Housing Characteristics and Leishmaniasis: A Systematic Review

Better floors, better health: a theory of change for an improved household flooring intervention in rural communities in Kwale and Bungoma counties, Kenya

BACKGROUND

Household flooring is increasingly being investigated as a determinant of health, however the pathways through which flooring may impact health and wellbeing are not yet well understood. The SABABU study is a cluster-randomised controlled trial evaluating the impact of an improved flooring intervention on soil-transmitted helminthiasis, tungiasis, and enteric infections in Bungoma and Kwale counties, Kenya. This paper presents the findings from a theory of change development process that was undertaken as part of the formative research phase of the SABABU project.

METHODS

A co-creation workshop (n = 1), stakeholder meetings (n = 2), and community meetings (n = 2) were held with a range of participants including community members (n = 36), village-level leaders (n = 28), and local government stakeholders (n = 14) to draft and refine the theory of change framework. These meetings were informed by a previous formative research phase conducted in study communities - comprised of household observations, in-depth interviews, and focus group discussions with community members - to investigate daily routines, use of space within homes, and attitudes towards home improvement.

RESULTS

The theory of change framework demonstrates how the improved household flooring intervention aims to reduce prevalence of soil-transmitted helminthiasis, enteric infections and tungiasis and improve psychological wellbeing among children and caregivers. Reductions in infections are predicated on limited contact between improved floors and animals, regular floor cleaning, and household members conducting their daily routines on the new floors. Gains in psychological wellbeing are tied to increased feelings of pride, self-efficacy, and social progress, as well as improved quality of life through reduced morbidity from enteric and parasitic infections.

CONCLUSION

This study presents a theory of change framework mapping the pathways through which an improved flooring intervention may impact health and wellbeing. The results can be of use to researchers or programmes that are in the design or evaluation phase of a household flooring project in Kenya or other settings where access to improved floors is limited.

An updated systematic review with meta-analysis and meta-regression of the factors associated with human visceral leishmaniasis in the Americas

BACKGROUND

Human visceral leishmaniasis (VL) is a systemic disease with high case-fatality rates and a widespread distribution. Continuous evaluation of the risk factors for VL is essential to ensure the effective implementation of prevention and control measures. The present study reviews the factors associated with VL in the Americas.

METHODS

This systematic review updates a previous 2013 report by including cross-sectional, cohort and case-control studies published between July 2011 and April 2024. Associations between VL and risk factors were analyzed using random-effects meta-analysis, subgroup analysis, and meta-regression models. Studies were classified according to level of evidence using the GRADE approach and the evolution in the quality of investigations was assessed.

RESULTS

Forty-six studies were included in the review and 21 variables were evaluated in the meta-analyses. Combination of all study types revealed that men had greater chances of VL than women, but the association was strong and significant only in case-control studies. Although higher chances of VL in children and in households with dogs or chickens/other fowl were identified in case-control studies, an inverse association was observed in cross-sectional and cohort studies. Higher chances of VL were associated with poor economic/living conditions, individuals living in domiciles with backyards or with seropositive dogs, and individuals with prior contact with infected household members/relatives/neighbors. The level of evidence for associations of VL with sex and age was classified as moderate whilst that for all other associations was either low or very low. The methodological quality of recent studies showed a positive progression but shortcomings were still evident regarding selection criteria and methods of data analysis.

CONCLUSION

While there is a higher incidence of symptomatic VL among men and children, the likelihood of infection is similar between the groups. There is insufficient evidence to support the claim that the presence of dogs or fowl at the domicile increases the chances of VL. However, socioeconomic and living conditions, as well as previous occurrence of human and canine VL, are influential factors. Future research should be conducted with greater statistical power and using molecular diagnostic techniques, preferably involving cohort studies in diverse Latin American countries.

