Determinants of Visceral Leishmaniasis: A Case-Control Study in Gedaref State, Sudan

Prevalence of human visceral leishmaniasis and its risk factors in Eastern Africa: a systematic review and meta-analysis

Introduction

Visceral Leishmaniasis, also known as kala-azar, is a potentially fatal, neglected tropical disease caused by the protozoan parasite Leishmania and transmitted through infected sandflies. It is one of the major global public health problems and contributors to economic crisis among people. Though different studies investigated human visceral leishmaniasis in Eastern Africa, the findings were inconsistent and inconclusive enough, and there is no representative data on this devastating public health concern. Therefore, this systematic review and meta-analysis aimed to determine the pooled prevalence and risk factors associated with human visceral leishmaniasis in Eastern Africa.

Methods

The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA 2020) guidelines were followed for this study. Databases such as PubMed/MEDLINE, CINAHL, LIVIVO, African Journals Online, African Index Medicus (AIM), HINARI, Science Direct, Web of Science, Cochrane Library, Google Scholar, Semantic Scholar, and Google were used to retrieve all the relevant articles. The search was carried out from 23 May 2024 to 17 July 2024. Data were analyzed using STATA 17 software to determine the pooled prevalence of human visceral leishmaniasis with a 95% confidence interval using a random-effects model.

Result

In this meta-analysis, thirty-nine articles with 40,367 study participants were included. The overall pooled prevalence of human visceral leishmaniasis in Eastern Africa was 26.16% [95%; CI: 19.96, 32.36%; I2 = 99.67%; p = 0.00]. Gender, age, family size, presence of termite hill/mound, presence of cattle/domestic animals, outdoor sleeping, presence of VL infected family member/s, and presence of water source/pathway near home were the risk factors significantly associated with human visceral leishmaniasis.

Conclusion

The recorded pooled prevalence of human visceral leishmaniasis in Eastern Africa underscores the urgent need for comprehensive intervention strategies. This includes rigorous health education for residents, covering the disease's cause, transmission, vector breeding sites, and prevention mechanisms.

Sero-Prevalence of Visceral Leishmaniasis and Associated Risk Factors among Febrile Patients Attending Metema Hospital, West Gondar Zone, North West Ethiopia

INTRODUCTION

In Ethiopia, visceral leishmaniasis (VL) is a public health concern that has been spreading to new endemic foci in recent years. An estimated 3.2 million people are at risk of infection, with 3700-7400 new cases yearly. Thus, the study aimed to determine the prevalence of VL and associated risk factors among febrile patients attending Metema Hospital, North West Ethiopia.

METHODS

A hospital-based cross-sectional study was conducted on 404 febrile patients attending Metema Hospital from February 2021 to June 2021. The test for VL was done using an immune-chromatographic test (RK39) according to the manufacturer's instructions (InBios International Inc., USA). An interviewer-administered, pretested questionnaire was used to collect data on risk factors associated with VL. Logistic regression and Chi-square assessed the association between VL and the associated risk factors.

REULTS

The overall prevalence of visceral leishmaniasis was 18.8% (76/404), with a higher prevalence of VL in males, in the age category between 21 and 30, in study participants who completed elementary school, and in those who earned less than 500 birr monthly compared to their counterparts. Houses with thatched roofs (adjusted odd ratio (AOR) = 17.648, 95CI = 6.549,47.563), houses with mud walls (AOR = 2.538, 95% CI = 1.187-5.411), cattle ownership (AOR = 3.173, 95% CI = 1.286-7.826), dog ownership (AOR = 2,533, 95% CI = 1.256-5.111), presence of Acacia trees near houses (AOR = 1.975, 95% CI:1.004-3.886), presence of Balanites tree (AOR = 3.015, 95% CI = 1.610-5.992), and outdoor sleeping (AOR = 2.259, 95% CI: 1.107-14.607) were the predictors of VL in the present study.

CONCLUSIONS

In the study area, VL is still very common. Thus, preventing and controlling infection in the area is largely dependent on raising community awareness of VL prevention and control measures and implementing the necessary interventions on the determinants that have been identified.

Epidemiological profile of visceral leishmaniasis in northern Morocco (2009-2018)

Introduction

visceral leishmaniasis (VL) represents the most serious and severe form of leishmaniasis in Northern Morocco. In this context, the objective of this study was to describe the epidemiological profile of VL in the Tangier Tetouan Al-Hoceima region from 2009 to 2018.

Methods

the epidemiologic data was collected from April 28th, 2019 to February 2nd, 2020 from files and investigation reports of cases. Additionally, annual reports for VL from the health services and provincial laboratories of parasitology were consulted. The analysis was conducted using statistical package for the social sciences (SPSS) v26 software.

Results

the study included 304 cases. Chefchaouen province was the highest endemic area (54.5%). The cases in the spring reached 36.5% and were characterized by age ≤5 years old (78.8%), male gender (M/F=1.3) and rural residents (91.4%). The number of inhabitants per household of cases was >5 persons (68.5%). A total of 94.3% and 98% had no suspect cases around or in their homes, respectively. Farmers accounted for 74.5% of cases. Signs of fever were present in 17.4% of cases, with 67.3% of these cases presenting these signs for a duration of more than 30 days. A total of 64.2% cases were diagnosed within a month. The serological test was used for diagnosis in 67.1% of cases and for the treatment, glunantime® was used in all cases (100%).

