An outbreak investigation of visceral leishmaniasis among residents of Dharan town, eastern Nepal, evidence for urban transmission of Leishmania donovani

Efforts toward the Elimination of Visceral Leishmaniasis in South Asia: A Review of Progress in Bhutan

Leishmaniases are a group of diseases under the category of neglected tropical diseases targeted for global elimination. However, they continue to pose major clinical and public health problems, especially among those living in poor socioeconomic conditions. Here, we summarize leishmaniasis elimination efforts in Bhutan. Between 1994 and 2022, Bhutan recorded 54 cases of leishmaniasis across 14 of its 20 districts. There are seven species of Phlebotomus and three species of Sergentomyia sand flies documented in the country. At a subnational level, all endemic districts recorded a visceral leishmaniasis annual incidence <1 per 10,000 population, meeting the regional elimination targets. Serological testing with ELISA and molecular testing with polymerase chain reaction were established at the Royal Center for Disease Control in 2022. A leishmaniasis prevention and management guideline was adopted in 2023 to aid clinicians in diagnosis and management. Active and passive case surveillance was integrated with the national infectious disease early warning and response system. Risk-based entomological surveillance and control have also been prioritized. Climate change may play a major role in rendering districts in the temperate zone favorable for vector proliferation. The country's medical university introduced a diploma course in medical entomology in 2023 to augment the human resources needed for vector surveillance efforts. However, leishmaniasis elimination lacks dedicated programmatic management amid competing priorities for resources against other infectious diseases. Leishmaniasis elimination requires a targeted and programmatic approach in Bhutan, including cross-border collaborative efforts with neighboring Indian states. Bhutan remains highly committed to achieving leishmaniasis elimination targets.

The ongoing risk of Leishmania donovani transmission in eastern Nepal: an entomological investigation during the elimination era

BACKGROUND

Visceral leishmaniasis (VL), a life-threatening neglected tropical disease, is targeted for elimination from Nepal by the year 2026. The national VL elimination program is still confronted with many challenges including the increasingly widespread distribution of the disease over the country, local resurgence and the questionable efficacy of the key vector control activities. In this study, we assessed the status and risk of Leishmania donovani transmission based on entomological indicators including seasonality, natural Leishmania infection rate and feeding behavior of vector sand flies, Phlebotomus argentipes, in three districts that had received disease control interventions in the past several years in the context of the disease elimination effort.

METHODS

We selected two epidemiologically contrasting settings in each survey district, one village with and one without reported VL cases in recent years. Adult sand flies were collected using CDC light traps and mouth aspirators in each village for 12 consecutive months from July 2017 to June 2018. Leishmania infection was assessed in gravid sand flies targeting the small-subunit ribosomal RNA gene of the parasite (SSU-rRNA) and further sequenced for species identification. A segment (~ 350 bp) of the vertebrate cytochrome b (cytb) gene was amplified from blood-fed P. argentipes from dwellings shared by both humans and cattle and sequenced to identify the preferred host.

RESULTS

Vector abundance varied among districts and village types and peaks were observed in June, July and September to November. The estimated Leishmania infection rate in vector sand flies was 2.2% (1.1%-3.7% at 95% credible interval) and 0.6% (0.2%-1.3% at 95% credible interval) in VL and non-VL villages respectively. The common source of blood meal was humans in both VL (52.7%) and non-VL (74.2%) villages followed by cattle.

CONCLUSIONS

Our findings highlight the risk of ongoing L. donovani transmission not only in villages with VL cases but also in villages not reporting the presence of the disease over the past several years within the districts having disease elimination efforts, emphasize the remaining threats of VL re-emergence and inform the national program for critical evaluation of disease elimination strategies in Nepal.

Visceral leishmaniasis in new foci areas of Nepal: Sources and extent of infection

Background & objectives

The successful elimination program of visceral leishmaniasis (VL) in Nepal decreased the incidence to less than 1 per 10,000 population leading to the consolidation phase. However, new VL cases have been recorded from new districts, threatening the elimination goal. This study monitors the geographical spread of VL and identifies potential risk factors.

Methods

VL data of 2017-2020 were obtained from the Epidemiology and Disease Control Division (EDCD) of Nepal and mapped. Telephonic interviews with 13 VL patients were conducted.

Results

The incidence maps indicate that VL is spreading to new areas. The target incidence exceeded four times in hilly and twice in mountainous districts. VL cases occurred in 64 of 77 districts in all three regions (mountainous, hilly and Terai). Interviews showed a correlation between travel history (private, commercial and for studies) and the spread of VL cases to new foci.

Interpretation & conclusion

One major challenge of VL elimination in the maintenance phase is the spread of infection through travelers to new foci areas, which needs to be under continuous surveillance accompanied by vector control activities. This should be confirmed by a large-scale analytical study.