Spatial variation in housing construction material in low- and middle-income countries: A Bayesian spatial prediction model of a key infectious diseases risk factor and social determinant of health

Housing infrastructure and quality is a major determinant of infectious disease risk and other health outcomes in regions where vector borne, waterborne and neglected tropical diseases are endemic. It is important to quantify the geographical distribution of improvements to dwelling components to identify and target resources towards populations at risk. This study aimed to model the sub-national spatial variation in housing materials using covariates with quasi-global coverage and use the resulting estimates to map predicted coverage across the world's low- and middle-income countries. Data on materials used in dwelling construction were sourced from nationally representative household surveys conducted since 2005. Materials used for construction of flooring, walls, and roofs were reclassified as improved or unimproved. Households lacking location information were georeferenced using a novel methodology. Environmental and demographic spatial covariates were extracted at those locations for use as model predictors. Integrated nested Laplace approximation models were fitted to obtain, and map predicted probabilities for each dwelling component. The dataset compiled included information from households in 283,000 clusters from 350 surveys. Low coverage of improved housing was predicted across the Sahel and southern Sahara regions of Africa, much of inland Amazonia, and areas of the Tibetan plateau. Coverage of improved roofs and walls was high in the Central Asia, East Asia and Pacific and Latin America and the Caribbean regions. Improvements in all three components, but most notably floors, was low in Sub-Saharan Africa. The strongest determinants of dwelling component quality related to urbanization and economic development, suggesting that programs should focus on supply-side interventions, providing resources for housing improvements directly to the populations that need them. These findings are made available to researchers as files that can be imported into a GIS for integration into relevant analyses to derive improved estimates of preventable health burdens attributed to housing.

Environmental Risk Factors for Visceral Leishmaniasis: An Analysis of Housing Types and Behavioral Factors in Baringo County, Kenya

Visceral leishmaniasis (VL) is endemic in Baringo County, Kenya, and contributes significantly to the burden of disease in the region. Housing structures and other environmental risk factors contribute to transmission dynamics, but these have not been specifically studied in Baringo. The aim of this study was to increase understanding of VL transmission in the region through determining relationships between VL infection, housing, and other environmental factors. Data collection occurred from February 1 to May 31, 2023 at Chemolingot Sub-County Hospital and patients' homesteads via questionnaires of primary VL patients being treated and VL follow-up patients who were still residing in the same house as when the infection occurred. Factors assessed were housing structures, proximity to vector breeding and resting sites, and prevention and control measure practices. A baseline assessment of housing types was conducted through direct ethnographic observation and used in the analysis. Forty-one patients were included in the study. A χ2 analysis and Fisher's test were used to determine association between VL infection and housing materials, where VL patient housing data were compared with the regional baseline assessment. Significant associations with VL infection were found between mud and stick walls (P <0.001); mud walls (P <0.001); mud, stick, and grass combination walls (P = 0.02); and stick and grass walls (P <0.001). Behavior comparison showed that most VL-protective behaviors were practiced by follow-up patients after infection. Results showed an increased need for VL prevention focusing on environmental factors.

An update on Leishmania martiniquensis infections: Transmission, clinical characteristics, and treatment

Leishmaniasis, caused by intracellular protozoa of the Leishmania genus, continues to be a global health issue, with approximately 700,000 to 1 million new cases occur annually worldwide. The disease is transmitted via the bite of infected female sand flies of the genus Phlebotomus, resulting in a range of symptoms known as cutaneous, mucocutaneous, and visceral leishmaniasis. The species Leishmania (Mundinia) martiniquensis, discovered in 1995, has been linked to cases in individuals with HIV, presenting with diverse clinical pictures. Interestingly, biting midges, not sandflies, has proved to serve as its potentially biological vector. This study focuses on understanding the transmission, clinical aspects, and effective treatment of L. martiniquensis infections. A comprehensive search strategy was employed to identify relevant published papers on the epidemiology, transmission, clinical characteristics, and treatment of L. martiniquensis up to August 2024. The clinical manifestations encompass localized cutaneous leishmaniasis, disseminated cutaneous leishmaniasis, mucocutaneous leishmaniasis, and visceral leishmaniasis. Leishmaniasis is associated with comorbidities such as inadequate nutrition, population displacement, and reduced immunity. Risk factors for Leishmania infection include the presence of domestic animals, age, gender, and environmental factors. Amphotericin B deoxycholate (AmB) is the main treatment. Combination therapy with allicin and andrographolide may reduce AmB side effects. Recent research investigates other treatments including 8-hydroxyquinoline, which works synergistically with AmB against L. martiniquensis.

