Visceral leishmaniasis
Visceral leishmaniasis (VL) is the most severe form of leishmaniasis. The disease is fatal if left untreated. The diagnosis of human VL is difficult. The principal signs of VL are an enlarged spleen and a prolonged irregular fever; other signs and symptoms are loss of weight, pallor, enlarged liver, enlarged lymph nodes, anaemia, cough and diarrhoea. These signs and symptoms may mimic those of malaria, typhoid, tuberculosis, schistosomiasis and a number of other diseases. The clinical suspicion may be confirmed directly by the detection of parasites in patient material or by culture. However, sample collection is inconvenient for the patient and parasite isolation by culture is time-consuming, expensive and difficult. Because of the mentioned limitations of the direct diagnostic methods, a number of indirect immunological methods, such as indirect immunofluorescent-antibody tests (IFAT), enzyme-linked immunosorbent assays (ELISA) and a direct agglutination test (DAT), have been developed .

Cutaneous leishmaniasis
In the case of cutaneous leishmaniasis (CL), a systemic serum response is often absent, rendering serology insufficient as a diagnostic tool. Also in the case of HIV co-infection it is often impossible to use a sero-diagnostic test. Detection of the parasite in a skin smear or skin biopsy with microscopy or demonstrating the parasite in culture are in general the standard diagnostic procedures for CL. However, even when these assays are combined, they are not sensitive enough to confirm all CL cases. Therefore, a molecular technique (direct detection of parasite specific DNA or RNA) is needed as an additional diagnostic tool. These techniques are not only ideal for the detection of low numbers of parasites, but also for quantification of the parasite load. Finally, treatment choices depend on the correct identification of the infecting parasite. In particular for New World infections, in which some species can cause more damage to the patient than others and have to be treated differently. In this case, molecular techniques are also helpful tools.