Conclusion

to eliminate the VL infection, it's necessary to monitor the entomological, mammalogical investigation. Also, to activate the Integrated Vector Control Management Committee at the most endemic province and to inform the community as well as the professionals of health about the VL control measures. A correlational study of the VL socio-economic and climate factors is recommended.

Social Demographic Characteristics Associated with Visceral Leishmaniasis in West Pokot, Kenya

Visceral leishmaniasis is a tropical disease with a significant global public health burden. This study aimed to determine the social demographic characteristics associated with visceral leishmaniasis in West Pokot of Kenya. A mixed-methods research design was adopted where household questionnaires and key informant interviews were administered. Quantitative data was analyzed using SPSS version 22, and qualitative data were analyzed to establish patterns for interpretation. Male children aged 10 years or younger were the most infected by Leishmania donovani in the community. The hospital record indicated that 60% of previously treated visceral leishmaniasis patients were severely malnourished during admission. Risk factors associated with the disease included low formal education (adjusted odds ratio [aOR] = 4.39; 95% CI = 1.66-11.59; P <0.05), peasant farming (aOR = 8.49; 95% CI = 2.77-26.00; P <0.05), and dog ownership (aOR = 4.86; 95% CI = 1.87-12.60; P <0.05). Social demographic risk factors for visceral leishmaniasis remain a major public health concern in West Pokot.

Re-emergence and influencing factors of mountain-type zoonotic visceral leishmaniasis in the extension region of Loess Plateau, China

OBJECTIVE

To understand the epidemiological distribution characteristics of mountain-type zoonotic visceral leishmaniasis (MT-ZVL) in Yangquan City, Shanxi Province, China, from 2006 to 2021, to explore the influencing factors leading to the re-emergence of the epidemic, and to provide a basis for the formulation of targeted control strategies.

METHODS

Case information spanning from 2006 to 2021 in Yangquan City was collected for a retrospective case-control study conducted from June to September 2022. A 1:3 matched ratio was employed. A questionnaire was utilized to gather data on basic information, demographic characteristics, awareness of MT-ZVL knowledge, residence, and dog breeding and living habits. The study employed a multifactorial conditional stepwise logistic regression model to analyze the influencing factors.

RESULTS

A total of 508 subjects was analyzed. Risk factors for MT-ZVL included the use of soil/stone/concrete as building materials (OR = 3.932), presence of nearby empty/stone stack houses (OR = 2.515), dog breeding (OR = 4.215), presence of stray dogs (OR = 2.767), and neighbor's dog breeding (OR = 1.953). Protective factors comprised knowledge of MT-ZVL (OR = 0.113) and using mosquito repellents (OR = 0.388). The findings indicate significant associations between environmental and behavioral factors and MT-ZVL incidence in Yangquan City, Shanxi Province, China, from 2006 to 2021. These results underscore the importance of public awareness campaigns and targeted interventions aimed at reducing exposure to risk factors and promoting protective measures to mitigate the re-emergence of MT-ZVL outbreaks.

CONCLUSION

House building materials, presence of neighboring empty houses, breeding domestic dogs and distribution of stray dogs surrounding the home are risk factors for MT-ZVL. Awareness of MT-ZVL and implementation of preventive measures during outdoor activities in summer and autumn are protective and may reduce the risk of MT-ZVL.

Spatio-Temporal Analysis and Clinical-Epidemiological Characterization of Visceral Leishmaniasis in Maranhão, Brazil, from 2009 to 2020

This study was carried out to identify the spatial distribution and characterize the clinical-epidemiological profile of Visceral Leishmaniasis (VL) in Maranhão state, Brazil, from 2009 to 2020. This descriptive ecological study collected sociodemographic and clinical data of VL cases from the Brazilian Notifiable Diseases Information System database. A spatial autocorrelation analysis (Moran statistics) was performed. From 2009 to 2020, 5699 cases of VL were reported, with incidence of 6.5 cases/100,000 and prevalence of 7.1 cases/100,000. The temporal analysis showed a significant growth in incidence from 2009 to 2018, followed by a significant decrease between 2019 and 2020. The Moran map shows hotspots of high values in the central-west and central-east regions, and hotspots of low values in the northern region of Maranhão. The profile of patients affected by VL comprises males (OR = 1.8; IC95% = 1.72-1.92), aged under 14 years, brown, and with incomplete elementary schooling. The main symptoms reported were fever, fatigue, and edema. The main diagnostic method was laboratory. The mortality rate was 6.8%, and co-infection with HIV was reported by 8.5% of patients. The results of this study indicated the increase in incidence and lethality, as well as the expansion, of leishmaniasis in the state of Maranhão.