Effect of indoor residual spraying on sandfly abundance and incidence of visceral leishmaniasis in India, 2016-22: an interrupted time-series analysis and modelling study

BACKGROUND

Efforts to eliminate visceral leishmaniasis in India mainly consist of early detection and treatment of cases and indoor residual spraying with insecticides to kill the phlebotomine sandfly Phlebotomus argentipes that transmits the causative Leishmania protozoa. In this modelling study, we aimed to estimate the effect of indoor residual spraying (IRS) on vector abundance and transmission of visceral leishmaniasis in India.

METHODS

In this time-series analysis and modelling study, we assessed the effect of IRS on vector abundance by using indoor vector-abundance data (from 2016 to 2022) and IRS quality-assurance data (from 2017-20) from 50 villages in eight endemic blocks in India where IRS was implemented programmatically. To assess a potential dose-response relation between insecticide concentrations and changes in sandfly abundance, we examined the correlation between site-level insecticide concentrations and the site-level data for monthly sandfly abundances. We used mathematical modelling to link vector data to visceral leishmaniasis case numbers from the national Kala-Azar Management Information System registry (2013-21), and to predict the effect of IRS on numbers of averted cases and deaths.

FINDINGS

IRS was estimated to reduce indoor sandfly abundance by 27% (95% CI 20-34). Concentrations of insecticides on walls were significantly-but weakly-associated with the degree of reduction in vector abundance, with a reduction of -0·0023 (95% CI -0·0040 to -0·0007) sandflies per mg/m2 insecticide (p=0·0057). Reported case numbers of visceral leishmaniasis were well explained by trends in vector abundance. Village-wide IRS in response to a newly detected case of visceral leishmaniasis was predicted to reduce disease incidence by 6-40% depending on the presumed reduction in vector abundance modelled.

INTERPRETATION

Indoor residual spraying has substantially reduced sandfly abundance in India, which has contributed to reductions in visceral leishmaniasis and related deaths. To prevent the re-emergence of visceral leishmaniasis as a public health problem, surveillance of transmission and sandfly abundance is warranted.

FUNDING

Bill & Melinda Gates Foundation.

TRANSLATION

For the Hindi translation of the abstract see Supplementary Materials section.

Asymptomatic Leishmania Infection among Blood Donors in a Southern Province of Thailand

Leishmaniasis poses significant public health challenges in endemic regions. Understanding the prevalence of asymptomatic Leishmania infection and identifying risk factors among blood donors is crucial. This study addressed a knowledge gap by evaluating the prevalence of asymptomatic Leishmania infection and pinpointing associated risk factors among blood donors in an endemic area in Thailand and aimed to enhance blood donation safety protocols and reduce the risk of transfusion-transmitted Leishmania infection. A cross-sectional study and a longitudinal follow-up were conducted among 500 blood donors in Trang Province, southern Thailand. A serological test was performed using the direct agglutination test (DAT), and DNA detection was performed using nested polymerase chain reaction (nPCR) to screen for Leishmania infection. Potential risk factors associated with the infection were also assessed. The study identified a 19.0% prevalence of asymptomatic Leishmania infection among blood donors, with nPCR proving more effective in detecting infections (13.0%) than DAT (6.4%). Notably, Leishmania martiniquensis was the predominant species identified, highlighting the local epidemiological profile of Leishmania infection. Furthermore, using multivariate analysis, living in stilt houses was independently associated with Leishmania infection (adjusted odds ratio = 1.85; 95% CI = 1.04-3.28; P = 0.035). A high prevalence of asymptomatic Leishmania infection among blood donors underscores the need for integrating comprehensive Leishmania screening protocols into blood donation processes, particularly in endemic regions. It advocates for using molecular diagnostics to enhance detection accuracy. Furthermore, living in stilt houses as a risk factor emphasizes the importance of environmental management in leishmaniasis control efforts.