Sero-prevalence of visceral leishmaniasis and its associated factors among asymptomatic individuals visiting Denan health center, southeastern Ethiopia

BACKGROUND

In the Somali region of Ethiopia, visceral leishmaniasis (VL) is a public health concern. However, VL epidemiology and sand fly vectors have not been well studied in various areas of the regional state, including Denan district. Therefore, this study was conducted to determine the sero-prevalence, associated factors, and distribution of sand fly vectors of VL in Denan district, south-eastern Ethiopia.

METHODS

A facility-based cross-sectional study was conducted from April to September 2021 among VL patients with classic signs and symptoms visiting Denan Health Center in south-eastern Ethiopia. Using a convenience sampling method, 187 blood samples were collected from individuals who visited Denan Health Center during the study period. Blood samples were subjected to Direct Agglutination Test for the detection of antibodies to VL. A pre-tested structured questionnaire was also used to gather information on risk factors and other characteristics of knowledge and attitude assessment. Sand flies were also collected from indoor, peri-domestic, mixed forest, and termite mounds using light and sticky traps to determine the fauna and abundance.

RESULTS

The overall sero-prevalence rate was 9.63% (18/187). The sero-prevalence was significantly associated with outdoor sleeping (OR = 2.82), the presence of damp floors (OR = 7.76), and sleeping outdoor near animals (OR = 3.22). Around 53.48% of the study participants had previously heard about VL. Study participants practiced different VL control methods, including bed nets (42%), insecticide spraying (32%), smoking plant parts (14%), and environmental cleaning (8%). In total, 823 sand fly specimens, comprising 12 species in two genera (Phlebotomus and Sergentomyia), were trapped and identified. The most abundant species was Sergentomyia clydei (50.18%), followed by Phlebotomus orientalis (11.42%). Also, a higher proportion of P. orientalis was found in termite mounds (65.43%), followed by mixed forest (37.8%) and peri-domestic (20.83%) habitats.

CONCLUSION

The study demonstrated a 9.63% sero-positivity of VL and a remarkable gap in knowledge, attitude, and practices towards VL. P. orientalis was also detected, which could be a probable vector in this area. Thus, public education should be prioritized to improve the community's awareness of VL and its public health impact. In addition, detailed epidemiological and entomological studies are recommended.

Forty years (1980-2019) of visceral leishmaniasis in Nepal: trends and elimination challenges

BACKGROUND

Visceral leishmaniasis (VL) is an important re-emerging neglected tropical disease associated with poverty. Despite the elimination initiative started in 2005, VL cases have been expanding into geographic areas in Nepal. The present study aims at exploring the trends of VL from 1980 to 2019.

METHODS

This retrospective analysis covers 40 y of VL cases reported by the Epidemiology Diseases Control Division, Nepal. Subgroup analyses for annual incidence were performed by age, sex, seasons, districts and provinces, and VL cases were visualized on in-country maps.

RESULTS

A total of 34 564 cases and 584 deaths of VL were reported during 1980-2019. VL persistently increased until 2006 and was reported from all seven provinces of the country. The highest number of confirmed cases (n=2229) was reported in 2003 and the lowest (n=60) in 1983. VL cases expanded from 12 to 23 endemic districts. The key components of the VL elimination program are early diagnosis; enhanced surveillance; integrated vector management; social mobilization; research and treatment.

CONCLUSIONS

Expansion of VL towards the hilly and mountain regions of Nepal has posed challenges to the elimination program. Urgent VL control measures are required to achieve the elimination goals.

Housing Risk Factors of Four Tropical Neglected Diseases: A Brief Review of the Recent Literature

Alongside peace, education, food, income, a stable ecosystem, sustainable resources and social justice, shelter is a prerequisite for health. According to international human rights law, everyone is entitled to an adequate standard of living, which includes adequate housing. Adequate housing, including access to water and sanitation, plays a critical role in the prevention and management of neglected tropical diseases, which affect over 1 billion people worldwide. Inadequate housing conditions represent a risk factor for many of them, e.g., Chagas disease that affects 6–8 million people worldwide, visceral leishmaniasis that kills 20,000–30,000 people/year, lymphatic filariasis which threatens 859 million people worldwide or dengue that has increased 8–10 fold over the last two decades. Vector control strategies for the above-mentioned diseases have shown their effectiveness and should include systematic and repetitive in-house spraying and individual protection (e.g., impregnated nets), as well as better-quality construction material and techniques and better sanitation infrastructures and practices. Access to adequate housing is a basic human right. The violation of the right to adequate housing may affect the enjoyment of other human rights. Access to adequate housing can strengthen (and facilitate access to) other basic human rights, such as the rights to work, health, security, and education.