Sex-structured disease transmission model and control mechanisms for visceral leishmaniasis (VL)

BACKGROUND

Leishmaniasis are a group of diseases caused by more than 20 species of the protozoan that are transmitted through the bite of female sand fly. The disease is endemic to 98 countries of the world. It affects most commonly the poorest of the poor and mainly males. Several research has been conducted to propose disease control strategies. Effective medical care, vector control, environmental hygiene, and personal protection are the mainstays of the current preventative and control methods. The mathematical models for the transmission dynamics of the disease studied so far did not consider the sex-biased burden of the disease into consideration.

METHODOLOGY

Unlike the previous VL works, this study introduces a new deterministic sex-structured model for understanding the transmission dynamics of visceral leishmaniasis. Basic properties of the model including basic reproduction number ([Formula: see text]), and conditions for the existence of backward bifurcation of the model are explored. Baseline parameter values were estimated after the model was fitted to Ethiopia's VL data. Sensitivity analysis of the model was performed to identify the parameters that significantly impact the disease threshold. Numerical simulations were performed using baseline parameter values, and scenario analysis is performed by changing some of these parameters as appropriate.

CONCLUSION

The analysis of the model shows that there is a possibility for a backward bifurcation for [Formula: see text], which means bringing [Formula: see text] to less than unity may not be enough to eradicate the disease. Our numerical result shows that the implementation of disease-preventive strategies, as well as effectively treating the affected ones can significantly reduce the disease prevalence if applied for more proportion of the male population. Furthermore, the implementation of vector management strategies also can considerably reduce the total prevalence of the disease. However, it is demonstrated that putting more effort in treating affected reservoir animals may not have any significant effect on the overall prevalence of the disease as compared to other possible mechanisms. The numerical simulation infers that a maximum of 60% of extra preventative measures targeted to only male population considerably reduces the total prevalence of VL by 80%. It is also possible to decrease the total prevalence of VL by 69.51% when up to 50% additional infected males receive treatment with full efficacy. Moreover, applying a maximum of 15% additional effort to reduce the number of vectors, decreases the total VL prevalence by 57.71%. Therefore, in order to reduce the disease burden of visceral leishmaniasis, public health officials and concerned stakeholders need to give more emphasis to the proportion of male humans in their intervention strategies.

Vaccine value profile for leishmaniasis

Leishmania infections are global, occurring in 98 countries and all World Health Organization (WHO) regions with 600 million to 1 billion people at risk of infection. Visceral leishmaniasis is associated with almost 20,000 reported deaths annually, with children under 5 years of age being at the greatest risk of mortality. Amongst WHO-recognised Neglected Tropical Diseases (NTDs), leishmaniasis is one of the most important in terms of mortality and morbidity. With an increasing global burden of disease and a growing threat from climate change, urbanisation and drug resistance, there remains an imperative to develop leishmaniasis vaccines. New tools to understand correlates of protection and to assess vaccine efficacy are being developed to ease the transition into larger scale efficacy trials or provide alternate routes to licensure. Early indications suggest a diverse portfolio of manufacturers exists in endemic countries with an appetite to develop leishmaniasis vaccines. This Vaccine Value Profile (VVP) provides a high-level, comprehensive assessment of the currently available data to inform the potential public health, economic, and societal value of leishmaniasis vaccines. The leishmaniasis VVP was developed by a working group of subject matter experts from academia, public health groups, policy organizations, and non-profit organizations. All contributors have extensive expertise on various elements of the leishmaniasis VVP and have collectively described the state of knowledge and identified the current gaps. The VVP was developed using only existing and publicly available information.

Clinical features, immunological interactions and household determinants of visceral leishmaniasis and malaria coinfections in West Pokot, Kenya: protocol for an observational study

INTRODUCTION

Visceral leishmaniasis (VL) and malaria are two deadly parasitic diseases that coexist in West Pokot County, Kenya. The local population is at considerable risk of coinfection with VL and malaria; however, few studies have described the clinical implications of this comorbidity. Questions remain regarding the immune responses responsible for possible predisposing or protective effects. Moreover, characterisation of environmental and household risk factors for co-acquiring VL and malaria is warranted to increase awareness and guide implementation of targeted control strategies. This protocol intends to address these knowledge gaps concerning VL-malaria coinfections.

METHODS AND ANALYSIS

This observational research project will have a multimethod approach, starting with a cross-sectional study at Kacheliba Sub-County Hospital in West Pokot, Kenya. Patients with laboratory confirmation of a VL and/or malaria infection will be clinically assessed and symptomatology of monoinfections and coinfections will be compared. Second, a questionnaire will be addressed to all included patients and to healthy controls in local communities. This case-control study will aim to describe household and environmental determinants associated with VL-malaria coinfection. Lastly, blood samples will be collected from a small cohort of VL and malaria monoinfected and coinfected patients during treatment of their infection(s), and from healthy controls and asymptomatic VL and malaria cases recruited in local communities. These specimens will be used for serum cytokine measurements and molecular quantitation of Plasmodium and Leishmania. In this way, the immune response and parasite dynamics during VL-malaria coinfection will be characterised longitudinally and compared with those observed in clinical and asymptomatic monoinfections.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the Ethics and Scientific Research Committee of Amref Health Africa. The study findings will be presented at international conferences and published in open-access, peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ISRCTN Registry (ISRCTN15023306).

