Elimination of visceral leishmaniasis in Nepal: pipe-dreams and possibilities

Visceral Leishmaniasis (VL) re-emerged in the Indian subcontinent in the mid-1970s after an almost complete absence in the previous fifteen or so years. The disease was first noted in Nepal in 1978 and, since 1980, it has been reported regularly in increasing numbers. Elimination of visceral leishmaniasis by 2015 has been identified as regional priority program in the level of high political commitment.

The objectives of this study are the comprehensive assessment of information related to VL on the basis of past research studies conducted in Nepal, and an assessment of the prospects of control measures.

This was time line comprehensive VL epidemiological assessment study based on the research conducted by main author during the past ten years. During the period the studies were conducted using cross sectional, case control and exploratory study design. The statistical analysis was done using qualitative and quantitative methods.

In our study in the visceral leishmaniasis endemic district, Siraha, in the population of 112,029, a total of 996 clinically suspected cases were reported (with fever of long duration and splenomegaly, with no malaria) during 1998-2002. In all, 283 subjects were found positive for visceral leishmaniasis by rK39 and 284 had positive bone marrow. There was no detectable difference in the density of Phlebotomus argentipes between high, and moderate incidence village development committees (VDC: the smallest administrative unit), but collections in the low incidence areas (in winter) were negative. P. argentipes was never numerous (maximum 4.4 females collected per man-hour), and was much less common than P. papatasi. Peaks of abundance were recorded in the March and September collections. We have found that the numbers of reported cases of visceral leishmaniasis in Nepalese villages was unaffected by indoor residual spray (IRS) indicated by parallel trends in case numbers by time series analysis in treated and untreated villages. A series of maps through ten years clearly showed that the infection can move rapidly between villages, and it is impossible to predict where transmission will occur from year to year.

If maximum benefit in relation to cost is the goal, it may be preferable to put all possible efforts into active case detection (ACD) with free treatment. ACD should involve the network of Village Health Workers or Female Community Health Volunteers and the rK39 dipstick test at health centre level. Surveillance of disease and vector, communication for behavioural impacts and insecticide spraying should be important component of elimination program. If IRS is to be a part of the intervention, it is essential that it is carried out effectively, both in areas where the disease has been reported and in neighbouring areas. Integrated vector management need to be monitored for its application and effectiveness for VL elimination.