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

RESUMO

Polymerase chain reaction (PCR) was compared with xenodiagnosis performed 20 years after trypanocidal chemotherapy to investigate parasite clearance. Eighty-five seropositive individuals for Chagas disease presenting a positive xenodiagnosis were treated with specific drugs; 37 in the acute phase and 48 in the chronic phase. Fifteen chronic assymptomatic patients received a placebo. Treatment in the acute phase led to PCR negative results in 73 percent of the cases, while xenodiagnosis was negative in 86 percent. In the chronic phase, PCR was negative in 65 percent of the patients and 83 percent led to xenodiagnosis negative results. Regarding the untreated group (placebo), 73 percent gave negative results by xenodiagnosis, of which 36 percent were positive by PCR. Individuals that were considered seronegative (n=10), presented unequivocally negative results in the PCR demonstrating the elimination of parasite DNA. Seventeen individuals had their antibodies titers decreased to such a level that the final results were considered as doubtful and 16 of them presented negative PCR. The molecular method represents a clear advantage over conventional techniques to demonstrate persistent infections in Chagas disease patients that underwent chemotherapy