Establishment of an indicator framework for the transmission risk of the mountain-type zoonotic visceral leishmaniasis based on the Delphi-entropy weight method

BACKGROUND

Visceral leishmaniasis (VL) is one of the most important neglected tropical diseases. Although VL was controlled in several regions of China during the last century, the mountain-type zoonotic visceral leishmaniasis (MT-ZVL) has reemerged in the hilly areas of China in recent decades. The purpose of this study was to construct an indicator framework for assessing the risk of the MT-ZVL in China, and to provide guidance for preventing disease.

METHODS

Based on a literature review and expert interview, a 3-level indicator framework was initially established in November 2021, and 28 experts were selected to perform two rounds of consultation using the Delphi method. The comprehensive weight of the tertiary indicators was determined by the Delphi and the entropy weight methods.

RESULTS

Two rounds of Delphi consultation were conducted. Four primary indicators, 11 secondary indicators, and 35 tertiary indicators were identified. The Delphi-entropy weight method was performed to calculate the comprehensive weight of the tertiary indicators. The normalized weights of the primary indicators were 0.268, 0.261, 0.242, and 0.229, respectively, for biological factors, interventions, environmental factors, and social factors. The normalized weights of the top four secondary indicators were 0.122, 0.120, 0.098, and 0.096, respectively, for climatic features, geographical features, sandflies, and dogs. Among the tertiary indicators, the top four normalized comprehensive weights were the population density of sandflies (0.076), topography (0.057), the population density of dogs, including tethering (0.056), and use of bed nets or other protective measures (0.056).

CONCLUSIONS

An indicator framework of transmission risk assessment for MT-ZVL was established using the Delphi-entropy weight method. The framework provides a practical tool to evaluate transmission risk in endemic areas.

Seroprevalence of visceral leishmaniasis and its associated factors among asymptomatic pastoral community of Dire District, Borena zone, Oromia Region, Ethiopia

Visceral leishmaniasis (VL) is a vector-borne protozoan neglected tropical disease. In some parts of Ethiopia, it is a public health problem and its main causative agent is the Leishmania donovani complex. The objective of the study was to determine the seroprevalence of VL and factors associated among the asymptomatic pastoral community of Dire District, Borena Zone, Oromia Region, Ethiopia. A community-based study was conducted among 432 pastoralist communities from June to July 2021. A systematic random sampling method was used to select households. Pretested structured questionnaires and face-to-face interviews were used to collect data. A single finger-prick blood sample was collected and tested for Leishmania donovani complex using an immune-chromatographic test (rk39-ICT). A logistic regression model was used to assess factors associated with VL infection and a p-value of < 0.05 was considered statistically significant. A total of 432 study participants were included (their mean age was 26.69) and 218 (50.5%) were females. The overall seroprevalence of VL was 33/432(7.6%) (95%CI: 5.32-15.60). Sero-prevalence was significantly associated with high family size (>5) (adjusted odds ratios (AOR) = 5.134; 95% CI: 2.032-9.748), sleeping or/and staying under acacia tree (AOR = 2.984; 95%CI = 1.074-8.288), presence of cracked house walls (AOR = 1.801; 95%CI: 1.026-4.926), presence of termite hills (AOR = 1.938; 95%CL: 1.002-7.050), availability of water points (AOR = 3.893; 95%CI: 1.034-7.426) and presence of domestic animals (AOR = 2.124; 95% CI: 2.341-5.108). It is recommended that community awareness on the transmission and prevention methods of Leishmania donovani complex and taking appropriate interventions on the identified factors play a greater role to prevent and control infection in the area. Further investigation is also needed to characterize the pathogens and risk factors and tackle the problem.

Determinants of anthroponotic cutaneous leishmaniasis by case-control study in Morocco

Leishmaniasis is endemic in Morocco where both cutaneous and visceral forms coexist. To date, anthroponotic cutaneous leishmaniasis (ACL) determinants remain poorly investigated in Morocco. However, the disease risk factors identification is vital to determine the specific preventive process. In this aim, a case-control study was conducted in the main active ACL foci in central Morocco. Epidemiological data were extracted from bulletins, registers and annual reports of the regional direction of Health offices. The socioeconomic and environmental data were collected from epidemiological surveys, completed by a questionnaire intended for accessible positive population and control people selected from the cases' entourage. The study included 258 cases and 395 controls. Our results showed that many socioeconomic factors were associated with ACL in Morocco such as the rural habitation (OR = 4.163; 95% CI: 2.91-5.96), movement to endemic area (OR = 4.53; 95% CI: 3.03-6.77), provenance from leishmaniasis foci (in Essaouira focus OR = 5.34; 95% CI: 1.19-24.03) and poverty. In addition, environmental factors like proximity of vegetation (OR = 2.45; 95% CI: 1.14-5.25), poor domestic hygiene, particularly the absence of sewage system/waste management (OR = 1.63; 95% CI: 1.35-1.96), and presence of animals (OR = 2.67; 95% CI: 1.14-5.25) increase the risk of ACL in Morocco. Except for Matrimonial status (married people, OR = 4.11; 95% CI: 1.80-9.41), there is however no significant association of the disease with the other socio-demographic factors in the study area (p>0.05). These several risk factors must be taken in consideration to prevent this disease through multidisciplinary collaboration and community participation.

