Haematogenous dissemination of Leishmania (Viannia) braziliensis in human American tegumentary leishmaniasis.

One of the potential dangers of American tegumentary leishmaniasis (ATL) caused by Leishmania (Viannia) braziliensis is the development of mucosal lesions. Haematogenous dissemination of the parasite is the most likely mechanism to explain this occurrence, but most attempts to isolate the parasite from blood have so far been unsuccessful. The presence of Leishmania in peripheral blood was therefore evaluated by PCR using DNA samples isolated from patients presenting active cutaneous or mucosal disease, and from individuals cured by antimonial treatment as well as individuals without a past history of leishmaniasis but with a positive Montenegro skin test, all living in L. (V.) braziliensis-endemic areas. Leishmania DNA was found not only in those patients presenting active cutaneous (24.8%) or mucosal (35%) lesions, but also in samples isolated from healed individuals (27.3%) as well as in asymptomatic skin-test-positive residents of endemic areas (37.5%). Overall, PCR showed the presence of parasite DNA in the blood of 26.2% of the 225 examined samples. These data suggest that persistence of parasites within the host may last for many years and, rather than being a risk factor, might be important in maintaining the protective response in those living in endemic areas.