Factors associated with the expansion of leishmaniasis in urban areas: a systematic and bibliometric review (1959–2021)

This work describes a systematic and bibliometric review of the factors that contribute to the expansion of leishmaniasis in urban areas. Three scientific databases were used: Scientific Electronic Library (Sci ELO), Scopus and Web of Science, encompassing all original and review articles between 1959 and 2021. Three descriptors were used: “leishmaniasis” AND “urban” AND “rural.” Planning, execution, summarization, and selection processes were performed using StArt ( State of the Art through Systematic Review) software. We obtained a total of 304 articles, 60 of which concerned canine leishmaniasis. The factors associated with the expansion of leishmaniasis in urban areas are interrelated, including socioenvironmental and economic complexity, the type of leishmaniasis, the reservoirs, vectors, deforestation, disorderly occupation of space, poor sanitary conditions, and human migration trends. A lack of diagnosis and underreporting of cases in some regions may reflect the increase of cases seen in urban areas. A majority ( n = 121) of studies were conducted in Brazil, followed by Iran ( n = 43). In relation to publications; in general, output has increased over the years, particularly in 2021. The majority of published studies were in the area of epidemiology ( n = 158).

Replacement of Leishmania (Leishmania) infantum Populations in an Endemic Focus of Visceral Leishmaniasis in Brazil

Visceral leishmaniasis is an important global health problem with an estimated of 50,000 to 90,000 new cases per year. VL is the most serious form of leishmaniasis as it can be fatal in 95% of the cases if it remains untreated. VL is a particularly acute problem in Brazil which contributed with 97% of all cases reported in 2020 in the Americas. In this country, VL affects mainly the poorest people in both urban and rural areas and continues to have a high mortality rate estimated around 8.15%. Here, we performed a temporal parasite population study using whole genome sequence data from a set of 34 canine isolates sampled in 2008, 2012 and 2015 from a re-emergent focus in Southeastern Brazil. Our study found the presence of two distinct sexual subpopulations that corresponded to two isolation periods. These subpopulations diverged hundreds of years ago with no apparent gene flow between them suggesting a process of rapid replacement during a two-year period. Sequence comparisons and analysis of nucleotide diversity also showed evidence of balancing selection acting on transport-related genes and antigenic families. To our knowledge this is the first population genomic study showing a turn-over of parasite populations in an endemic region for leishmaniasis. The complexity and rapid adaptability of these parasites pose new challenges to control activities and demand more integrated approaches to understand this disease in New World foci.

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.

Visceral Leishmaniasis (VL), also known as kala-azar, is a major parasitic disease in South Asia (Indian subcontinent), with 85% of the disease incidence in India. Historically VL had been controlled and almost eliminated with Indoor Residual Spraying (IRS) using dichlorodiphenyltrichloroethane (DDT). However, reinitiating this approach in 2015 failed due to high insecticide resistance in the sand fly vector and poor IRS quality, meaning that VL elimination targets were not met. To improve this the National Vector Borne Disease Control Programme changed to an effective insecticide, alpha-cypermethrin and altered the mode of application to compression pumps. Sentinel sites were established to monitor the entomological indicators, these showed the positive impact of these changes from 2016 to 2019. During this period the overall incidence of disease has decreased, and India is now on track to reach it’s target incidence for VL of less than 1/1000 people at the sub-district (block) level.

A trend prevalence of visceral Leishmaniasis in West Armachiho District, Amhara Region, Northwest Ethiopia

Background

Visceral leishmaniasis (VL) is a disease caused by an obligate intracellular protozoan parasite that affects animals and humans. An estimated 3.2 million people are at risk of VL, and 3700–7400 cases occur annually in Ethiopia. The highest numbers of VL cases have been previously reported from the North Western parts of the country, especially in West Armachiho District. The aim of this study was to determine the trend prevalence of VL at the study area.

Methods

Health center based retrospective data were collected to determine the trend prevalence of VL among patients who had blood examination from January 2010 to August 2015. The blood samples were collected by finger pricking and the infections were confirmed by using rK₃₉ antibody test.

Result

Of the 9299 VL suspected cases, 1948 (21%) were positive for rK₃₉ antibody test. Of these, 1757 (90.2%) were primary kala-azar cases, 167 (8.6%) were relapse and the remaining 24 (1.2%) were post kala-azar dermal leishmaniasis cases.

Conclusions

The prevalence of VL is still high in the study area. Therefore, early case detection, diagnosis, treatment, and timely analysis are essential.

Xenodiagnosis to address key questions in visceral leishmaniasis control and elimination

Visceral leishmaniasis (VL) remains an important public health issue worldwide causing substantial morbidity and mortality. The Indian subcontinent accounted for up to 90% of the global VL burden in the past but made significant progress during recent years and is now moving towards elimination. However, to achieve and sustain elimination of VL, knowledge gaps on infection reservoirs and transmission need to be addressed urgently. Xenodiagnosis is the most direct way for testing the infectiousness of hosts to the vectors and can be used to investigate the dynamics and epidemiology of Leishmania donovani transmission. There are, however, several logistic and ethical issues with xenodiagnosis that need to be addressed before its application on human subjects. In the current Review, we discuss the critical knowledge gaps in VL transmission and the role of xenodiagnosis in disease transmission dynamics along with its technical challenges. Establishment of state of the art xenodiagnosis facilities is essential for the generation of much needed evidence in the VL elimination initiative.