Are backyard characteristics relevant factors for the occurrence of human visceral leishmaniasis in Central-Western Brazil?

BACKGROUND

This retrospective case-control study aimed to investigate the factors associated with the occurrence of human visceral leishmaniasis (VL) in the municipality of Rondonópolis, which is a highly endemic area for VL in Central-Western Brazil.

METHODS

All VL cases reported in Rondonópolis from 2011 to 2016 were included. For each case, two neighborhood- and age-matched controls with the absence of past and present history of VL and negative rk39-based immunochromatographic test, were recruited. Data were retrospectively collected through interviews that assessed socioeconomic aspects, housing features, backyard characteristics, presence of animals and daily habits. A multivariate conditional logistic regression analysis was used to identify factors associated with human VL.

RESULTS

During the study period, 81 VL cases were reported in Rondonópolis, of which 37 (45.7%) were included in this study. Seventy controls were also included. The variables associated with VL occurrence were the outdoor location of a bathroom and/or kitchen separated from the rest of the house (OR 7.8; 95% CI 2.1 to 29.5), the presence of a vegetable garden (OR 5.3; 95% CI 1.3 to 21.2) and the presence of decaying fruits (OR 10.7; 95% CI 2.0 to 52.1) in the backyard.

CONCLUSIONS

Our findings suggest an association between backyard characteristics and VL. This may be useful in guiding preventive and control measures against zoonotic VL worldwide.

Prevalence and Risk Factors of Human Leishmaniasis in Ethiopia: A Systematic Review and Meta-Analysis

Introduction

Tropical diseases are public health problems affecting hundreds of millions of people globally. However, the development of adequate, affordable, and accessible treatments is mostly neglected, resulting in significant morbidity and mortality that could otherwise be averted. Leishmaniasis is one of the neglected tropical diseases caused by the obligate intracellular protozoan Leishmania parasite and transmitted by the bite of infected phlebotomine sandflies. No systematic review and meta-analysis has been done to identify the prevalence and risk factors of leishmaniasis to the authors’ knowledge. Therefore, the objective was to determine the prevalence and risk factors of human leishmaniasis in Ethiopia.

Methods

Eleven studies conducted in all regions of Ethiopia, which were fully accessible, written in any language, and original articles done on prevalence and risk factors of leishmaniasis, were included. STATA™ version 11.1 was used for statistical analysis. Chi-square, I², and p values were assessed to check heterogeneity. A random effects model with heterogeneity taken from an inverse-variance model was employed to estimate the pooled effect. Subgroup meta-analysis was computed to reduce random variations among each article’s point prevalence, and Egger and funnel plots were used to check for publication bias.

Results

The highest proportion of human leishmaniasis was reported from a study done in Amhara region (39.1%), and the lowest was reported from a survey done in Tigray (2.3%). The overall pooled prevalence of leishmaniasis was 9.13% (95% CI 5–13.27). Subgroup analysis by region revealed moderate heterogeneity (I² = 51.8%) in studies conducted in the Southern Nations Nationalities and Peoples Region (SNNPR). The presence of hyraxes and being male were associated with an increased risk of human leishmaniasis.

Conclusion

The prevalence of leishmaniasis in Ethiopia remains high (9.13%), with significant risk factors being male and the presence of hyraxes within a 300-m radius of the sleeping area.

Outdoor Residual Insecticide Spraying (ODRS), a New Approach for the Control of the Exophilic Vectors of Human Visceral Leishmaniasis: Phlebotomus orientalis in East Africa

Visceral Leishmaniasis (VL) due to Leishmania donovani is a neglected protozoan parasitic disease in humans, which is usually fatal if untreated. Phlebotomus orientalis, the predominant VL vector in East Africa, is a highly exophilic/exophagic species that poses a major challenge to current Integrated Vector Management (IVM). Here we report results of pilot studies conducted in rural villages in Gedarif state, Sudan, to evaluate outdoor residual spraying of 20mg active ingredient (a.i.) /m² deltamethrin insecticide applied to the characteristic household compound boundary reed fence and to the outside of household buildings (Outdoor Residual Insecticide Spraying, ODRS), and as an alternative, spraying restricted to the boundary fence only (Restricted Outdoor Residual Insecticide Spraying, RODRS). Four to six clusters of 20 households were assigned to insecticide treatments or control in three experiments. Changes in sand fly numbers were monitored over 2,033 trap-nights over 43–76 days follow-up in four sentinel houses per cluster relative to unsprayed control clusters. Sand fly numbers were monitored by sticky traps placed on the ground on the inside (“outdoor”) and the outside (“peridomestic”) of the boundary fence, and by CDC light traps suspended outdoors in the household compound. The effects of ODRS on sand fly numbers inside sleeping huts were monitored by insecticide knockdown. After a single application, ODRS reduced P. orientalis abundance by 83%-99% in outdoor and peridomestic trap locations. ODRS also reduced numbers of P. orientalis found resting inside sleeping huts. RODRS reduced outdoor and peridomestic P. orientalis by 60%-88%. By direct comparison, RODRS was 58%-100% as effective as ODRS depending on the trapping method. These impacts were immediate on intervention and persisted during follow-up, representing a large fraction of the P. orientalis activity season. Relative costs of ODRS and RODRS delivery were $5.76 and $3.48 per household, respectively. The study demonstrates the feasibility and high entomological efficacy of ODRS and RODRS, and the expected low costs relative to current IVM practises. These methods represent novel sand fly vector control tools against predominantly exophilic/exophagic sand fly vectors, aimed to lower VL burdens in Sudan, with potential application in other endemic regions in East Africa.

