Optimizing Village-Level Targeting of Active Case Detection to Support Visceral Leishmaniasis Elimination in India

Abstract

BackgroundIndia has made major progress in improving control of visceral leishmaniasis (VL) in recent years, in part through shortening the time infectious patients remain untreated. Active case detection decreases the time from VL onset to diagnosis and treatment, but requires substantial human resources. Targeting approaches are therefore essential to feasibility.MethodsWe analyzed data from the Kala-azar Management Information System (KAMIS), using village-level VL cases over specific time intervals to predict risk in subsequent years. We also graphed the time between cases in villages and examined how these patterns track with village-level risk of additional cases across the range of cumulative village case-loads. Finally, we assessed the trade-off between ACD effort and yield.ResultsIn 2013, only 9.3% of all villages reported VL cases; this proportion shrank to 3.9% in 2019. Newly affected villages as a percentage of all affected villages decreased from 54.3% in 2014 to 23.5% in 2019, as more surveillance data accumulated and overall VL incidence declined. The risk of additional cases in a village increased with increasing cumulative incidence, reaching approximately 90% in villages with 12 cases and 100% in villages with 45 cases, but the vast majority of villages had small cumulative case numbers. The time-to-next-case decreased with increasing case-load. Using a 3-year window (2016–2018), a threshold of seven VL cases at the village level selects 329 villages and yields 23% of cases reported in 2019, while a threshold of three cases selects 1,241 villages and yields 46% of cases reported in 2019. Using a 6-year window increases both effort and yield.ConclusionDecisions on targeting must consider the trade-off between number of villages targeted and yield and will depend upon the operational efficiencies of existing programs and the feasibility of specific ACD approaches. The maintenance of a sensitive, comprehensive VL surveillance system will be crucial to preventing future VL resurgence.

Development and Evaluation of Active Case Detection Methods to Support Visceral Leishmaniasis Elimination in India

“…One of the central challenges for the next phase of the VL elimination program is to ensure timely detection of individual cases and small outbreaks as incidence falls and the disease is no longer perceived as a major threat (Rijal et al, 2019). During the extensive VL assessments conducted in 2013-2015, two major observations led to the design of the ACD methodology evaluated here (Bindroo et al, 2021). First, more than half of all cases in a given year occurred in villages with cases in the previous year.…”

Livestock and rodents within an endemic focus of Visceral Leishmaniasis are not reservoir hosts for Leishmania donovani

“…The humid tropical temperatures of Muzaffarpur range from 14°C in December–January to 32°C in April–May with average annual precipitation of about 1,300 mm during the monsoon season from June to September. Villages with active transmission were selected based on current and past VL history from the Muzaffarpur-TMRC Health and Demographic Surveillance System (HDSS), ongoing since 2007 [ 40 ] and Kala-azar Management Information System (KAMIS) [ 10 ] ( Fig 1 ).…”

“…In this low-incidence setting, attention is focused on early screening in previously endemic areas and intervention in outbreaks. Outbreak investigations consist of surveillance procedures to establish an outbreak based on newly reported case numbers in the region then implementation of relevant interventions, and, when possible, identification of local risk factors to prevent parasite transmission [ 10 ]. To continue to have elimination-level case numbers over the coming years, it will be essential to maintain the ability of the public health system to forecast and monitor outbreaks of VL, as well as to quickly implement effective control measures.…”

Inferring the regional distribution of Visceral Leishmaniasis incidence from data at different spatial scales

“…Case counts of VL are currently monitored at the village level to inform vector control and case detection activities [3], yet villages are treated almost entirely independently; recent observation of any case in a village dictates subsequent years' interventions in that village alone, but not neighbouring villages. This approach to the deployment of active case detection appears to capture a majority of future cases [4] yet inevitably cannot account for sporadic cases in previously unaffected villages. Interventions could be applied more efficiently if sporadically-affected villages were covered within the range of a nearby persistently-affected village, rather than waiting for a response to be triggered within each independently.…”