The positive rapid rK39 immunochromatographic dipstick test in 100% VL and 31.8% LCL patients, and 6.5% dogs suggests that both VL and LCL in this focus are apparently being caused by L. donovani-infantum and that reservoir infection is perhaps being chiefly maintained in asymptomatic dogs. However, it needs corroborative evidence in the form of in-vitro parasite cultivation and/or PCR studies for confirmation. A more elaborate study is recommended.

Background: A mixed endemic focus of cutaneous and visceral leishmaniasis has emerged along the Sutluj river valley of Himachal Pradesh (India). Methods: The laboratory work up of 218 new consecutive cases of localized cutaneous leishmaniasis (LCL) and 14 patients of visceral leishmaniasis (VL) from this focus is analyzed. Results: Tissue smears were positive in 44.42% of LCL and 78.57% of VL patients. Positivity was higher (73.97%) in LCL lesions of <6months duration as compared to (36.53%) those of >6months duration. Only modified NNN medium supplemented with RPMI 1640 and 10% heat inactivated fetal bovine serum was found to be the most suitable for primary isolation of the parasite while other seven media used did not yield significant growth. Culture for the organism was positive in 38 of 112 (33.92%) patients of LCL and 9 of 14 (64.28%) patients of VL. The cultured organisms from 4 each of LCL and VL samples were identified by PCR as Leishmania donovani. Although subculture/bulk cultivation of this Leishmania spp. was unsuccessful in the various media tried, the two of the primary cultures could be maintained for 50 days by just replenishing the liquid overlay. Conclusion: This new focus of leishmaniasis appears peculiar where cutaneous and visceral forms co-exist, and both Leishmania donovani and Leishmania tropica are producing LCL all the while L. donovani being the predominant pathogen. The difficulty in culturing the isolates is also reminiscent of LCL caused by Leishmania infantum suggesting that these isolates, both from LCL and VL patients, perhaps belong to Leishmania donovani-infantum complex.