Treatment of Visceral Leishmaniasis (VL), a neglected tropical disease, is very challenging with few treatment options. Long duration of treatment and drug toxicity further limit the target of achieving VL elimination. Chemotherapy remains the treatment of choice. Single dose of liposomal amphotericin B (LAmB) and multidrug therapy (LAmB + miltefosine, LAmB + paromomycin (PM), or miltefosine + PM) are recommended treatment regimen for treatment of VL in Indian sub-continent. Combination therapy of pentavalent antimonials (Sbv) and PM in East Africa and LAmB in the Mediterranean region/South America remains the treatment of choice. Various drugs having anti-leishmania properties are in preclinical phase and need further development. An effective treatment and secondary prophylaxis of HIV-VL co-infection should be developed to decrease treatment failure and drug resistance.

Following sequence analysis of a Leishmania donovani kinetoplast DNA (kDNA) minicircle, we have developed synthetic oligonucleotides for use in the polymerase chain reaction (PCR). With these primers, we have amplified L. donovani kDNA from splenic aspirates and blood samples taken from kala-azar patients. Treatment of the samples for PCR requires only limited DNA purification by lysis in SDS, digestion with proteinase K, phenol extraction and ethanol precipitation of the resulting nucleic acid. We have obtained amplified product routinely with DNA prepared from the equivalent of 2·5–25 µl of splenic aspirate or of 50–500 µl of blood from infected patients. In dilution experiments a visible product has been obtained on amplification of DNA from the equivalent of 2·5 × 10−7 µl of splenic material. We therefore propose the amplification of L. donovani kDNA by PCR as a rapid and highly sensitive method for the diagnosis of kala-azar.

Leishmania donovani causes visceral disease (kala-azar), a major health problem throughout the tropics with 500 000 new cases every year. Leishmania differentiates from the promastigote to the amastigote form to establish infection in a mammalian host. To understand the process of differentiation, we assessed the global variation in gene expression in promastigotes, an intermediate stage of differentiation (PA24) and axenic amastigotes in culture using an L. donovani genomic microarray with 4224 clones printed in triplicate. During an intermediate stage of differentiation 24 h after shifting the promastigotes into amastigotes (PA24), there were 41 (∼1%) clones with expression ⩾2·0-fold higher than promastigotes, whereas in terminally differentiated amastigotes there were 130 (∼3%) such clones. Of particular interest were certain genes that exhibited a transient increase or decrease in expression at the PA24 stage. Kinases showed a transient increase, and surface molecules, PSA and amino acid permease, were prominent clones among those showing a brief decrease at the PA24 stage. The microarray results have been validated using Northern blots or RT-PCR. In summary, our results provide important clues about the genes involved in the differentiation process of L. donovani that may contribute to virulence.

The diagnosis of visceral leishmaniasis must be based upon a demonstration of the parasite in tissues of the patient. The best diagnostic test is a splenic aspirate, which is safe, highly sensitive and specific if the technique described in this paper is used and both smears and cultures of the aspirate are performed. Peripheral blood and nasal exudate have parasites in smears and/or cultures in 75 and 40% of Kenyan visceral leishmaniasis patients, respectively. Sodium stibogluconate (Pentostam) is the preferred treatment for visceral leishmaniasis. Recent Clinical Research Centre trials of different schedules of treatment with sodium stibogluconate are discussed. Currently, we recommend sodium stibogluconate, 20 mg/kg once daily for 30 days, for initial treatment. For patients who have not responded to initial treatment with sodium stibogluconate or have relapsed after initially responding to this treatment, we recommend sodium stibogluconate, 20 mg/kg once daily for 60 days. Further studies are now underway comparing the combination of allopurinol plus sodium stibogluconate versus sodium stibogluconate alone for unresponsive or relapsed patients.

Studies of the epidemiology of visceral leishmaniasis in the West Pokot focus have revealed that Sergentomyia bedfordi, S. antennatus and S. schwetzi are the most abundant sandfly species. The latter have been shown to feed mainly on lizards. Phlebotomus martini was encountered in termite hills in the ventilation shafts, and showed an even distribution among the termite hills throughout the district where kala-azar cases were detected. Investigations into the relationship between termite hills and the presence of kala-azar cases in various homes were carried out. All homes afflicted with kala-azar had a termite hill or hills within a 10-m radius. The period of time spent in own homestead by each kala-azar case was to establish if each kala-azar patient contracted the disease in the focus of investigation.

Wild-caught phlebotomine sandflies were captured from rock crevices and termite hills and released into feeding cages containing various species of laboratory animals, to find suitable hosts for feeding flies for experimental or breeding purposes. Flies captured from rock crevices did not feed as well as those human-baited at termite hills. The ubiquitous species from the termite hills was Phlebotomus martini, the major vector of kala-azar in the study area (Machakos District of Kenya). This anthropophilic species feeds readily on the mammalian laboratory animals. Cooling flies before feeding stimulated them to feed.

Various species of sandflies were collected from outdoor natural resting sites from three districts in Kenya which are endemic for kala-azar (Machakos, West Pokot and Baringo). Their blood-meals were analysed to find out host preferences. Female fed-flies were dissected for parasitological investigation. Lizards from these areas were also trapped and blood and internal organs were examined and cultured for isolation of leishmania parasites. Only the lizards obtained from West Pokot and Baringo revealed leishmania parasites in cultures. Bloodmeal analysis showed that Phlebotomus anten-natus, P. bedfordi, P. schwetzi, P. africanus, P. martini, P. affinis and P. rodhaini fed on reptiles. Additionally, promastigotes were seen and isolated from these sandfly species. The disease incidence appears to be less in areas where leishmania parasites were encountered both in lizards and the sandflies in the same locality.