Cell cloning techniques and schizodeme analysis were used to detect mixtures of subpopulations in Leishmania parasites, isolated from humans and a reservoir host. Clones were obtained by plating promastigotes, at limited dilution, on solid medium. The resultant colonies were analysed by the restriction profile of kinetoplast DNA minicircles (schizodeme analysis). The efficiency of plating was around 40–60%, and subpopulations of different schizodemes, in stocks of Leishmania isolated from 2 cases of human cutaneous leishmaniasis were detected. The presence of different schizodemes in one isolate from a sylvatic animal suggested the possibility of a mixed natural infection.

Neuronal lesions have been considered the hallmark of chagasic megaesophagus, but the role of Trypanosoma cruzi and the participation of the inflammatory cells in this process are still debated. In the present study we counted neurons in the oesophagus from patients with and without megaesophagus and further examined these samples for the presence of parasite kDNA and cells with cytolytic potential (Natural Killer cells, cytotoxic lymphocytes and macrophages). The presence of parasite kDNA was demonstrated in 100% of cases with megaesophagus and in 60% of patients without megaesophagus. When analysed for the number of neurons, the patients without megaesophagus could be classified into 2 groups, as having normal or a decreased number of neurons. The former group did not show any inflammatory process, but interestingly, all patients without megaesophagus presenting decreased number of neurons also presented both parasite kDNA and inflammatory process in the organ. We further observed that the numbers of cytotoxic cells in the myenteric plexus region inversely correlate with the number of neurons. These data together strongly suggest that chronic lesions in chagasic megaesophagus might be a consequence of immune-mediated mechanisms, that last until the chronic phase of infection, and are dependent on the persistence of parasite in the host's tissue.