Unravelling the proteomic signature of extracellular vesicles released by drug-resistant Leishmania infantum parasites

Leishmaniasis constitutes the 9^th largest disease burden among all infectious diseases. Control of this disease is based on a short list of chemotherapeutic agents headed by pentavalent antimonials, followed by miltefosine and amphotericin B; drugs that are far from ideal due to host toxicity, elevated cost, limited access, and high rates of drug resistance. Knowing that the composition of extracellular vesicles (EVs) can vary according to the state of their parental cell, we hypothesized that EVs released by drug-resistant Leishmania infantum parasites could contain unique and differently enriched proteins depending on the drug-resistance mechanisms involved in the survival of their parental cell line. To assess this possibility, we studied EV production, size, morphology, and protein content of three well-characterized drug-resistant L. infantum cell lines and a wild-type strain. Our results are the first to demonstrate that drug-resistance mechanisms can induce changes in the morphology, size, and distribution of L. infantum EVs. In addition, we identified L. infantum’s core EV proteome. This proteome is highly conserved among strains, with the exception of a handful of proteins that are enriched differently depending on the drug responsible for induction of antimicrobial resistance. Furthermore, we obtained the first snapshot of proteins enriched in EVs released by antimony-, miltefosine- and amphotericin-resistant parasites. These include several virulence factors, transcription factors, as well as proteins encoded by drug-resistance genes. This detailed study of L. infantum EVs sheds new light on the potential roles of EVs in Leishmania biology, particularly with respect to the parasite’s survival in stressful conditions. This work outlines a crucial first step towards the discovery of EV-based profiles capable of predicting response to antileishmanial agents.

Visceral leishmaniasis is a life-threatening disease caused by Leishmania infantum parasites, which are transmitted by sand flies. In the absence of vaccines, current control of this disease is based on chemotherapy, which is comprised of a very limited arsenal threatened by the emergence and spread of drug-resistant strains. In the shadow of growing concern and treatment failure due to resistance, the characterization of extracellular vesicles (EVs) released by drug-resistant L. infantum parasites could shed some light on the complex nature of drug resistance in Leishmania and increase our understanding of the biology of the parasite. EVs are vesicles secreted by all eukaryotic cells whose contents (proteins, DNA/RNAs, lipids) vary as a function of their cellular origin. Our results demonstrate for the first time that EVs released by drug-resistant parasites are enriched in unique protein markers that reflect the drug-resistance mechanisms involved in the survival of parental cells. These unique proteins included several virulence and transcription factors, as well as drug-resistance genes; this offers a potential benefit for drug-resistant parasites in terms of parasite-to-parasite communication and host-parasite interactions. Collectively, our initial results could serve as a jumping-off point for the future development of novel EV-based diagnostic tools for the detection and appraisal of antimicrobial-resistant Leishmania populations.

Of Drugs and Trypanosomatids: New Tools and Knowledge to Reduce Bottlenecks in Drug Discovery

Leishmaniasis (Leishmania species), sleeping sickness (Trypanosoma brucei), and Chagas disease (Trypanosoma cruzi) are devastating and globally spread diseases caused by trypanosomatid parasites. At present, drugs for treating trypanosomatid diseases are far from ideal due to host toxicity, elevated cost, limited access, and increasing rates of drug resistance. Technological advances in parasitology, chemistry, and genomics have unlocked new possibilities for novel drug concepts and compound screening technologies that were previously inaccessible. In this perspective, we discuss current models used in drug-discovery cascades targeting trypanosomatids (from in vitro to in vivo approaches), their use and limitations in a biological context, as well as different examples of recently discovered lead compounds.

Intensely clustered outbreak of visceral leishmaniasis (kala-azar) in a setting of seasonal migration in a village of Bihar, India

Background

A visceral leishmaniasis outbreak was reported from a village in a low-endemic district of Bihar, India.

Methods

Outbreak investigation with house-to-house search and rapid test of kala-azar suspects and contacts was carried out. Sandfly collection and cone bio-assay was done as part of entomological study.

Results

A spatially and temporally clustered kala-azar outbreak was found at Kosra village in Sheikhpura district with 70 cases reported till December 2018. Delay of more than a year was found between diagnosis and treatment of the index case. The southern hamlet with socio-economically disadvantaged migrant population was several times more affected than rest of the village (attack rate of 19.0% vs 0.5% respectively, OR_MH = 39.2, 95% CI 18.2–84.4). The median durations between onset of fever to first contact with any health services, onset to kala-azar diagnosis, diagnosis to treatment were 10 days (IQR 4–18), 30 days (IQR 17–73) and 1 day (IQR 0.5 to 3), respectively, for 50 kala-azar cases assessed till June 2017. Three-fourths of these kala-azar cases had out-of-pocket medical expenditure for their condition. Known risk factors for kala-azar such as illiteracy, poverty, belonging to socially disadvantaged community, migration, residing in kutcha houses, sleeping in rooms with unplastered walls and non-use of mosquito nets were present in majority of these cases. Only half the dwellings of the kala-azar cases were fully sprayed. Fully gravid female P. argentipes collected post indoor residual spraying (IRS) and low sandfly mortality on cone-bioassay indicated poor effectiveness of vector control.