Portable smartphone-based molecular test for rapid detection of Leishmania spp

PURPOSE

Leishmaniasis, caused by the parasite of the genus Leishmania, is a neglected tropical disease which is endemic in more than 60 countries. In South-East Asia, Brazil, and East Africa, it mainly occurs as kala-azar (visceral leishmaniasis, VL), and subsequently as post kala-azar dermal leishmaniasis (PKDL) in a smaller portion of cases. As stated per WHO roadmap, accessibility to accurate diagnostic methods is an essential step to achieve elimination. This study aimed to test the accuracy of a portable minoo device, a small battery-driven, multi-use fluorimeter operating with isothermal technology for molecular diagnosis of VL and PKDL.

METHODS

Fluorescence data measured by the device within 20 min are reported back to the mobile application (or app) via Bluetooth and onward via the internet to a backend. This allows anonymous analysis and storage of the test data. The test result is immediately returned to the app displaying it to the user.

RESULTS

The limit of detection was 11.2 genome copies (95% CI) as determined by screening a tenfold dilution range of whole Leishmania donovani genomes using isothermal recombinase polymerase amplification (RPA). Pathogens considered for differential diagnosis were tested and no cross-reactivity was observed. For its diagnostic performance, DNA extracted from 170 VL and PKDL cases, comprising peripheral blood samples (VL, n = 96) and skin biopsies (PKDL, n = 74) from India (n = 108) and Bangladesh (n = 62), was screened. Clinical sensitivity and specificity were 88% and 91%, respectively.

CONCLUSION

Minoo devices can offer a convenient, cheaper alternative to other molecular diagnostics. Its easy handling makes it ideal for use in low-resource settings to identify parasite burden.

Human Cutaneous Leishmaniasis in North Africa and Its Threats to Public Health: A Statistical Study Focused on Djelfa (Algeria)

Cutaneous leishmaniasis, the most common form of leishmaniasis, causes long-term skin lesions on exposed areas of the skin. It is caused by a protozoan parasite belonging to the genus Leishmania and is transmitted via infected phlebotomine sand flies. In North Africa, particularly Algeria, the disease represents a major public health problem. This retrospective study, which focuses on the agropastoral region of Djelfa (central Algeria) during a period of 16 years, from 2006 to 2021, is part of the surveillance of cutaneous leishmaniasis to identify the key factors favouring its probable spread. The analyzed data reveal that this disease is more prevalent in male patients (53.60%) and is highly widespread in this vast area of 66,415 km2 with a total of 3864 CL cases, reaching a peak of 1407 cases in 2006. Statistically, the Pearson correlation validated by the p-value shows, in an original and sometimes unexpected way, that certain factors, such as temperature linked to climate change, are playing a significant role in the probable spread of the disease in Djelfa and its surrounding regions. The concentration of the population in some specific rural areas with limited or nonexistent access to public health services is another potential factor in disease transmission. The results were highlighted by a significant correlation coefficient (r=0.66) with a p-value less than 0.01. While there is currently no vaccine or prophylactic drug available, our research represents a preliminary approach that addresses various epidemiological aspects of the disease. This paves the way for a proactive preventive strategy involving the control of vector-borne diseases.

Environmental health risk factors and cutaneous leishmaniasis (CL): A case-control study in northeastern Iran

Background & objectives

Cutaneous leishmaniasis (CL) is one of the main causes of vector-born diseases in younger population. To evaluate the association of environmental health factors on the odds of CL incidence, a case-control study was conducted in northeastern Iran.

Methods

This study was conducted within 2020-2021 based on individual and household data from a tertiary referral center. Cases were patients diagnosed with CL by PCR method; controls were selected among the patients' relatives, and information was obtained from a health registry system. Demographic and socioeconomic data of 1871 subjects, included age, sex, household information and environmental health factors. Multivariable models with environmental factors in various conditions and CL were separately fit by univariate and mixed multiple unconditional logistic regression.

