No abstract

Resumen: Los hallazgos más recientes en cuanto a la trasmisión del Toxoplasma gondii en Costa Rica nos indican que la ingestión de carne poco cocida, así como de algunos embutidos, en donde se ha encontrado el parásito en forma viable, son mecanismos de infección importante. Estos aspectos han hecho variar un poco la concepción anterior de que la ingestión de ooquistes del parásito era la principal, sino la única, vía de infección en nuestro país. Por ello se propone un nuevo ciclo de trasmisión para este parásito, comparándolo con el previamente establecido. Este nuevo patrón epidemiológico establece mayores posibilidades de infección con este parásito para los costarricenses.

White rats were inoculated with 10 6 trypomastigotes of Trypanosoma lewisi, simultaneously or two days before and after inoculation with 10 5 oocysts of T. gondií. A greater number of cysts was found in the brain of the animals having concomitant inoculations, as compared with rats inoculated with either one of the two parasites. An apparent immunosuppressive effec! is Iikely. Since both orgartisms can be found in rats, ít is possible that infections with T. lewisi, could make this rodent another intermediate host for Toxoplasma infections

Natural concentration of antimalaric components in Tropical arthropods (in vitro). Alcohol, hexane and dichlorometane extracts of 751 samples of Costa Rican arthropods were studied for the presence of antimalaric components. With Plasmodium berghei we set an in vitro model in which the effect of the extract was determined by staining of the parasites with cresil brilliant blue. Active extracts at concentration of 50 mg or less, were considered positive. Promissory extracts were found in the orders Lepidoptera (24.1%), Coleoptera (32.8%), Hemiptera (38.5%) and Polydesmida (81.3%). Since most of the Lepidoptera samples were in the immature stages, the relation with the host plant was analyzed. Cannaceae, Flacourtiaceae, Crisobalanaceae, Lauraceae, Fagaceae, Ulmaceae, Rosaceae, Asteraceae, Rubiaceae, Lauraceae and Caprifoliaceae were related with the Lepidoptera larvae, and an antimalaric effect has been reported in most of these families. In the orders Polydesmida, Opiliones and Blattodea, the extract from adults also had some important effect, probably because all of them fed on plants. Polydesmida and Opiliones have chemical substances that probably serve as defensive purposes; these chemicals could also have some antiparasitic effect. Therefore, the detection of antimalaric components in arthropod species led to the identification of plants with promissory antimalaric components. Rev. Biol. Trop. 56 (2): 473-485. Epub 2008 June 30.