The existence of patients suffering a double
infection caused by Trypanosoma cruzi and Leishmania spp. has been suggested by several authors. Since the conventional serological tests now available for the diagnosis of
Chagas' disease lack specificity due to the cross-reactivity between these two parasites, a serological confirmation of a T. cruzi
infection cannot be made unless specific
antigens are used. An
enzyme linked
immunosorbent assay (ELISA) to detect
antibodies against a specific T. cruzi
antigen, named Ag163B6, and immunoblotting using T. cruzi epimastigotes, are non-conventional serological techniques that could be employed for specific diagnosis of
Chagas' disease. Using these two methods 34 cutaneous or
mucocutaneous leishmaniasis patients were classified into two groups: (A) patients with serological evidence of T. cruzi
infection, i.e. those who tested positive in at least one assay (18/34); and (B) patients with no serological evidence of T. cruzi
infection, i.e. those who were negative for both assays (16/34). Taking into account the difficulties of xenodiagnosis and its low sensitivity (less than 50%) for a direct diagnosis in the chronic period of the disease, we used polymerase chain reaction (PCR) to confirm a T. cruzi
infection in those
leishmaniasis patients who presented positive results with the non-conventional serological techniques. Of the 18 patients with serological evidence of T. cruzi
infection, 17 gave positive results when genomic
DNA primers were used. Using minicircle primers, 15/18 of that group were positive. Nevertheless, all the patients suspected of being double infected were positive in at least one PCR test. Just one patient with no serological evidence of T. cruzi
infection gave a positive PCR result when amplifying the minicircle sequence. The proof of the existence of a T. cruzi
infection by PCR in
leishmaniasis patients suspected to be chagasic when non-conventional serology was used, strongly supports the use of the specific Ag163B6 and immunoblotting with epimastigotes as specific serological diagnostic tools to determine a T. cruzi
infection.