[Correlation among the positivity of the artificial xenodiagnosis and the amount of blood and triatomines used in the exam, in chronic chagasic patients].

The aim of this study was to verify whether the amount of blood and number of triotomines used could improve the artificial xenodiagnosis performed in 200 chronic phase infected individuals. Ten or 40ml of peripheral blood was collected in heparinized (20.4 IU) vacuum tubes, and fed to 60 and 360 triatomines, respectively. Dipetalogaster maximus (1st instar, about 15 days after eclosion), as well as 3rd instar Triatoma infestans and Triatoma vitticeps and the 4th instar of Rhodnius neglectus were used. The faecal examinations were performed 30 and 60 days after xenodiagnosis procedure. The positivity with 10ml of blood was 19% and with 40ml, 44%, from which it was concluded that a correlation existed between the amount of blood and the number of triatomines used (p < 0.01). The positivity of the xenodiagnosis ranged from 9.7 to 100%, higher in young and adults up to 34 years old, but independent in relation to the sex of the chronic chagasic individuals studied.