Chinchilla laniger can be used as an experimental model for Taenia solium taeniasis.

Chinchilla laniger has been reported as an experimental definitive host for Taenia solium; however no information about its suitability and yield of gravid tapeworm proglottids containing viable and infective eggs has been published. In total 55 outbred female chinchillas were infected with 4 cysticerci each; hosts were immunodeppressed with 6 or 8 mg of methyl-prednisolone acetate every 14 days starting the day of infection and their discomfort was followed. Kinetics of coproantigen ELISA or expelled proglottids was used to define the infection status. Efficiency of tapeworm establishment was 21% and of parasite gravidity was 8%; chinchillas showed some degree of suffering along the infection. Viability of eggs obtained from gravid proglottids was tested comparing methods previously published, our results showed 62% viability with propidium iodide, 54% with trypan blue, 34% with neutral red, 30% by oncosphere activation and 7% with bromide 3-(4,5-dimetil-tiazol-2-il)-2,5-difenil-tetrazolio (MTT) reduction; no statistical differences were obtained between most techniques, except activation. Four piglets were infected with 50,000 eggs each, necropsy was performed 3 months later and, after counting the number of cysticerci recovered, the percentage of infection was similar to data obtained with T. solium eggs recovered from humans. Our results demonstrate that the experimental model of T. solium taeniasis in C. laniger is a good alternative for providing eggs and adult tapeworms to be used in different types of experiments; optimization of the model probably depends on the use of inbred hosts and on the reduction of infected animals' suffering.

Development of Taenia pisiformis in golden hamster (Mesocricetus auratus).

The life cycle of Taenia pisiformis includes canines as definitive hosts and rabbits as intermediate hosts. Golden hamster (Mesocricetus auratus) is a rodent that has been successfully used as experimental model of Taenia solium taeniosis. In the present study we describe the course of T. pisiformis infection in experimentally infected golden hamsters. Ten females, treated with methyl-prednisolone acetate were infected with three T. pisiformis cysticerci each one excised from one rabbit. Proglottids released in faeces and adults recovered during necropsy showed that all animals were infected. Eggs obtained from the hamsters' tapeworms, were assessed for viability using trypan blue or propidium iodide stains. Afterwards, some rabbits were inoculated with eggs, necropsy was performed after seven weeks and viable cysticerci were obtained. Our results demonstrate that the experimental model of adult Taenia pisiformis in golden hamster can replace the use of canines in order to study this parasite and to provide eggs and adult tapeworms to be used in different types of experiments.

Standardization of an experimental model of human taeniosis for oral vaccination.

Neurocysticercosis in humans is caused by the tapeworm Taenia solium and generates substantial morbidity in Latin America, Africa and Asia.The life cycle of T. solium includes pigs as intermediate hosts and human beings as definitive hosts. Tapeworm carriers are the main risk factor for acquiring cysticercosis in the household, thus prevention and control programs are being developed. Infected people have no symptoms, therefore are difficult to identify and treat, thus vaccination against the adult tapeworm is an alternative control measure. Since the infection occurs naturally only in human beings, experimental models have been standardized. Hamsters are believed to be good models to study the infection but they have not been properly evaluated for vaccination. Since taeniosis is gained by ingesting pork meat with cysticerci, oral vaccination was evaluated, and given that intestinal immunity is enhanced with adjuvants, cholera toxin was used, because it is one of the most potent adjuvants, in view of the fact that it increases epithelium permeability enhancing entrance of the co-administered unrelated antigens. Recombinant functional T. solium calreticulin was employed for the standardization of the methodology and the evaluation of oral vaccination. Protection was associated with the type of cysticerci and the age of the hamsters used. When reddish bigger parasites were orally introduced in hamsters as challenge, protection was around 40%, while when yellowish small parasites were used, protection increased to 100%, suggesting that the characteristics of cysticerci are determinant. Protection was gained in 9month old hamsters, but not in 3month old animals.

[Taeniasis and detection of antibodies against cysticercus among inhabitants of a rural community in Guerrero State, Mexico]. / Teniosis y detección de anticuerpos anticisticerco en personas de una comunidad rural del estado de Guerrero.

