Elimination of visceral leishmaniasis in the Indian subcontinent: a comparison of predictions from three transmission models.

We present three transmission models of visceral leishmaniasis (VL) in the Indian subcontinent (ISC) with structural differences regarding the disease stage that provides the main contribution to transmission, including models with a prominent role of asymptomatic infection, and fit them to recent case data from 8 endemic districts in Bihar, India. Following a geographical cross-validation of the models, we compare their predictions for achieving the WHO VL elimination targets with ongoing treatment and vector control strategies. All the transmission models suggest that the WHO elimination target (<1 new VL case per 10,000 capita per year at sub-district level) is likely to be met in Bihar, India, before or close to 2020 in sub-districts with a pre-control incidence of 10 VL cases per 10,000 people per year or less, when current intervention levels (60% coverage of indoor residual spraying (IRS) of insecticide and a delay of 40days from onset of symptoms to treatment (OT)) are maintained, given the accuracy and generalizability of the existing data regarding incidence and IRS coverage. In settings with a pre-control endemicity level of 5/10,000, increasing the effective IRS coverage from 60 to 80% is predicted to lead to elimination of VL 1-3 years earlier (depending on the particular model), and decreasing OT from 40 to 20days to bring elimination forward by approximately 1year. However, in all instances the models suggest that L. donovani transmission will continue after 2020 and thus that surveillance and control measures need to remain in place until the longer-term aim of breaking transmission is achieved

Impact of IRS: Four-years of entomological surveillance of the Indian Visceral Leishmaniases elimination programme

BACKGROUND In 2005, Bangladesh, India and Nepal agreed to eliminate visceral leishmaniasis (VL) as a public health problem. The approach to this was through improved case detection and treatment, and controlling transmission by the sand fly vector Phlebotomus argentipes, with indoor residual spraying (IRS) of insecticide. Initially, India applied DDT with stirrup pumps for IRS, however, this did not reduce transmission. After 2015 onwards, the pyrethroid alpha-cypermethrin was applied with compression pumps, and entomological surveillance was initiated in 2016. METHODS Eight sentinel sites were established in the Indian states of Bihar, Jharkhand and West Bengal. IRS coverage was monitored by household survey, quality of insecticide application was measured by HPLC, presence and abundance of the VL vector was monitored by CDC light traps, insecticide resistance was measured with WHO diagnostic assays and case incidence was determined from the VL case register KAMIS. RESULTS Complete treatment of houses with IRS increased across all sites from 57% in 2016 to 70% of houses in 2019, rising to >80% if partial house IRS coverage is included (except West Bengal). The quality of insecticide application has improved compared to previous studies, average doses of insecticide on filters papers ranged from 1.52 times the target dose of 25mg/m2 alpha-cypermethrin in 2019 to 1.67 times in 2018. Resistance to DDT has continued to increase, but the vector was not resistant to carbamates, organophosphates or pyrethroids. The annual and seasonal abundance of P. argentipes declined between 2016 to 2019 with an overall infection rate of 0.03%. This was associated with a decline in VL incidence for the blocks represented by the sentinel sites from 1.16 per 10,000 population in 2016 to 0.51 per 10,000 in 2019. CONCLUSION Through effective case detection and management reducing the infection reservoirs for P. argentipes in the human population combined with IRS keeping P. argentipes abundance and infectivity low has reduced VL transmission. This combination of effective case management and vector control has now brought India within reach of the VL elimination targets

