the susceptibility to infection and reinfection of the animals of mixed breeds and of different ages, the viability and death of the metacestodes in the host tissue, and the antibody response which accompanies these events. Sixteen pigs were infected with Taenia solium eggs for this purpose. At necropsy metacestodes were counted in 2 kg of shoulder muscles and classified as vesicular or caseous, and all the metacestodes in brains were counted and classified. The results show that pigs inoculated at 49 and 60 days of age became infected to different degrees and reacted differently to the presence of parasites. In the brain the metacestodes remain viable for longer periods than in muscles. Enzyme-linked immunosorbent assay (ELISA) showed a significant rise in antibodies after infection, which started to decrease 92 days post-infection (p.i.). Pigs with viable cysts remained seropositive up to the end of the experiment (281 days p.i.). Antibody levels rose further after reinfection or after treatment. The results of Western blot were comparable to those of ELISA. Antigens of 13, 14 and 18 kDa were most frequently recognized in early infections and then started to decrease 92 days p.i., while the antigens of 42, 50 and 24 kDa were recognized during later stages of infection (200 days p.i.). The results suggest that older animals are more resistant to the infection [corrected].

ELISA and immunoblot using purified glycoproteins for serodiagnosis of cysticercosis in pigs naturally infected with Taenia solium.

The establishment of reliable serological methods for cysticercosis in pigs is important for the surveillance, control and prevention of taeniosis/cysticercosis in humans as well as in pigs to prevent economic loss. Both ELISA and immunoblot using glycoproteins (GPs) purified by a single step of preparative iso-electric focusing, which are highly useful for human cysticercosis, have been applied for a serological study in pigs naturally infected with Taenia solium. All sera from pigs showed similar responses to those in human cysticercosis. Therefore, it is expected that both ELISA and immunoblots using GPs would be useful in differentiating infected pigs from uninfected ones.

Host--parasite relationship in cysticercosis: immunologic study in different compartments of the host.

Cysticerci parasitize several mammalian species, including man, in which the parasitic disease shows unique characteristics since cysticerci are established mainly in immunologically privileged sites and can survive for many years. The study of the human immune response to cysticerci is helpful in diagnosis and could perhaps also aid in preventing or curing the disease. Anti-cysticercus IgG can be detected in serum and cerebrospinal fluid (CSF) of almost all patients with neurocysticercosis, by the enzyme-linked immunosorbent assay (ELISA); antibodies of the other classes are found less frequently. Antibodies react with up to eight Taenia solium cysticercus antigens, mainly with antigen B. This antigen has an affinity for collagen and is not commonly found in the CSF. It could therefore be participating in vasculitic processes spotted in the brain of neurocysticercotic patients. Immunoglobulins are also identified on the surface of the parasites: IgG is detected on parasites obtained from various tissues; IgM, IgA and IgE mostly on extracerebral cysticerci. We discuss the possibility of extraneural cysticerci being destroyed by the immune response of the host whereas natural aging may cause brain cysticerci death.

Heterogeneity of humoral immune components in human cysticercosis.

Twelve Taenia solium cysticerci, obtained from several human organs, were examined by immunofluorescence for IgG, IgM, IgA, IgE and C3b on their surfaces. Anti-cysticercus antibodies of the 4 classes of immunoglobulins were looked for in the cerebrospinal fluid of most neurologic patients, in the intraocular humors of a patient with eye cysticercosis, and in the serum of some other patients. The morphological appearance of the parasites as well as the clinical features of the patients were recorded. The distribution of components was heterogeneous among the different parasite surfaces. IgG was the most frequent, followed by IgA, IgM, C3b and IgE. No correlation was found between the presence of these molecules and signs of damage in the cysticerci, or with the classes of immunoglobulins found as anti-cysticercus antibodies. Possible explanations of these findings as well as the implications of heterogeneity in cysticercosis are discussed.

THE EXPERIMENTAL INFECTION OF PIGS WITH DIFFERENT NUMBERS OF TAENIA SOLIUM EGGS: IMMUNE RESPONSE AND EFFICIENCY OF ESTABLISHMENT

Three of 4 pigs inoculated with 10 eggs of Taenia solium became infected. In those pigs infected with larger numbers of eggs, all became infected. Specific antibodies against the metacestodes were found in serum at day 30 postinoculation (PI) in animals that received 1,000 or more eggs and at day 60 in those that received 10 or 100 eggs. The concentration and diversity of antibodies increased up to the day of death in pigs that received 10,000 or 100,000 eggs. All pigs infected with 1,000 or more eggs developed antibodies, but only 40% and 75% of pigs that received 10 and 100 eggs, respectively, developed antibodies. Metacestodes were found in the muscles of 23 of the 27 infected animals. In 35.7% of the pigs that received 1,000 or more eggs, metacestodes were also found in the brain. Most of the metacestodes found in pigs infected with 10 or 100 eggs were caseous, whereas in pigs infected with 1,000 or more eggs the majority of metacestodes were vesicular. This study shows that the severity of T. solium infection and the possible regulation of the immune system–evasion mechanisms depend on the number of metacestodes that succeed in establishing themselves and remain vesicular.