Results

Participants included 617 cases (mean [SD] age, 13.62[13.72] years; 58.20% male) and 1264 controls (mean [SD] age, 16.45[15.44] years; 50.40% male). Results revealed that the use of well-water sources compared to surface water is significantly associated with CL (odds ratio [OR]=0.204; 95%CI, 0.13-0.33;P<0.001). Muddy houses, ruined buildings or wastelands and stagnant water, canals and rivers near the houses were also associated with CL (OR=3.85; 95%CI, 1.66-8.89; P=.002; OR=2.47; 95%CI, 1.76-3.47; P<.001). Besides, existence of pine tree was found to be a risk factor (OR=3.25; 95%CI, 2.12-4.99; P<.001) and similarly for the use of waste collection system (OR=4.43; 95%CI, 3.32-7.51; P<.001).

Interpretation & conclusion

Environmental factors related to houses were significantly associated with CL and may represent the modifiable risk factors of CL disease.

Comparison of collection methods for Phlebotomus argentipes sand flies to use in a molecular xenomonitoring system for the surveillance of visceral leishmaniasis

BACKGROUND

The kala-azar elimination programme has resulted in a significant reduction in visceral leishmaniasis (VL) cases across the Indian Subcontinent. To detect any resurgence of transmission, a sensitive cost-effective surveillance system is required. Molecular xenomonitoring (MX), detection of pathogen DNA/RNA in vectors, provides a proxy of human infection in the lymphatic filariasis elimination programme. To determine whether MX can be used for VL surveillance in a low transmission setting, large numbers of the sand fly vector Phlebotomus argentipes are required. This study will determine the best method for capturing P. argentipes females for MX.

METHODOLOGY/PRINCIPAL FINDINGS

The field study was performed in two programmatic and two non-programmatic villages in Bihar, India. A total of 48 households (12/village) were recruited. Centers for Disease Control and Prevention light traps (CDC-LTs) were compared with Improved Prokopack (PKP) and mechanical vacuum aspirators (MVA) using standardised methods. Four 12x12 Latin squares, 576 collections, were attempted (12/house, 144/village,192/method). Molecular analyses of collections were conducted to confirm identification of P. argentipes and to detect human and Leishmania DNA. Operational factors, such as time burden, acceptance to householders and RNA preservation, were also considered. A total of 562 collections (97.7%) were completed with 6,809 sand flies captured. Females comprised 49.0% of captures, of which 1,934 (57.9%) were identified as P. argentipes. CDC-LTs collected 4.04 times more P. argentipes females than MVA and 3.62 times more than PKP (p<0.0001 for each). Of 21,735 mosquitoes in the same collections, no significant differences between collection methods were observed. CDC-LTs took less time to install and collect than to perform aspirations and their greater yield compensated for increased sorting time. No significant differences in Leishmania RNA detection and quantitation between methods were observed in experimentally infected sand flies maintained in conditions simulating field conditions. CDC-LTs were favoured by householders.

CONCLUSIONS/SIGNIFICANCE

CDC-LTs are the most useful collection tool of those tested for MX surveillance since they collected higher numbers of P. argentipes females without compromising mosquito captures or the preservation of RNA. However, capture rates are still low.

Distribution and Risk of Cutaneous Leishmaniasis in Khyber Pakhtunkhwa, Pakistan

Cutaneous leishmaniasis (CL) is a zoonotic infection caused by obligate intracellular protozoa of the genus Leishmania. This study aimed to investigate CL in Khyber Pakhtunkhwa, Pakistan and to estimate the risk of epidemics. Clinico-epidemiological data of 3188 CL patients were collected from health facilities in 2021. Risk factors were analyzed using the chi-square test. ArcGIS V.10.7.1 was applied for spatial analysis. The association between CL occurrence and climatic variables was examined by Bayesian geostatistical analysis. The clinical data revealed males or individuals younger than 20 years old were more affected. Most patients presented with a single lesion, and the face was the most attacked body part. CL was prevalent in the southern region in winter. A proportional symbol map, a choropleth map, and a digital elevation model map were built to show the distribution of CL. Focal transmission was predicted by inverse distance weighting interpolation. Cluster and outlier analysis identified clusters in Bannu, Dir Lower, and Mardan, and hotspot analysis suggested Bannu as a high-risk foci. Bayesian geostatistical analysis indicated that increasing precipitation and temperature as well as low altitudes were associated with CL infection. The study has provided important information for public health sectors to develop intervention strategies for future CL epidemics.