Conclusions

There is need to focus on low-endemic areas of kala-azar. The elimination programme should implement a routine framework for kala-azar outbreak response. Complete case-finding, use of quality-compliant insecticide and coverage of all sprayable surfaces in IRS could help interrupt transmission during outbreaks.

Environmental and socioeconomic risk factors associated with visceral and cutaneous leishmaniasis: a systematic review

We performed a systematic review of the literature published since 1900 about leishmaniasis a neglected vector-borne disease, focused on environmental and social risk factors for visceral (VL) and cutaneous leishmaniasis (CL) to better understand their impact on the incidence of disease. The search terms were "leishmaniasis" AND "risk factors" using Google Scholar, PudMed, and Scielo. We reviewed 177 articles, 95 studies for VL, 75 for CL, and 7 on both forms. We identified 14 categories of risk factors which were divided into three groups: socioeconomic (7), environmental (5), and climate (2) variables. Socioeconomic factors were also associated with disease incidence in vulnerable human populations of arid and tropical developing regions. Environmental and climate factors showed significant associations with the incidence of VL and CL in all the studies that considered them. Proximity to natural vegetation remnants increased disease risk in both the New and Old World while the climate conditions favorable for disease transmission differed among regions. We propose a common conceptual framework for both clinical forms that highlights networks of interaction among risk factors. In both clinical forms, the interplay of these factors played a major role in disease incidence. Although there are similarities in environmental and socioeconomic conditions that mediate the transmission cycle of tropical, arid, and Mediterranean regions, the behavior of vector and reservoirs in each region is different. Special attention should be given to the possibility of vector adaptation to urban environments in developing countries where populations with low socioeconomic status are particularly vulnerable to the disease.

New Strategies and Biomarkers for the Control of Visceral Leishmaniasis

Effective diagnosis and treatment of visceral leishmaniasis, together with the study of vectors and reservoirs, can lead to a better understanding of the parasite transmission dynamics and the development of more efficient control measures. Recent studies have applied new methodologies and biomarkers, and these have contributed to the early and rapid diagnosis of the disease; assessment of success of pharmacological treatments; efficient monitoring of immunosuppressed individuals; and to population screening for field trials of vaccine efficacy. This opinion article proposes an update to the diagnostic tools for visceral leishmaniasis and their rational and combined use to establish the real prevalence of infection or of exposure to Leishmania in endemic areas.

Housing Characteristics and Leishmaniasis: A Systematic Review

Leishmaniasis is a major neglected tropical disease associated with high rates of disability and death. This disease is associated with poverty, which can be reflected in housing quality, especially in rural areas. This systematic review found that mud walls with cracks and holes, damp, and dark houses were risk factors for transmission of leishmaniasis. These characteristics create favorable conditions for sand fly breeding and resting as sand flies prefer humidity, warmth, and protection from sunlight during the day. Housing interventions might be a promising research area with a special focus on education as individual and collective protection for the effective control of leishmaniasis.

Barriers of Visceral Leishmaniasis reporting and surveillance in Nepal: comparison of governmental VL-program districts with non-program districts

OBJECTIVES

At the time when Nepal is on the verge of reaching the maintenance phase of the Visceral Leishmaniasis (VL) elimination program, the country is facing new challenges. The disease has expanded to 61 of the country's 75 districts including previously non-endemic areas where there is no control or patient management program in place. This study aimed to assess which elements of the surveillance and reporting systems need strengthening to identify cases at an early stage, prevent further transmission and ensure sustained VL elimination.

METHODS

In a cross-sectional mixed-method study, we collected data from two study populations in VL program and non-program districts. From February to May 2016, structured interviews were conducted with 40 VL patients, and 14 in-depth and semi-structured interviews were conducted with health managers.

RESULTS

The median total delay from onset of symptoms to successful reporting to the Ministry of Health was 68.5 days in the VL-program and 83 days in non-program districts. The difference in patient's delay from the onset of symptoms to seeking health care was 3 days in VL-program and 20 days in non-program districts. The diagnostic delay (38.5 days and 36 days, respectively), treatment delay (1 vs. 1 days) and reporting delay (45 vs. 36 days) were similar in program and non-program districts. The diagnostic delay increased three-fold from 2012, while treatment and reporting delay remained unchanged. The main barriers to surveillance were: (i) lack of access and awareness in non-program districts; (ii) growing private sector not included in and not participating to referral, treatment and reporting; (iii) lack of cooperation and coordination among stakeholders for training and deployment of interventions; (iv) insufficient validation, outreach and process optimisation of the reporting system.

