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The role of case proximity in transmission of visceral leishmaniasis in a highly endemic village in Bangladesh

"Author summary

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".

12 Oct 2018
Academic paper
Improving surveillance
Bangladesh

Visceral Leishmaniasis in the Muzaffapur Demographic Surveillance Site: A Spatiotemporal Analysis

Abstract

"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."

 

11 Oct 2018
Academic paper
Improving surveillance
India

Indoor residual spraying for kala-azar vector control in Bangladesh: A continuing challenge

Author summary

"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.

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8 Oct 2018
Academic paper
Training health workers, Operational research
Bangladesh

Open-access Seminar on Leishmaniasis by The Lancet

Abstract

"Leishmaniasis is a poverty-related disease with two main clinical forms: visceral leishmaniasis and cutaneous leishmaniasis. An estimated 0·7–1 million new cases of leishmaniasis per year are reported from nearly 100 endemic countries. The number of reported visceral leishmaniasis cases has decreased substantially in the past decade as a result of better access to diagnosis and treatment and more intense vector control within an elimination initiative in Asia, although natural cycles in transmission intensity might play a role. In east Africa however, the case numbers of this fatal disease continue to be sustained. Increased conflict in endemic areas of cutaneous leishmaniasis and forced displacement has resulted in a surge in these endemic areas as well as clinics across the world. WHO lists leishmaniasis as one of the neglected tropical diseases for which the development of new treatments is a priority. Major evidence gaps remain, and new tools are needed before leishmaniasis can be definitively controlled."
5 Oct 2018
Academic paper
Health education, Training health workers

Noninvasive Sweat-Based Diagnosis of Visceral Leishmaniasis and Post Kala-Azar Dermal Leishmaniasis

Abstract

"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."

1 Oct 2018
Academic paper
Improving surveillance
India

Importance of secondary screening with clinical isolates for anti- leishmania drug discovery

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.

8 Aug 2018
Academic paper
Operational research

Visceral leishmaniasis elimination targets in India, strategies for preventing resurgence

Abstract

"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."

30 Jul 2018
Academic paper
Improving surveillance
India

Insecticide susceptibility status of Phlebotomus argentipes and polymorphisms in voltage-gated sodium channel (vgsc) gene in Kala-azar endemic areas of West Bengal, India

This study evaluated insecticide susceptibility of Phlebotomus argentipes sand flies in West Bengal, India and looked at associated polymorphisms in insecticide target genes. Key findings:

- Sand fly populations were found resistant to DDT but susceptible to deltamethrin and malathion.

- Mutations L1014S and L1014F were also detected. The latter was found associated with deltamethrin/DDT resistance.

The authors conclude that Type II pyrethroid tolerability can be an indication of emergence of resistance against it. Malathion may be used as an alternative in the study areas if needed in future.

2 Jul 2018
Academic paper
Operational research
India

Policy Recommendations From Transmission Modeling for the Elimination of Visceral Leishmaniasis in the Indian Subcontinent

"This paper draws together the key policy-relevant conclusions from recent transmission modeling of VL, and presents new predictions for VL incidence under the interventions recommended by the WHO using the latest transmission models."
1 Jun 2018
Academic paper
India, Bangladesh, Nepal

The initial effectiveness of liposomal amphotericin B (AmBisome) and miltefosine combination for treatment of visceral leishmaniasis in HIV co-infected patients in Ethiopia: A retrospective cohort study

This study examined the initial effectiveness of a combination treatment of AmBisome and miltefosine in HIV / VL co-infected patients in Ethiopia.

1 Jun 2018
Academic paper
Case management
Ethiopia

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