Evidence map of diagnosis, treatment, prognosis, prevention, and control in visceral leishmaniasis

Objective

To develop an evidence map on visceral leishmaniasis prevention, control, diagnosis, treatment, and prognosis.

Methods

Systematic reviews on visceral leishmaniasis were searched using MEDLINE/PubMed and Virtual Health Library. After selection, each included systematic review was assessed, characterized, and categorized by intervention type and by outcomes, according to the methodology offered by the PAHO/WHO Latin American and Caribbean Center on Health Sciences Information (BIREME). The methodological quality was assessed using the AMSTAR2 tool to determine the confidence level of the evidence obtained.

Results

Among the prevention and control interventions, insecticide spraying, bednets, dog collars, and dog culling were the most assessed, emphasizing that insecticidal dog collars can reduce visceral leishmaniasis incidence in dogs. Regarding diagnosis, polymerase chain reaction (PCR), rK39 immunochromatographic test (rK39 ICT), and direct agglutination test (DAT) presented high sensitivity and specificity. As for treatment, pentavalent antimonials and amphotericin B were the most analyzed drugs and showed therapeutic success; however, serious adverse events can occur due to their use. The prognostic factors identified were anemia, edema, bleeding, jaundice, age, and HIV coinfection.

Conclusions

The evidence map developed shows rK39 ICT and DAT as promising diagnostic alternatives and reinforces the efficacy of liposomal amphotericin B and pentavalent antimonials. Insecticide-impregnated dog collars appear as a promising measure for the control of visceral leishmaniasis, but there is also a need for future studies and reviews with higher methodological quality, especially on prevention and control interventions.

Magnitude of visceral leishmaniasis and HIV coinfection and association with social determinants of health in the Northeast region of Brazil: a retrospective, spatiotemporal model (2010-2018)

The Northeast region of Brazil (NRB) includes the states with the highest prevalence of visceral leishmaniasis (VL), as well as those with significant increases in HIV cases. This study aims to analyze the spatiotemporal patterns of VL-HIV coinfection and its association with the social determinants of health (SDH) in the NRB. Time trend analysis and Bayesian spatial statistical inferences, Moran's autocorrelation, and retrospective space-time scanning were performed. Spatial regression modelling was used to build an explanatory model for the occurrence of VL-HIV coinfection within NRB. A total of 1550 cases of VL-HIV coinfection were confirmed. We observed a higher prevalence among males (1232; 83%), individuals aged from 20 to 59 years (850; 54.8%), non-white skin color (1,422; 91.7%), and with low education (550; 35.48%). NRB showed an increasing and significant trend in the detection rate of coinfection (APC, 5.3; 95% CI, 1.4 to 9.4). The states of Maranhão and Piauí comprised the high-risk cluster. The SDH that most correlated with the occurrence of coinfection were poor housing, low income, and low education. VL-HIV is dispersed in the NRB but chiefly affects states with greater social vulnerability. Taken together, these findings reinforce the necessity to implement surveillance strategies that will contribute to the reduction of cases in these populations.

New phosphoramidates containing selenium as leishmanicidal agents

This work reports the synthesis, characterization by FTIR, ¹H, ¹³C and ⁷⁹Se NMR, mass spectrometry and elemental analysis techniques as well as the in vitro evaluation of the leishmanicidal activity of thirteen new selenophosphoramidate derivatives. Among the new compounds, four of them (compounds 1f, 1g, 2f and 2g), which exhibited the best profile, were tested against infected macrophages and were selected for further studies related their leishmanicidal mechanism. In this regard, trypanothione redox-system alteration was determined. Compound 1g, under similar conditions, was more effective than the corresponding references. In addition, theoretical calculations showed that this compound also presents most physico-chemical and pharmacokinetic properties within the ranges expected for orally available drugs. It is believed that selenophophoramidate functionalities may represent a scaffold to be explored toward the development of new agents for leishmania treatment.