CONCLUSIONS

Corrective measures are needed to maintain the achievements of the VL elimination campaign and prevent resurgence of the disease in Nepal. A clear patient referral structure, reinforcement of report notification and validation and direct relay of data by local hospitals and the private sector to the district health offices are needed to ensure prompt treatment and timely and reliable information to facilitate a responsive system of interventions.

Scoping review on vector-borne diseases in urban areas: transmission dynamics, vectorial capacity and co-infection

BACKGROUND

Transmission dynamics, vectorial capacity, and co-infections have substantial impacts on vector-borne diseases (VBDs) affecting urban and suburban populations. Reviewing key factors can provide insight into priority research areas and offer suggestions for potential interventions.

MAIN BODY

Through a scoping review, we identify knowledge gaps on transmission dynamics, vectorial capacity, and co-infections regarding VBDs in urban areas. Peer-reviewed and grey literature published between 2000 and 2016 was searched. We screened abstracts and full texts to select studies. Using an extraction grid, we retrieved general data, results, lessons learned and recommendations, future research avenues, and practice implications. We classified studies by VBD and country/continent and identified relevant knowledge gaps. Of 773 articles selected for full-text screening, 50 were included in the review: 23 based on research in the Americas, 15 in Asia, 10 in Africa, and one each in Europe and Australia. The largest body of evidence concerning VBD epidemiology in urban areas concerned dengue and malaria. Other arboviruses covered included chikungunya and West Nile virus, other parasitic diseases such as leishmaniasis and trypanosomiasis, and bacterial rickettsiosis and plague. Most articles retrieved in our review combined transmission dynamics and vectorial capacity; only two combined transmission dynamics and co-infection. The review identified significant knowledge gaps on the role of asymptomatic individuals, the effects of co-infection and other host factors, and the impacts of climatic, environmental, and socioeconomic factors on VBD transmission in urban areas. Limitations included the trade-off from narrowing the search strategy (missing out on classical modelling studies), a lack of studies on co-infections, most studies being only descriptive, and few offering concrete public health recommendations. More research is needed on transmission risk in homes and workplaces, given increasingly dynamic and mobile populations. The lack of studies on co-infection hampers monitoring of infections transmitted by the same vector.

CONCLUSIONS

Strengthening VBD surveillance and control, particularly in asymptomatic cases and mobile populations, as well as using early warning tools to predict increasing transmission, were key strategies identified for public health policy and practice.

Towards elimination of visceral leishmaniasis in the Indian subcontinent-Translating research to practice to public health

BACKGROUND

The decade following the Regional Strategic Framework for Visceral Leishmaniasis (VL) elimination in 2005 has shown compelling progress in the reduction of VL burden in the Indian subcontinent. The Special Programme for Research and Training in Tropical Diseases (TDR), hosted by the World Health Organization (WHO) and other stakeholders, has coordinated and financed research for the development of new innovative tools and strategies to support the regional VL elimination initiative. This paper describes the process of the TDR's engagement and contribution to this initiative.

METHODOLOGY/PRINCIPAL FINDINGS

Multiple databases were searched to identify 152 scientific papers and reports with WHO funding or authorship affiliation around the following 3 framework strategies: detection of new cases, morbidity reduction, and prevention of infection. TDR has played a critical role in the evaluation and subsequent use of the 39-aminoacid-recombinant kinesin antigen (rK39) rapid diagnostic test (RDT) as a confirmatory test for VL in the national program. TDR has supported the clinical research and development of miltefosine and single-dose liposomal amphotericin B as a first-line treatment against VL. TDR has engaged with in-country researchers, national programme managers, and partners to generate evidence-based interventions for early detection and treatment of VL patients. TDR evaluated the quality, community acceptance, and cost effectiveness of indoor residual spraying, insecticide-treated bed nets, insecticide-impregnated durable wall linings, insecticidal paint, and environmental management as tools for integrated vector management in reducing sandfly density.

CONCLUSIONS/SIGNIFICANCE

TDR's engagement with country policy makers, scientists, and clinicians in the development of effective diagnosis, treatment, case detection, and vector control represents an important example of TDR's stewardship toward the elimination of VL in the Indian subcontinent.

Insecticide resistance in phlebotomine sandflies in Southeast Asia with emphasis on the Indian subcontinent

BACKGROUND

Visceral leishmaniasis, commonly known as kala-azar in India, is a global public health problem. In Southeast Asia, Bangladesh, Bhutan, India, Nepal, Sri Lanka and Thailand are endemic for visceral leishmaniasis. The role of sandflies as the vector of kala-azar was first confirmed in 1942 in India. Insecticide resistance in Phlebotomus argentipes Annandale and Brunetti, the vector of kala-azar in the Indian subcontinent, was first reported in 1987 in Bihar, India. This article provides a scoping review of the studies undertaken from 1959 to 2015 on insecticide resistance in P. argentipes and P. papatasi (Scopoli), the vectors of visceral and cutaneous leishmaniasis respectively, in Southeast Asia, mainly in Bangladesh, India, Nepal and Sri Lanka.

