Evidence for visceral leishmaniasis elimination in Nepal
Authors: Megha Raj Banjara, Anand Ballabh Joshi
Journal: The Lancet Global Health (2020)

Visceral leishmaniasis is an important public health problem in Nepal. In 2005, Bangladesh, India, and Nepal signed a memorandum of understanding to eliminate visceral leishmaniasis in this region by 2015. As the elimination target was not reached in 2015, the date has been extended to 2020. The visceral leishmaniasis elimination strategy emphasised early case detection, effective treatment, integrated vector management, and reduced transmission. Although Nepal achieved elimination targets in all 12 visceral leishmaniasis endemic districts from 2013 and thereafter, one of the previously non-endemic districts crossed the elimination target in 2017, however, this achieved target is not sustainable. A substantial reduction of visceral leishmaniasis incidence has been observed in the Indian subcontinent and Nepal has reduced its visceral leishmaniasis incidence by 90% compared with 2005.1Department of Health Services, NepalAnnual report 2017/2018.https://dohs.gov.np/annual-report-2074-75/Date accessed: November 26, 2019Google Scholar Despite this progress, the disease has now been reported in new ecological niches and hilly districts of Nepal in which there is no visceral leishmaniasis control programme.2Banjara MR Gurung CK Uranw S Pandey K Internal assessment of kala-azar elimination programme of Nepal. Public Health and Infectious Disease Research Center (PHIDReC), Nepal, Kathmandu, Nepal2015Google Scholar, 3Uranw S Hasker E Roy L et al.An outbreak investigation of visceral leishmaniasis among residents of Dharan town, eastern Nepal, evidence for urban transmission of Leishmania donovani.BMC Infect Dis. 2013; 13: 21Crossref PubMed Scopus (19) Google Scholar With the support of different partners, operational research is being done to generate facts for evidence-based policy to eliminate visceral leishmaniasis. Several randomised drug trials were designed and implemented to support visceral leishmaniasis elimination initiatives. On a related note, with the support of the WHO Special Programme for Research and Training in Tropical Diseases, miltefosine and single-dose liposomal amphotericin B were developed and have been introduced as a first-line treatment against visceral leishmaniasis. The programme-supported studies evaluated the quality, community acceptance, and cost-effectiveness of indoor residual spraying, insecticide-treated bednets, insecticide-impregnated durable wall linings, insecticidal paint, and environmental management as tools for integrated vector management.4Hirve S Kroeger A Matlashewski G et al.Towards elimination of visceral leishmaniasis in the Indian subcontinent: translating research to practice to public health.PLoS Negl Trop Dis. 2017; 11e0005889Crossref PubMed Scopus (26) Google Scholar Active case detection of visceral leishmaniasis along with other febrile illnesses through health camps and vector control interventions using insecticidal paint or indoor residual spraying as alternative and sustainable strategies in the post-elimination phase of the visceral leishmaniasis programme5Banjara MR Das ML Gurung CK et al.Integrating case detection of visceral leishmaniasis and other febrile illness with vector control in the post-elimination phase in Nepal.Am J Trop Med Hyg. 2019; 100: 108-114Crossref PubMed Scopus (7) Google Scholar has resulted in a positive trend toward visceral leishmaniasis elimination. In The Lancet Global Health, Kristien Cloots and colleagues show, by means of a repeat survey of a cross-sectional study, that transmission of Leishmania donovani in Nepal has decreased significantly between 2006 and 2016.6Cloots K Uranw S Ostyn B et al.Impact of the visceral leishmaniasis elimination initiative on Leishmania donovani transmission in Nepal: a repeat survey.Lancet Glob Health. 2020; 8: e237-e243Summary Full Text Full Text PDF PubMed Scopus (9) Google Scholar The direct agglutination test (DAT) appeared to be useful for monitoring of L donovani transmission. This study suggested that a higher and more specific DAT cutoff titre can be considered to accurately distinguish between low and zero transmission rates in an elimination setting, although this result should be further evaluated. The study provided evidence that the seroprevalence had reduced significantly from 8·4% in 2006 to 4·7% in 2016 (p<0·0001) indicating a very low transmission of visceral leishmaniasis in Nepal.6Cloots K Uranw S Ostyn B et al.Impact of the visceral leishmaniasis elimination initiative on Leishmania donovani transmission in Nepal: a repeat survey.Lancet Glob Health. 2020; 8: e237-e243Summary Full Text Full Text PDF PubMed Scopus (9) Google Scholar A seroprevalence of 8·4% in 2006 and 8·5% in 1996 revealed continued constant visceral leishmaniasis transmission before starting elimination initiatives.6Cloots K Uranw S Ostyn B et al.Impact of the visceral leishmaniasis elimination initiative on Leishmania donovani transmission in Nepal: a repeat survey.Lancet Glob Health. 2020; 8: e237-e243Summary Full Text Full Text PDF PubMed Scopus (9) Google Scholar, 7Joshi AB Sero-epidemiology of visceral leishmaniasis in Southern Nepal and West Bengal of India. Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand1996Google Scholar This study reflects the gains achieved by elimination efforts. Previously visceral leishmaniasis was clustered, but in the past 6–7 years clustering has been less evident. In our 2019 research, which is not yet published, we found 20 visceral leishmaniasis cases scattered in different villages in two hilly districts. The villages were far apart from each other. This unique distribution of visceral leishmaniasis cases suggests that further exploration of disease transmission dynamics is required. New foci of visceral leishmaniasis infection exist, including the geographical expansion of the disease in hilly and mountainous districts. We are still lacking fundamental information about the transmission dynamics of the disease (particularly in areas where the disease is or was until recently absent), as well as knowledge of which factors drive the spread of the disease and what interventions countries can afford. Implementation of active case detection and vector control mass interventions might not be cost-effective for governments when the disease burden is substantially reduced and active cases are detected in wider geographical areas. Geographical expansion, new visceral leishmaniasis foci, and areas with low visceral leishmaniasis endemicity are a challenge for the sustainability of visceral leishmaniasis elimination. Surveys combining the leishmanin skin test and rK39 rapid immunochromatographic test are needed to monitor transmission in a low-incidence country like Nepal. Nepal is an ideal place to see what interruption of transmission means and whether it is an attainable goal. The conversion of individuals who are asymptomatic to the progression of visceral leishmaniasis disease, the role of domestic animals in transmission, and risk assessment in areas with new cases that were previously non-endemic need to be investigated. HIV coinfection with visceral leishmaniasis, relapses among newly treated cases, and development of parasite resistance to drugs also need to be studied further. Xenodiagnostic studies to measure reservoir potential should be explored and identified. Strong collaboration backed by adequate financial support to implement operational research on early case detection, treatment and follow-up of treated cases, vector surveillance particularly in new foci and hilly areas, and non-invasive antigen-based diagnostic tools are essential to sustain the elimination. We declare no competing interests. Impact of the visceral leishmaniasis elimination initiative on Leishmania donovani transmission in Nepal: a 10-year repeat surveyOur findings show that transmission of L donovani in Nepal has decreased significantly between 2006 and 2016, coinciding with the elimination programme. DAT seems useful for monitoring of L donovani transmission. Full-Text PDF Open Access