Prevalence and associated risk factors of Leishmania infection among immunocompetent hosts, a community-based study in Chiang Rai, Thailand

Background

Leishmaniasis is an emerging infectious disease reported in the north and south of Thailand of which patients with HIV/AIDS are a high risk group for acquiring the infection. A lack of information regarding prevalence, and the risk association of Leishmania infection among asymptomatic immunocompetent hosts needs further investigation. Information on potential vectors and animal reservoirs in the affected areas is also important to control disease transmission.

Methods

An outbreak investigation and a cross-sectional study were conducted following one index case of cutaneous leishmaniasis (CL) caused by L. martiniquensis in an immunocompetent male patient reported in August 2015, Chiang Rai Province, Thailand. From September to November 2015, a total of 392 participants at two study areas who were related to the index case, 130 students at a semi-boarding vocational school and 262 hill tribe villagers in the patient’s hometown, were recruited in this study. The nested internal transcribed spacer 1-PCR (ITS1-PCR) was performed to detect Leishmania DNA in buffy coat, and nucleotide sequencing was used to identify species. Antibody screening in plasma was performed using the Direct Agglutination Test (DAT), and associated risk factors were analyzed using a standardized questionnaire. Captured sandflies within the study areas were identified and detected for Leishmania DNA using nested ITS1-PCR. Moreover, the animal reservoirs in the study areas were also explored for Leishmania infection.

Results

Of 392 participants, 28 (7.1%) were positive for Leishmania infection of which 1 (4.8%) was L. martiniquensis, 12 (57.1%) were L. orientalis and 8 (38.1%) were Leishmania spp. Of 28, 15 (53.6%) were DAT positive. None showed any symptoms of CL or visceral leishmaniasis. Risk factors were associated with being female (adjusted odds ratio, AOR 2.52, 95%CI 1.01–6.26), increasing age (AOR 1.05, 95%CI 1.02–1.08), having an animal enclosure in a housing area (AOR 3.04, 95%CI 1.13–8.22), being exposed to termite mounds (AOR 3.74, 95%CI 1.11–12.58) and having domestic animals in a housing area (AOR 7.11, 95%CI 2.08–24.37). At the semi-boarding vocational school, six Sergentomyia gemmea samples were PCR positive for DNA of L. orientalis and one S. gemmea was PCR positive for DNA of L. donovani/L. infantum. Additionally, one Phlebotomus stantoni was PCR positive for DNA of L. martiniquensis, and one black rat (Rattus rattus) was PCR positive for DNA of L. martiniquensis.

Conclusion

This information could be useful for monitoring Leishmania infection among immunocompetent hosts in affected areas and also setting up strategies for prevention and control. A follow-up study of asymptomatic individuals with seropositive results as well as those with positive PCR results is recommended.

This is the first community-based study investigating the prevalence and associated risk factors of Leishmania infection among immunocompetent individuals, demonstrating the situation of Leishmania infection in endemic areas of Thailand. An outbreak investigation and a cross-sectional study were conducted following one index case of cutaneous leishmaniasis (CL) caused by L. martiniquensis in an immunocompetent male patient reported in August 2015, Chiang Rai Province, Thailand. Of 392 participants, 28 (7.1%) were positive for Leishmania infection of which 1 (4.8%) was L. martiniquensis, 12 (57.1%) were L. orientalis and 8 (38.1%) were Leishmania spp. The factors associated with Leishmania infection included being female, increasing age, having an animal enclosure in a housing area, being exposed to termite mounds and having domestic animals in a housing area. This information revealed the first burden and risk factors of Leishmania infection among immunocompetent individuals in Thailand and highlighted the urgent need for effective interventions to prevent and control the disease in high risk populations in endemic areas.