OBJECTIVE: To assess the frequency of Taenia solium carriers and its relationship with human cysticercosis in a Mexican locality. MATERIAL AND METHODS: A cross-sectional study was conducted in 1998, in a locality of Guerrero State, Mexico. Four hundred and three fecal samples were analyzed by enzyme-linked immunosorbent assay (ELISA) to detect Taenia sp coproantigen. Ninety two serum samples were also analyzed for antibodies against cisticerci using the immunoelectrotransfer blot assay (IET). Data were analyzed using descriptive statistics and odds ratios. RESULTS: Five of the 403 fecal samples were positive (1.2%). The adult cestode was recovered in only two people. Three (3.26%) out of the 92 serum samples that were analyzed for anticysticercus antibodies were positive. Seventeen serum samples corresponded to people living with a person positive to the coproantigen test (first group), the remaining 75 were obtained from people without a history of releasing taenia proglottids (second group). In the first group, 2 positive sera were detected (11.8%), while in the second only I was positive (1.3%) (odds ratio = 9.87, 95% confidence interval 0.64 to 295.56, p = 0.08). CONCLUSIONS: The difficulty to obtain the adult parasite in persons positive to coproantigens, may be due to difficult expulsion, a shorter permanence of the parasite in the host, insufficient dosage of treatment, or to lack of specificity of the diagnostic test. Further studies are needed to evaluate these possibilities; a better knowledge of parasite transmission dynamics will allow the implementation of prevention and control measures and a better assessment of diagnostic tests under field conditions. The English version of this paper is available at: http://www.insp.mx/salud/index.html.

Teniosis y detección de anticuerpos anticisticerco en personas de una comunidad rural del estado de Guerrero / Taeniosis and detection of antibodies against cysticerci among inhabitants of a rural community in Guerrero State, Mexico

OBJETIVO: Determinar la frecuencia de portadores de Taenia sp. y su relación con el diagnóstico de cisticercos en humanos en una comunidad rural del estado de Guerrero, México. MATERIAL Y MÉTODOS: Para detectar portadores de Taenia sp. se analizaron 403 muestras de heces de personas, por medio de ELISA para coproantígenos de Taenia sp., así como 92 muestras de suero para detectar anticuerpos anticisticerco mediante inmunoelectrotransferencia. El diseño del estudio fue transversal y se llevó a cabo durante 1998. Se hizo estadística descriptiva y se estimó razón de momios. RESULTADOS: De 403 muestras de heces evaluadas, cinco resultaron positivas (1.2 por ciento). Sólo en dos de las cinco personas positivas se obtuvo el cestodo adulto. En 3 (3.26 por ciento) de los 92 sueros se encontraron anticuerpos anticisticerco. Del total de sueros, 17 fueron de las personas con diagnóstico positivo a teniosis por coproantígenos o que cohabitaban con ellos (primer grupo), los restantes 75 provenían de personas en quienes no se detectaron casos en las viviendas (segundo grupo). En el primer grupo se detectaron 2 (11.8 por ciento) sueros positivos, mientras que en el segundo sólo 1 (1.3 por ciento) (RM= 9.87, I.C 0.64-295.56, p= 0.086). CONCLUSIONES: La dificultad para obtener el parásito adulto en las personas positivas a coproantígenos puede deberse a características propias de éste que dificultan su expulsión, a que la permanencia del cestodo en su huésped es menor a la esperada o a que el tratamiento fue insuficiente para obtener el parásito, o bien, a problemas de especificidad de la prueba. Es necesario realizar estudios tendientes a evaluar estas posibilidades, lo cual permitiría conocer mejor la dinámica de transmisión de esta parasitosis, con el fin de establecer medidas de prevención y control, además de poder comparar con mayor veracidad la eficacia de las pruebas diagnósticas en condiciones de campo

Estudio de invidividuos con teniosis y su asociación con enfermos con neurocisticercosis / Association of neurocisticercosis patients with taenia carriers

La cisticercosis es la parasitosis más frecuente del sistema nervioso central. El principal factor de riesgo para adquirir neurocisticercosis (NCC) es la presencia en casa de un portador del estadio adulto de la Taenia solium, quien generalmente es asintomático, aunque se pueden identificar los proglótidos en su materia fecal. Con el propósito de identificar a dichos portadores se estudiaron pacientes con NCC que asistían al Servicio de Neurología del Hospital de Especialidades del Centro Médico Nacional Siglo XXI, así como a sus familias. También se incluyeron en el estudio los casos de teniosis del Instituto Nacional de Pediatría, así como los reportados por los Laboratorios Estatales de Salud Pública del Estado de México y de Tlaxcala. Se analizaron los cuadros clínicos de los enfermos con NCC y con teniosis. Las manifestaciones clínicas de NCC encontradas fueron similares a las descritas en la literatura. En pacientes con teniosis, la cefalea, hiperorexia, dolor en hipocondrio derecho y estreñimiento se presentaron con significancia estadística. Fue notoria la dificultad técnica para el diagnóstico de teniosis y para la obtención del parásito una vez administrado el tratamiento, así como la falta de información sobre la enfermedad, por parte de los pacientes con teniosis y sus familias.