Phlebotomus orientalis is the predominant vector of visceral leishmaniasis (VL, kala azar) in Sudan and other countries of East Africa, where the disease causes high morbidity and mortality. This sylvatic sand fly species is abundant in wild habitats characterized by presence of black cotton soil and vegetation dominated by Balanites aegyptiaca and/or Acacia seyal trees. In villages, the vector bites people in the household yard and in nearby peri-domestic locations, exhibiting limited indoor resting behaviour. The marked exophagic and exophilic behaviours of P. orientalis represent a profound challenge for VL control by excluding indoor residual spraying of insecticides (IRS) and compromising the efficacy of insecticide-impregnated bednets (ITNs). In this study, we evaluated the entomological efficacy of residual pyrethroid applied outdoors to household boundary fences and the exterior walls of household huts (outdoor residual insecticide spraying, ODRS), to reduce the abundance of P. orientalis inside and outside houses. We also evaluated the entomological impact of a restricted outdoor residual insecticide spraying (RODRS), whereby insecticide was applied only to the boundary fence. The study was carried out in June 2016-June 2017 in Jebel-Algana and Umsalala villages, Gedarif state, eastern Sudan, which are highly endemic for VL. The results showed that a single ODRS application of 20mg a.i. /m² 2.8% deltamethrin provided average reductions of 83%-99% in outdoor and peridomestic P. orientalis sand fly numbers relative to unsprayed control clusters. RODRS reduced outdoor and peridomestic P. orientalis by 60%-88%. The average cost of ODRS and RODRS per household were $5.76 and $3.48, respectively. The costs of these community-based control measures were substantially lower than the costs of LLINs, which is the only evidence-based tool used to protect against VL in the area. Future studies should evaluate the impact of ODRS/RODRS transmission of VL incidence in endemic villages and in seasonal agricultural farms.

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.

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.

Dynamic spatiotemporal modeling of the infected rate of visceral leishmaniasis in human in an endemic area of Amhara regional state, Ethiopia

Visceral Leishmaniasis is a very dangerous form of leishmaniasis and, shorn of appropriate diagnosis and handling, it leads to death and physical disability. Depicting the spatiotemporal pattern of disease is important for disease regulator and deterrence strategies. Spatiotemporal modeling has distended broad veneration in recent years. Spatial and spatiotemporal disease modeling is extensively used for the analysis of registry data and usually articulated in a hierarchical Bayesian framework. In this study, we have developed the hierarchical spatiotemporal Bayesian modeling of the infected rate of Visceral leishmaniasis in Human (VLH). We applied the Stochastics Partial Differential Equation (SPDE) approach for a spatiotemporal hierarchical model for Visceral leishmaniasis in human (VLH) that involves a GF and a state process is associated with an autoregressive order one temporal dynamics and the spatially correlated error term, along with the effect of land shield, metrological, demographic, socio-demographic and geographical covariates in an endemic area of Amhara regional state, Ethiopia. The model encompasses a Gaussian Field (GF), affected by an error term, and a state process described by a first-order autoregressive dynamic model and spatially correlated innovations. A hierarchical model including spatially and temporally correlated errors was fit to the infected rate of Visceral leishmaniasis in human (VLH) weekly data from January 2015 to December 2017 using the R package R-INLA, which allows for Bayesian modeling using the stochastic partial differential equation (SPDE) approach. We found that the mean weekly temperature had a significant positive association with infected rate of VLH. Moreover, net migration rate, clean water coverage, average number of households, population density per square kilometer, average number of persons per household unit, education coverage, health facility coverage, mortality rate, and sex ratio had a significant association with the infected rate of visceral leishmaniasis (VLH) in the region. In this study, we investigated the dynamic spatiotemporal modeling of Visceral leishmaniasis in Human (VLH) through a stochastic partial differential equation approach (SPDE) using integrated nested Laplace approximation (INLA). Our study had confirmed both metrological, demographic, sociodemographic and geographic covariates had a significant association with the infected rate of visceral leishmaniasis (VLH) in the region.