Effectiveness of vector control methods for the control of cutaneous and visceral leishmaniasis: A meta-review

Elimination of visceral leishmaniasis (VL) in Southeast Asia and global control of cutaneous leishmaniasis (CL) and VL are priorities of the World Health Organization (WHO). But is the existing evidence good enough for public health recommendations? This meta-review summarises the available and new evidence for vector control with the aims of establishing what is known about the value of vector control for the control of CL and VL, establishing gaps in knowledge, and particularly focusing on key recommendations for further scientific work. This meta-review follows the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) criteria, including (1) systematic reviews and meta-analyses (SRs/MAs) for (2) vector control methods and strategies and (3) for the control of CL and/or VL. Nine SRs/MAs were included, with different research questions and inclusion/exclusion criteria. The methods analysed for vector control can be broadly classified into (1) indoor residual spraying (IRS); (2) insecticide-treated nets (ITNs; including insecticide-impregnated bednets); (3) insecticide-treated curtains (ITCs; including insecticide-treated house screening); (4) insecticide-treated bedsheets (ITSs) and insecticide-treated fabrics (ITFs; including insecticide-treated clothing) and (5) durable wall lining (treated with insecticides) and other environmental measures to protect the house; (6) control of the reservoir host; and (7) strengthening vector control operations through health education. The existing SRs/MAs include a large variation of different primary studies, even for the same specific research sub-question. Also, the SRs/MAs are outdated, using available information until earlier than 2018 only. Assessing the quality of the SRs/MAs, there is a considerable degree of variation. It is therefore very difficult to summarise the results of the available SRs/MAs, with contradictory results for both vector indices and-if available-human transmission data. Conclusions of this meta-review are that (1) existing SRs/MAs and their results make policy recommendations for evidence-based vector control difficult; (2) further work is needed to establish efficacy and community effectiveness of key vector control methods with specific SRs and MAs (3) including vector and human transmission parameters; and (4) attempting to conclude with recommendations in different transmission scenarios.

Cytokine saga in visceral leishmaniasis

In humans, infection with Leishmania manifests into a spectrum of diseases. The manifestation of the diseases depend on the resultant evasion of the parasite to immune responses namely by macrophages, which is an exclusive host of Leishmania. The B cells valiantly mount antibody responses, however, to no avail as the Leishmania parasites occupy the intracellular niches of the macrophages and subvert the immune response. Extensive studies have been documented on the role of cell-mediated immunity (CMI) in protection and counter survival strategies of the parasites leading to downregulation of CMI. The present review attempts to discuss the cytokines in progression or resolution of visceral form of leishmaniasis or kala-azar, predominantly affecting the Indian subcontinent. The components/cytokine(s) responsible for the regulation of the critical balance of T helper cells and their subsets have been discussed in the perspective. Therefore, any strategy involving the treatment of visceral leishmania (VL) needs to consider the balance and regulation of T cell function.

Antileishmanial Potential of Propolis Essential Oil and Its Synergistic Combination With Amphotericin B

The antileishmanial activity of Tunisian propolis essential oil (EO) and its combination with amphotericin B was investigated against 2 local clinical strains of Leishmania: Leishmania major and Leishmania infantum. The cytotoxic potential of this EO was evaluated against macrophage Raw264.7. Combination of propolis EO and amphotericin B was investigated using the checkerboard method. The propolis sample was collected from the region of Beni Khalled, a Tunisian city located west of Cape Bon (Nabeul). Its location is particular since it is near to sea with a steppe climate and the predominance of citrus trees. The EO was obtained by Clevenger-type apparatus. Its chemical composition was identified using gas chromatography with flame ionization detector and gas chromatography-mass spectrometry analysis. Our results demonstrate that Tunisian propolis EO exhibit good antileishmanial activity against L. major and L. infantum promastigotes (IC50 = 5.29 ± 0.31 and 3.67 ± 0.52 µg/mL, respectively) and amastigotes (IC50 = 7.38 ± 0.45 and 4.96 ± 0.24 µg/mL, respectively). Moreover, it reduced significantly the parasite proliferation on a dose-dependent response (95%) with low cytotoxicity (selectivity index = 16.18 and 23.33, respectively). Its combination with amphotericin B showed a synergistic potential (fractional inhibitory concentration = 0.37). Interestingly, the data suggest that propolis EO was involved in macrophage activation by hyperproduction of NO. A total of 51 compounds were identified in the propolis EO. The major compound identified was α-pinene (36.7% ± 2.36%) followed by α-cedrol (6.7% ± 0.10%), totarol (6.6% ± 0.09%), and dehydroabietane (5.2% ± 0.10%). Our findings suggest that Tunisian propolis might constitute a promising source for antileishmanial molecules.