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A series of already published and unpublished seroepidemiological surveys for toxoplasmosis, carried out in Chile in 1982-1994, is reviewed, expanded and analyzed. The surveys included 76,317 apparently healthy individuals of different ages (0.57% of the country's total population), from 309 urban and rural-periurban localities. Urban groups were integrated by blood donors, delivering mothers and middle grade schoolchildren, while rural-periurban individuals corresponded to unselected family groups. Blood samples were collected in filter paper. The presence of antibodies to Toxoplasma gondii was determined by the indirect hemagglutination test (IHAT), titers > or = 16 were considered positive. The test resulted positive in 28,124 (36.9%) of the surveyed people. Two hundred and six (0.3%) individuals presented IHAT titers > or = 1000, probably corresponding to acute or reactivated infections. A progressive increase of positive IHAT from northern to southern regions of the country was noted, phenomenon probably related to geographical conditions and to a higher production and consumption of different types of meat in the latter regions. It is postulated that ingestion of T gondii cysts by humans is epidemiologically as important as ingestion of oocysts. The result presented stress the epidemiological importance of toxoplasmosis in humans, and warn about eventual implications in immunocompromised patients and in transplacental transmission, organ transplants and transfusions.

The simultaneous application of more than one technique for the parasitological diagnosis of Chagas' disease in untreated individuals increases the possibility of detection of T. cruzi.

In the xenodiagnosis (XD) of American trypanosomiasis (Chagas disease), Trypanosoma cruzi in the triatomine bugs fed on the patient can now be detected using PCR (XD-PCR) as well as by microscopy (XD-M). In a study to compare XD-PCR with XD-M, triatomine bugs were fed on 50 cases of chronic American trypanosomiasis, of whom only 25 were ever found positive by XD-M. Overall, the bugs fed on 34 of the patients (all 25 cases found positive by XD-M and nine of the other patients) were found PCR-positive, giving a 330-bp fragment corresponding to part of the hyper variable region of the kinetoplast DNA of T. cruzi. Of the 25 patients who were ever found positive by XD-M, 20 gave bugs that were smear-positive on day 90 and a similar number (24; P=0.125) gave bugs that were PCR-positive at this time. On day 30, however, the bugs fed on only 11 of these 25 patients were found positive by microscopy, whereas 23 of these patients were found positive by XD-PCR (P=0.0016). Thus, not only was XD-PCR more sensitive than XD-M but it was also quicker, revealing more cases within 30 days than detected using XD-M over a period of 90 days.