Attempts to improve xenodiagnosis: comparative test of sensibility using Rhodnius neglectus, Panstrongylus megistus, Triatoma vitticeps and Triatoma infestans in endemic areas of Brazil.

From June 1984 to July 1992, 392 xenodiagnostic tests were applied on 264 patients with chronic Chagas disease from Brazilian endemic areas of Virgem da Lapa and Coronel Murta, situated in the Jequitinhonha Valley, in the State of Minas Gerais. The susceptibilities of Rhodnius neglectus, Panstrongylus megistus, Triatoma vitticeps and Triatoma infestans were compared. Most of the time 20 nymphs (fourth instar) of each species were applied to 161 women and 103 men aged between 5 and 83 years of age. The tests were prepared to compare the susceptibilities of two species at a time, using the same patients for each test. Results showed a xenopositiveness of 26.28% (103 tests) being 27.98% in women (68 positive in 243 applied tests) and 23.49% in men (35 positive in 149 applied tests). The relative frequency of xenopositiveness displayed a great superiority of P. megistus and T. vitticeps. In tests from type 1, for example, P. megistus was the unique responsible for 10.73% of positive xenodiagnosis vs only 0.98% in T. infestans. Other parameters analized in this work confirm this superiority, and corroborate that T. infestans can be replaced by P. megistus and/or T. vitticeps in order to upgrade the efficacy of xenodiagnosis.