The role of case proximity in transmission of visceral leishmaniasis in a highly endemic village in Bangladesh
"Visceral leishmaniasis (VL), a fatal parasitic disease transmitted by sandflies, has been targeted for elimination as a public health problem in the Indian subcontinent by 2020. The goal has been reached in the majority of endemic regions in Bangladesh, India and Nepal, but the disease persists in several hotspots. Better understanding of spatial clustering of VL cases and the role of asymptomatically infected individuals in transmission is required to improve control interventions and sustain the elimination target. To address this issue, we have fitted an individual-level spatiotemporal model of VL transmission to geo-located incidence data from Bangladesh to estimate the rate at which VL risk decreases with distance from a case and the potential contribution of asymptomatic individuals to transmission. Our results suggest that VL risk decreases quickly with distance and that symptomatic individuals are the main drivers of transmission, highlighting the potential for spatially-targeted control interventions to reduce transmission".
"In the Indian subcontinent, visceral leishmaniasis (VL) has a strongly clustered distribution. The “index case approach” is promoted both for active case finding and indoor residual spraying (IRS). Uncertainty exists about the optimal radius. Buffer zones of 50–75 m around incident cases have been suggested for active case finding, for IRS the recommendation is to cover a radius of 500 m. Our aim was to establish optimal target areas both for IRS and for (re)active case finding. We plotted incident VL cases on a map per 6-month period (January–June or July–December) and drew buffers of 0 (same household), 50, 75, 100, 200, 300, 400, and 500 m around these cases. We then recorded total population and numbers of VL cases diagnosed over the next 6-month period in each of these buffers and beyond. We calculated incidence rate ratios (IRRs) using the population at more than 500 m from any case as reference category. There was a very strong degree of spatial clustering of VL with IRRs ranging from 45.2 (23.8–85.6) for those living in the same households to 14.6 (10.1–21.2) for those living within 75 m of a case diagnosed, during the previous period. Up to 500 m the IRR was still five times higher than that of the reference category. Our findings corroborate the rationale of screening not just household contacts but also those living within a perimeter of 50–75 m from an index case. For IRS, covering a perimeter of 500 m, appears to be a rational choice."
"The visceral leishmaniasis (VL) elimination programme was launched in the Indian subcontinent (Bangladesh, India and Nepal) in 2005. Although the integrated vector management (IVM) system is one of the important elements highlighted in the Regional VL elimination strategy, indoor residual spraying (IRS) is the sole intervention practice that has been implemented. In fact, in Bangladesh from 1999 to early 2012, no VL vector control was used at all and pre-monsoon IRS was only re-introduced by the national programme in eight high endemic upazilas (sub-districts) in 2012. The present study monitored IRS operation in five upazilas (Fulbaria, Trishal, Mukthagacha, Gaforgaon and Bhaluka). Monitoring took place with the help of using observation check lists and questionnaires included in the WHO/TDR monitoring and evaluation tool kit. The study identified that training of spraymen was insufficient and a supervisor was not always present during spraying. The spraying techniques by all the sprayers were sub-standard. It was also found that all the required personal protective equipment was not provided by the national programme. It is recommended that the national programme should conduct monitoring and evaluation activities to ensure high quality of IRS operations in order to achieve maximum benefit.
"The diagnosis of visceral leishmaniasis (VL) is one of the foremost barriers in the control of this disease, as demonstration of the parasite by splenic/bone marrow aspiration is relatively difficult and requires expertise and laboratory support. The aim of the present study was to find a noninvasive diagnostic approach using the existing recombinant kinesine-39 (rK-39) immunochromatographic nitrocellulose strips test (ICT) with a human sweat specimen for the diagnosis of VL. The investigation was carried out on specimens (blood, sweat, and urine) collected from 58 confirmed VL, 50 confirmed post kala-azar dermal leishmaniasis (PKDL), 36 healthy control, and 35 patients from other diseases. The data obtained from this study reveal that 96.55% clinically confirmed active VL participants were found to be positive when tested against a sweat specimen. Interestingly, the scenario was similar when tested against a blood specimen (96.55% positive by rK-39). Moreover, a test of both sweats and blood specimens from 50 PKDL participants resulted in 100% positivity, whereas no healthy control participants were found to be rK-39 positive. The sensitivity of the rK-39 ICT in sweat specimen was 94.74%, whereas the specificity was 100% in healthy controls from endemic, nonendemic, and other infectious diseases, respectively. No difference was observed in sweat specimen of VL and PKDL cases which signifies its reliability. However, further evaluation of this method on a larger scale could enhance the reliability of the proposed model so that it could be used efficiently in VL management and eradication."
Safety and Effectiveness of Short-Course AmBisome in the Treatment of Post-Kala-Azar Dermal Leishmaniasis: A Prospective Cohort Study in Bangladesh.
A prospective cohort observational study focusing on evauating the effectiveness and safety of AmBisome for PKDL patients residing in a highly VL-endemic area in Bangladesh. Clinical response was monitored regularly up to 12 months after treatment, while safety during treatment and up to 1 month after treatment.
The authors conclude that "short-course 15-mg/kg AmBisome regimen proved safe and effective in the treatment of clinically diagnosed PKDL in Bangladesh, and should be considered a treatment option for routine programmatic use in the VL elimination effort in the Indian subcontinent.
This study demonstrates the potential value of using Leishmania strains isolated from VL patients for monitoring drug sensitivty and resistance emergence, as well as for systematic use in high-throughput screening (HTS) during novel anti-leishmanial drug discovery.
"Introduction: Visceral leishmaniasis (VL) is a fatal parasitic disease caused by a parasite belonging to the Leishmania donovani complex and transmitted by infected female Phlebotomous argentipes sand flies. The VL elimination strategy in the Indian subcontinent (ISC), which has a current goal of reducing the incidence of VL to below 1/10,000 of population by the year 2020, consists of rapid detection and treatment of VL to reduce the number of human reservoirs as well as vector control using indoor residual spraying (IRS). However, as the incidence of VL declines toward the elimination goal, greater targeting of control methods will be required to ensure appropriate early action to prevent the resurgence of VL.
Area covered: We discuss the current progress and challenges in the VL elimination program and strategies to be employed to ensure sustained elimination of VL.
Expert commentary: The VL elimination initiative has saved many human lives; however, for VL elimination to become a reality in a sustained way, an intense effort is needed, as substantial numbers of endemic subdistricts (primary health centers (PHCs) blocks level) are yet to reach the elimination target. In addition to effective epidemiological surveillance, appropriate diagnostic and treatment services for VL at PHCs will be needed to ensure long-term sustainability and prevent reemergence of VL."
Developed by the London School of Hygiene and Tropical Medicine together with the guidance, expertise and training material from KalaCORE partners and the support of UK aid by the UK government, we invite you to join the new open free on-line course on the Control and Elimination of Visceral Leishmaniasis (VL).
The course serves as a unique platform to learn about the practical tools, the requirements and the complexities of VL control and elimination programmes - like those supported by KalaCORE, in South Asia and East Africa.
To register to the course and to find out more information visit https://www.futurelearn.com/courses/visceral-leishmaniasis/