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

As India moves toward the elimination of visceral leishmaniasis (VL) as a public health problem, comprehensive timely case detection has become increasingly important, in order to reduce the period of infectivity and control outbreaks. During the 2000s, localized research studies suggested that a large percentage of VL cases were never reported in government data. However, assessments conducted from 2013 to 2015 indicated that 85% or more of confirmed cases were eventually captured and reported in surveillance data, albeit with significant delays before diagnosis. Based on methods developed during these assessments, the CARE India team evolved new strategies for active case detection (ACD), applicable at large scale while being sufficiently effective in reducing time to diagnosis. Active case searches are triggered by the report of a confirmed VL case, and comprise two major search mechanisms: 1) case identification based on the index case's knowledge of other known VL cases and searches in nearby houses (snowballing); and 2) sustained contact over time with a range of private providers, both formal and informal. Simultaneously, house-to-house searches were conducted in 142 villages of 47 blocks during this period. We analyzed data from 5030 VL patients reported in Bihar from January 2018 through July 2019. Of these 3033 were detected passively and 1997 via ACD (15 (0.8%) via house-to-house and 1982 (99.2%) by light touch ACD methods). We constructed multinomial logistic regression models comparing time intervals to diagnosis (30-59, 60-89 and ≥90 days with =90 days compared to the referent of <30 days for ACD vs PCD were 0.88, 0.56 and 0.42 respectively. These ACD strategies not only reduce time to diagnosis, and thus risk of transmission, but also ensure that there is a double check on the proportion of cases actually getting captured. Such a process can supplement passive case detection efforts that must go on, possibly perpetually, even after elimination as a public health problem is achieved

The Influence of Seasonality and Community-Based Health Worker Provided Counselling on Exclusive Breastfeeding - Findings from a Cross-Sectional Survey in India.

Exclusive breastfeeding (EBF) during the first six months of life is considered a high impact but low-cost measure for reducing the morbidity and mortality among children. The current study investigated the association of seasonality and frontline worker(FLW) provided counselling with practice of EBF in Bihar, India.We used the 'Lot Quality Assurance Sampling' technique to conduct a multi-stage sampling survey in 8 districts of Bihar. Regarding EBF, mothers of 0-5 (completed) months old children were asked if they had given only breastmilk to their children during the previous day, while mothers of 6-8 (completed) months old children were inquired about the total duration of EBF. We tested for association between EBF during the previous day with season of interview and EBF for full 6 months with nursing season. We also assessed if receiving counselling on EBF and complementary feeding had any association with relevant EBF indicators.Among the under-6 month old children, 76% received EBF during the previous day, whereas 92% of 6-8 (completed) months old children reportedly received EBF for the recommended duration. Proportion of 0-5 (completed) month old children receiving only breastmilk (during last 24 hours) decreased significantly with increasing age and with change of season from colder to warmer months. Odds of receiving only breastmilk during the previous day was significantly higher during the winter months (Adjusted odds ratio(AOR) = 1.50; 95% CI = 1.37, 1.63) compared to summer. Also, the children nursed primarily during the winter season had higher odds of receiving EBF for 6 months (AOR = 1.90, 95% CI = 1.43, 2.52) than those with non-winter nursing. Receiving FLW-counselling was positively associated with breastfeeding exclusively, even after adjusting for seasonality and other covariates (AOR = 1.82; 95% CI = 1.67, 1.98).Seasonality is a significant but non-modifiable risk factor for EBF. However, FLW-counselling was found to increase practice of EBF irrespective of season. Scale-up of FLW-counselling services, with emphasis on summer months and mothers of older infants, can potentially reduce the impact of seasonality on EBF

Socio-demographic and breast feeding related characteristics of children aged 0 to 8 completed months from 8 districts of Bihar.

<p>LQAS Survey: Rounds 2 to 5.</p

Proportions of 0–5 completed months old children who received only breastmilk during the previous 24 hours, stratified by age and exposure to counselling on exclusive breastfeeding.

<p>Proportions of 0–5 completed months old children who received only breastmilk during the previous 24 hours, stratified by age and exposure to counselling on exclusive breastfeeding.</p

Season-wise trend in the proportions of 0–5 completed months old children who received only breastmilk during the previous 24 hours, stratified by age.

<p>Season-wise trend in the proportions of 0–5 completed months old children who received only breastmilk during the previous 24 hours, stratified by age.</p

Proportion of children aged between 0–5 completed months who were breastfed exclusively during past 24 hours, according to age group.

<p>LQAS Survey: Rounds 2 to 5. (n = 20793).</p

Crude and adjusted associations of exclusive breastfeeding with seasonal variations among children aged 0–5 and 6–8 completed months.

<p>LQAS Survey: Rounds 2 to 5.</p

Proportions of 6–8 completed months old children who were exclusively breastfed for 6 months, stratified by ‘season of nursing’.

<p>Proportions of 6–8 completed months old children who were exclusively breastfed for 6 months, stratified by ‘season of nursing’.</p