Understanding the economic impact of leishmaniasis on households in endemic countries: a systematic review

INTRODUCTION

Leishmaniasis is a poverty-related disease that causes a significant socioeconomic burden to affected households. Visceral leishmaniasis is fatal if untreated, yet illness costs may lead to delays in accessing care. Skin manifestations of leishmaniasis cause a psychological burden and even longer treatment trajectories. The objective of this review is to evaluate illness costs associated with leishmaniasis across different settings (Asia, Africa, and Latin America) and the consequences to households. Areas covered: Through a systematic review of cost-of-illness studies, we documented the distribution of costs, the health-seeking behavior, and the consequences of leishmaniasis. We discuss the value of cost-of-illness studies for leishmaniasis. Expert commentary: Despite the free provision of diagnostics and treatment in the public health care sector, out-of-pocket payments remain substantial. There has been progress in addressing the economic burden of leishmaniasis, particularly through the elimination initiative in the Indian subcontinent. Though the illness cost is decreasing due to shorter treatment regimens and better access to care, the situation remains challenging in Africa. Improvement of control tools is critical. There is a need to update cost estimates to inform policy-making and ensure sustainable solutions to reduce financial barriers to leishmaniasis care, especially in pursuing universal health coverage.

Changing epidemiology of visceral leishmaniasis in northeastern Brazil: a 25-year follow-up of an urban outbreak

Background

Visceral leishmaniasis (VL) continues to be a deadly parasitic disease in Brazil but the epidemiology has changed. The objective of this study was to assess the evolution of urban VL in the city of Natal, Brazil, over the past 25 y.

Methods

A retrospective study of human VL was performed, considering reported cases over the past 25 y in Natal. Analyses considered the spatial distribution of VL cases, human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) co-infection, Leishmania infantum infection in dogs, density of the insect vector (Lutzomyia longipalpis) and socio-economic factors.

Results

Paralleling migration of the population, VL cases changed from mostly rural to predominantly urban regions. The incidence of human VL was highest during the initial years (1990-1994) of our study. Human VL was positively associated with a high density of L. longipalpis, a high prevalence of canine L. infantum infection and HIV/AIDS co-infection. The average age at diagnosis increased over prior years and males were more frequently affected. The overall fatality rate was 6%. Socio-economic variables indicative of poverty were associated with a greater incidence of VL and clusters of VL.

Conclusion

VL has become endemic in Natal. The disease is associated with poverty and male gender. Surprisingly, there has been an increase in the age at diagnosis.

A fine scale eco-epidemiological study on endemic visceral leishmaniasis in north ethiopian villages

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We conducted fine-scale eco-epidemiological analyses of factors associated with visceral leishmaniasis transmission.

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The population densities of Phlebotomus orientalis, the vector, were negatively correlated with distance from vertisols.

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Sero-positivity to Ph. orientalis saliva, was found in people living close to vertisol areas.

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Apparent clustering of infections indicates that transmission occurs around houses located close to vertisols.

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Our data suggest that asymptomatic individuals serve as reservoir hosts for anthroponotic transmission inside villages.

Visceral Leishmaniasis (VL) is a disseminated protozoan infection caused by Leishmania donovani that affects almost half a million people annually. In Northern Ethiopia, VL is common in migrant agricultural laborers returning from the lowland sesame fields of Metema and Humera. Recent VL foci have emerged in resident rural populations near the town. In the current study, we evaluate multilevel entomological, epidemiological and ecological factors associated with infection and disease through fine-scale eco-epidemiological analyses in three villages. Satellite images showed that villages constructed in or close to vertisols, were likely to become endemic for VL. Vertisols or black-cotton soil, are characterized by high contents of smectitic clay minerals, which swell when hydrated and shrink upon desiccation, causing extensive deep cracking during the dry season. The population densities of Phlebotomus orientalis, the vector, were negatively correlated with distance from vertisols and persons living close to vertisols were more likely to be bitten by sand flies, as evidenced by sero-positivity to Ph. orientalis saliva. Apparent (albeit non-significant) clustering of VL cases and abundant asymptomatic infections close to vertisols, suggest anthroponotic transmission around houses located close to vertisols. Comparable rates of male and female volunteers, mostly under 15 years of age, were infected with L. donovani but a significantly higher proportion of males succumbed to VL indicating a physiological gender-linked male susceptibility. Our data suggest that the abundant infected persons with high parasitemias who remain asymptomatic, may serve as reservoir hosts for anthroponotic transmission inside villages. Only limited insights on the transmission dynamics of L. donovani were gained by the study of environmental factors such as presence of animals, house structure and vegetation cover.

Changing demographics of visceral leishmaniasis in northeast Brazil: Lessons for the future

Background

Visceral leishmaniasis (VL) caused by Leishmania infantum became a disease of urban areas in Brazil in the last 30 years and there has been an increase in asymptomatic L. infantum infection with these areas.

Methodology/Principal findings

A retrospective study of human VL was performed in the state of Rio Grande do Norte, Brazil, for the period of 1990–2014. The data were divided into five-time periods. For all VL cases, data on sex, age, nutritional status and childhood vaccination were collected. Geographic information system tools and statistical models were used to analyze the dispersion of human VL. The mean annual incidence of VL was 4.6 cases/100,000 inhabitants, with total 3,252 cases reported. The lethality rate was 6.4%. Over time the annual incidence of VL decreased in the 0–4 years (p<0.0001) and 5–9 (p <0.0001) age groups, but increased in ages 20–39 (p<0.001) and >40 years (p<0.0001). VL occurred more often in males (β₂ = 2.5; p<0.0001). The decreased incidence of VL in children was associated with improved nutritional status and childhood immunizations including measles, poliomyelitis, BCG, and hepatitis B. Human VL correlated temporally and geographically with canine L. infantum infection (p = 0.002, R² = 0.438), with rainfall and with Lutzomyia longipalpis density (r = 0.762). Overall, the incidence of VL decreased, while VL-AIDS increased, especially between 2010–2014. VL was more frequently found in areas that lacked urban infrastructure, detected by lack of garbage collection and sewers, whereas HIV infection was associated with higher levels of schooling and evidence of higher socioeconomic status.

