Parasite persistence in treated chagasic patients revealed by xenodiagnosis and polymerase chain reaction

Polymerase chain reaction (PCR) was compared with xenodiagnosis performed 2 0 years after trypanocidal chemotherapy to investigate parasite clearance. Eighty-five seropositive individuals for Chagas disease presenting a positi ve xenodiagnosis were treated with specific drugs; 37 in the acute phase an d 48 in the chronic phase. Fifteen chronic assymptomatic patients received a placebo. Treatment in the acute phase led to FCR negative results in 73% of the cases, while xenodiagnosis was negative in 86%. In the chronic phase , PCR was negative in 65% of the patients and 83% led to xenodiagnosis nega tive results. Regarding the untreated group (placebo), 73% gave negative re sults by xenodiagnosis, of which 36% were positive by PCR. Individuals that were considered seronegative (n=10), presented unequivocally negative resu lts in the PCR demonstrating the elimination of parasite DNA. Seventeen ind ividuals had their antibodies titers decreased to such a level that the fin al results were considered as doubtful and 16 of them presented negative PC R. The molecular method represents a clear advantage over conventional tech niques to demonstrate persistent infections in Chagas disease patients that underwent chemotherapy.