RESULTS

Studies undertaken in areas of Bihar and West Bengal in India where kala-azar is endemic have reported resistance of P. argentipes to DDT, while in non-endemic areas it has been reported to be susceptible. In areas of Nepal bordering India, there are indications of resistance to DDT; biochemical resistance has been reported in Sri Lanka. No laboratory studies have been undertaken in Bangladesh; however, the sandfly vector is reported to be still susceptible to pyrethroids in all kala-azar endemic areas in the aforementioned countries.

CONCLUSIONS

Studies are needed to determine the resistance of sandfly vectors to all available classes of potential insecticides in kala-azar endemic areas. There is a need to assess the impact of indoor residual spraying with DDT and pyrethroids on the incidence of kala-azar in India where 54 districts remain endemic for the disease, strengthen entomological surveillance capacity, and develop and implement an insecticide management plan. Alpha-cypermethrin indoor residual spraying has been introduced in 33 kala-azar endemic districts in Bihar State of India in a pilot trial; the outcomes should be used to inform decisions on expanding coverage with alpha-cypermethrin in all remaining endemic districts to achieve the revised goal of elimination of visceral leishmaniasis by 2020.

Transmission Dynamics of Visceral Leishmaniasis in the Indian Subcontinent - A Systematic Literature Review

Background

As Bangladesh, India and Nepal progress towards visceral leishmaniasis (VL) elimination, it is important to understand the role of asymptomatic Leishmania infection (ALI), VL treatment relapse and post kala-azar dermal leishmaniasis (PKDL) in transmission.

Methodology/ Principal Finding

We reviewed evidence systematically on ALI, relapse and PKDL. We searched multiple databases to include studies on burden, risk factors, biomarkers, natural history, and infectiveness of ALI, PKDL and relapse. After screening 292 papers, 98 were included covering the years 1942 through 2016. ALI, PKDL and relapse studies lacked a reference standard and appropriate biomarker. The prevalence of ALI was 4–17-fold that of VL. The risk of ALI was higher in VL case contacts. Most infections remained asymptomatic or resolved spontaneously. The proportion of ALI that progressed to VL disease within a year was 1.5–23%, and was higher amongst those with high antibody titres. The natural history of PKDL showed variability; 3.8–28.6% had no past history of VL treatment. The infectiveness of PKDL was 32–53%. The risk of VL relapse was higher with HIV co-infection. Modelling studies predicted a range of scenarios. One model predicted VL elimination was unlikely in the long term with early diagnosis. Another model estimated that ALI contributed to 82% of the overall transmission, VL to 10% and PKDL to 8%. Another model predicted that VL cases were the main driver for transmission. Different models predicted VL elimination if the sandfly density was reduced by 67% by killing the sandfly or by 79% by reducing their breeding sites, or with 4–6y of optimal IRS or 10y of sub-optimal IRS and only in low endemic setting.

Conclusion/ Significance

There is a need for xenodiagnostic and longitudinal studies to understand the potential of ALI and PKDL as reservoirs of infection.

The role of asymptomatic Leishmania infection (ALI), PKDL and VL relapse in transmission is unclear as VL elimination is achieved in the Indian subcontinent. ALI, PKDL and relapse studies lacked a reference standard and appropriate biomarker. ALI was 4–17-fold more prevalent than VL. The risk of ALI was higher in VL case contacts. Most infections remained asymptomatic or resolved spontaneously. The natural history of PKDL showed variability. Twenty nine percent had no past history of VL treatment. The risk of VL relapse was higher with HIV co-infection. Modelling studies predicted different effects. Early diagnosis was unlikely to eliminate VL in the long term. ALI was predicted to contribute to 82% of the overall transmission, VL to 10% and PKDL to 8%. Another model predicted that VL cases were the main driver for transmission. VL elimination was predicted if the sandfly density was reduced by 67% by killing the sandfly or by 79% by reducing their breeding sites, or with 4–6y of optimal IRS or 10y of sub-optimal IRS and only in low endemic setting. There is a need for more studies to fully understand the potential of ALI and PKDL as reservoirs of infection.

Climate Change and Spatiotemporal Distributions of Vector-Borne Diseases in Nepal--A Systematic Synthesis of Literature

Background

Despite its largely mountainous terrain for which this Himalayan country is a popular tourist destination, Nepal is now endemic for five major vector-borne diseases (VBDs), namely malaria, lymphatic filariasis, Japanese encephalitis, visceral leishmaniasis and dengue fever. There is increasing evidence about the impacts of climate change on VBDs especially in tropical highlands and temperate regions. Our aim is to explore whether the observed spatiotemporal distributions of VBDs in Nepal can be related to climate change.

Methodology

A systematic literature search was performed and summarized information on climate change and the spatiotemporal distribution of VBDs in Nepal from the published literature until December2014 following providing items for systematic review and meta-analysis (PRISMA) guidelines.