Conclusion/Significance

The demographics of VL in northeastern Brazil have changed. Disease incidence has decreased in children and increased in adults. They were associated with improvements in nutrition, socioeconomic status and immunization rates. Concurrent VL-AIDS poses a serious challenge for the future.

We studied factors associated with the changing demographics of visceral leishmaniasis (VL) in Northeast Brazil, including environmental and socioeconomic determinants of disease, during the period 1990 to 2014. The incidence of VL was higher in urban areas, and regions with higher levels of canine L. infantum infection. Human males were more commonly affected than females. The incidence of VL in children under age 10 decreased during the period of study, simultaneous with increased incidence in adults. Reduction in the VL incidence among children was associated with improved socioeconomic status, administration of childhood vaccines and better nutritional status. Geographic areas with higher rainfall had higher densities of Lu. longipalpis, the primary vector of L. infantum in Brazil. VL was more frequently found in areas with indicators of poverty including sparse garbage collection and lack of urban infrastructure. During the past 25 years, HIV/AIDS has spread to areas where VL is endemic and has contributed to an increased incidence of VL-AIDS co-infection in adults.

"Kala-Azar is a Dishonest Disease": Community Perspectives on Access Barriers to Visceral Leishmaniasis (Kala-Azar) Diagnosis and Care in Southern Gadarif, Sudan

Early diagnosis and treatment is the principal strategy to control visceral leishmaniasis (VL), or kala-azar in East Africa. As VL strikes remote rural, sparsely populated areas, kala-azar care might not be accessed optimally or timely. We conducted a qualitative study to explore access barriers in a longstanding kala-azar endemic area in southern Gadarif, Sudan. Former kala-azar patients or caretakers, community leaders, and health-care providers were purposively sampled and thematic data analysis was used. Our study participants revealed the multitude of difficulties faced when seeking care. The disease is well known in the area, yet misconceptions about causes and transmission persist. The care-seeking itineraries were not always straightforward: “shopping around” for treatments are common, partly linked to difficulties in diagnosing kala-azar. Kala-azar is perceived to be “hiding,” requiring multiple tests and other diseases must be treated first. Negative perceptions on quality of care in the public hospitals prevail, with the unavailability of drugs or staff as the main concern. Delay to seek care remains predominantly linked to economic constraint: albeit treatment is for free, patients have to pay out of pocket for everything else, pushing families further into poverty. Despite increased efforts to tackle the disease over the years, access to quality kala-azar care in this rural Sudanese context remains problematic. The barriers explored in this study are a compelling reminder of the need to boost efforts to address these barriers.

A review of visceral leishmaniasis during the conflict in South Sudan and the consequences for East African countries

Background

Visceral leishmaniasis (VL), caused predominantly by Leishmania donovani and transmitted by both Phlebotomus orientalis and Phlebotomus martini, is highly endemic in East Africa where approximately 30 thousands VL cases are reported annually. The largest numbers of cases are found in Sudan - where Phlebotomus orientalis proliferate in Acacia forests especially on Sudan’s eastern border with Ethiopia, followed by South Sudan, Ethiopia, Somalia, Kenya and Uganda. Long-standing civil war and unrest is a dominant determinant of VL in East African countries. Here we attempt to identify the correlation between VL epidemics and civil unrest.

Objective and methodology

In this review, literature published between 1955 and 2016 have been gathered from MSF, UNICEF, OCHA, UNHCR, PubMed and Google Scholar to analyse the correlation between conflict and human suffering from VL, which is especially apparent in South Sudan.

Findings

Waves of forced migration as a consequence of civil wars between 1983 and 2005 have resulted in massive and lethal epidemics in southern Sudan. Following a comprehensive peace agreement, but especially with increased allocation of resources for disease treatment and prevention in 2011, cases of VL declined reaching the lowest levels after South Sudan declared independence. However, in the latest epidemic that began in 2014 after the onset of a civil war in South Sudan, more than 1.5 million displaced refugees have migrated internally to states highly endemic for VL, while 800,000 have fled to neighboring countries.

Conclusion

We find a strong relationship between civil unrest and VL epidemics which tend to occur among immunologically naïve migrants entering VL-endemic areas and when Leishmania-infected individuals migrate to new areas and establish additional foci of disease. Further complicating factors in East Africa’s VL epidemics include severe lack of access to diagnosis and treatment, HIV/AIDS co-infection, food insecurity and malnutrition. Moreover, cases of post-kala-azar dermal leishmaniasis (PKDL) can serve as important reservoirs of anthroponotic Leishmania parasites.