Infantile Mediterranean visceral leishmaniasis (IVL) and anthroponotic cutaneous leishmaniasis (ACL) have long been known to exist in the western and southeastern Turkey, respectively. To further study these and other related diseases, a recombinant antigen (rK39) specific to VL was used in an ELISA for serodiagnosis of selected patients and for screening dog reservoir populations in several endemic sites. Among 24 confirmed VL cases from western Turkey, the rK39 ELISA proved to be more sensitive than a combination of cultivation and microscopy of bone marrow aspirates. The specificity of rK39 for leishmaniasis was demonstrated by its lack of cross-reactivity with sera from other human diseases in the same sites. Interestingly, six of the 83 parasitologically proven ACL cases from southeast Turkey were also rK39 positive. The end point titers of the positive VL and CL cases vary from 10(-2) to 10(-5) and from 10(-2) to 10(-3), respectively. The rK39 ELISA was also used to screen 494 apparently healthy dogs from Urfa in southeast Turkey, Manisa/Alasehir near the Aegean Sea, and Karabuk near the Black Sea. Eighteen rK39-positive cases (3.6%), all from the latter two areas, were found to have varying endpoint titers (10(-2)-10(-4)). The high titers predicted increased severity and frequency of the clinical symptoms (i.e., lymphadenopathy, depilation, skin lesion, weight loss and/or death), which were manifested subsequently in 16 of these 18 cases. In addition, more positive canine cases were diagnosed by the rK39 ELISA preclinically than the procedures to detect parasites postsymptomatically in the lymph node aspirates. The use of the rK39 ELISA as a sensitive tool makes it possible to demonstrate coendemicity of canine and human VL, as expected in the case of IVL. The results also point to the possible presence of additional VL types in western Turkey and cutanovisceral type in the southeast part of this country.