Principal Findings

We found 12 studies that analysed the trend of climatic data and are relevant for the study of VBDs, 38 studies that dealt with the spatial and temporal distribution of disease vectors and disease transmission. Among 38 studies, only eight studies assessed the association of VBDs with climatic variables. Our review highlights a pronounced warming in the mountains and an expansion of autochthonous cases of VBDs to non-endemic areas including mountain regions (i.e., at least 2,000 m above sea level). Furthermore, significant relationships between climatic variables and VBDs and their vectors are found in short-term studies.

Conclusion

Taking into account the weak health care systems and difficult geographic terrain of Nepal, increasing trade and movements of people, a lack of vector control interventions, observed relationships between climatic variables and VBDs and their vectors and the establishment of relevant disease vectors already at least 2,000 m above sea level, we conclude that climate change can intensify the risk of VBD epidemics in the mountain regions of Nepal if other non-climatic drivers of VBDs remain constant.

Risk factors of visceral leishmaniasis: a case control study in north-western Ethiopia

Background

Visceral leishmaniasis (VL, also called ‘’kala-azar”), is a life threatening neglected tropical infectious disease which mainly affects the poorest of the poor. VL is prevalent in Ethiopia particularly in the northwest of the country. Understanding the risk factors of VL infection helps in its prevention and control. The aim of the present study was to identify the factors associated with VL.

Methods

A case–control study was carried out during the period of January-July 2013 in northwest Ethiopia. Cases and controls were diagnosed using clinical presentation, the rk39 rapid diagnostic test and Direct Agglutination Test (DAT). A total of 283 (84.8% males versus 15.2% females) participants were interviewed. 90 cases and 193 controls were involved, matched by age, sex and geographical location with a ratio of 1:2 (case: controls). Univariate and backward multivariate conditional logistic regression were used to identify risk factors of VL.

Results

Elevated odds of VL was associated with goat ownership (OR = 6.4; 95%: confidence interval [Cl]: 1.5-28.4), living in houses with cracked wall (OR = 6.4; 95% Cl: 1.6-25.6), increased family size (OR = 1.3; 95% Cl: 1.0-1.8) and the number of days spent in the farm field (OR = 1.1; 95% Cl: 1.0-1.2). However, daily individual activities around the home and farm fields, mainly sleeping on a bed (OR = 0.2; 95%: Cl 0.03-0.9), sleeping outside the house under a bed net (OR = 0.1; 95% Cl: 0.02-0.36)] and smoking plant parts in the house during the night time (OR = 0.1; 95% Cl: 0.01-0.6) were associated with decreased odds of being VL case.

Conclusion

Our findings showed that use of bed net and smoke could be helpful for the prevention of VL in the area particularly among individuals who spend most of their time in the farm. VL control effort could be focused on improving housing conditions, such as sealing cracks and crevices inside and outside houses. Further research is warranted to elucidate the role of goats in the transmission of L. donovani, assess the impact of bed nets and the role of the traditional practice of smoking plants.

Global distribution maps of the leishmaniases

The leishmaniases are vector-borne diseases that have a broad global distribution throughout much of the Americas, Africa, and Asia. Despite representing a significant public health burden, our understanding of the global distribution of the leishmaniases remains vague, reliant upon expert opinion and limited to poor spatial resolution. A global assessment of the consensus of evidence for leishmaniasis was performed at a sub-national level by aggregating information from a variety of sources. A database of records of cutaneous and visceral leishmaniasis occurrence was compiled from published literature, online reports, strain archives, and GenBank accessions. These, with a suite of biologically relevant environmental covariates, were used in a boosted regression tree modelling framework to generate global environmental risk maps for the leishmaniases. These high-resolution evidence-based maps can help direct future surveillance activities, identify areas to target for disease control and inform future burden estimation efforts.

Trend analysis of visceral leishmaniasis at Addis Zemen health center, Northwest Ethiopia

BACKGROUND

Visceral leishmaniasis (VL) is a systemic disease caused by the Leishmania donovani complex. It is one of the fatal diseases if left untreated. In Ethiopia, there are many VL endemic foci. The aim of this study was to determine the trends of VL in the study area.

METHODOLOGY

A retrospective study was conducted at Addis Zemen health center from September 2005 to August 2011. Data were collected from laboratory registration book and entered and analyzed by using SPSS version 20 software and P value of ≤0.05 was considered statistically significant.

RESULT

A total of 7161 VL suspected cases were reported in the study area. The overall prevalence of VL was 2801 (39.1%). Of the 2801 VL positive cases, the highest annual prevalence, 988 (46.8%), was reported in 2005 but the trend gradually decreases. Majority of the VL confirmed cases were in the age groups of 5-14 years and males were more affected.

CONCLUSION

The prevalence of VL in the study area was high in early 2005 but, gradually, the trend has been decreased and it becomes one of VL endemic foci in Ethiopia.