Asymptomatic Visceral Leishmaniasis Research Articles

A review of non-invasive samples and tools in kala-azar diagnosis and test of cure

The recurrence of visceral leishmaniasis (VL), also called kala-azar (KA), in endemic regions of tropical countries like India, is primarily attributed to asymptomatic VL, post-kala azar dermal leishmaniasis (PKDL), and human immunodeficiency virus (HIV) co-infection. To effectively manage VL cases and elimination targets, an early and rapid diagnosis as well as accurate field surveillance is highly essential. The traditional sampling methods like bone marrow (BM), spleen, and lymph node (LN) tissue aspirations are invasive, painful, tedious, and prone to nosocomial infections, require skilled persons and hospital facilities, and are not feasible in rural areas. Therefore, there is an urgent requirement for the adoption of a patient-friendly, non-invasive, non-hospitalized sampling procedure that ensures an effective VL diagnosis. This review aims to meticulously evaluate the most recent scientific research that focuses on the precision, feasibility, and applicability of non-invasive sampling (NIS) and techniques for the diagnosis and test of cure of VL, particularly in resource-limited settings. Apart from that, the non-invasive techniques (NIT) that have shown promising results while monitoring VL treatment response and relapse are also reviewed. The limitations associated with NIT and possible improvements in this regard are discussed as well to improve the diagnosis and management of VL.

1401. Asymptomatic Visceral Leishmaniasis in U.S. Soldiers Previously Deployed to Afghanistan

Abstract Background Visceral leishmaniasis (VL) is a chronic protozoal disease caused from the bite of an infected sand fly. VL due to Leishmania infantum is endemic in Afghanistan, although its distribution is poorly characterized. The spectrum of VL ranges from asymptomatic to active VL with symptoms of fever, weight loss, organomegaly, and pancytopenia. Most symptomatic patients die without treatment; asymptomatic patients remain at risk lifelong for symptomatic reactivation—especially if immunosuppressed. Travelers returning from VL endemic areas may harbor latent infection years after their return. We aimed to determine the prevalence of asymptomatic VL (AVL) in US military personnel previously deployed to Afghanistan. Methods Healthy adult US military personnel who deployed to Afghanistan over summer months were recruited from the Washington DC area. 90 volunteers completed a risk factor survey, blood draw, and had completed results. Diagnostic testing utilized Leishmania ELISA, interferon gamma release assay (IGRA), and quantitative PCR (qPCR). Statistical analyses included Fisher exact test, Pearson χ2 test, Welch Two Sample t-test, and Mann-Whitney U test. IRB approval was obtained. Results The prevalence of AVL (ELISA, IGRA, or qPCR positivity) in the volunteers was 9/90 (10%). Two (2.2%) PCR, 7 (7.8%) ELISA, and no (0%) IGRA samples were positive. AVL+ participants were a median of 10.6 years (range 8 - 18.6) post Afghanistan deployment, and compared to AVL- volunteers, were older (median 50 versus 40 years, p= 0.008) and more likely to self-identify as African-American (n = 5 (56%) vs 16 (20%), p = 0.029). No risk factors for AVL were identified in exploratory analysis of the volunteers’ military roles, types of outdoor exposure, or deployment location within Afghanistan. Conclusion In this preliminary cross-sectional analysis of US military personnel who returned from Afghanistan, the prevalence of AVL was 10%–comparable to other published studies on the prevalence of AVL in endemic areas and of concern when one considers the several million US military personnel previously deployed to Iraq and Afghanistan. Due to the persistence of this intracellular infection, clinicians should be alerted for reactivation potential in previously deployed Servicemembers. Disclosures Naomi E. Aronson, MD, british medical journal: Honoraria|British Medical Journal: honoraria for writing chapter for Best Evidence|Elsevier: royallties serve as textbook editor|Elsevier: Royalties as text editor|UpTo Date: royalties for writing chapters|UpToDate: royalties for writing chapters|Wellcome Foundation: Honoraria|Wellcome Foundation: program advisory board|Wellcome Trust: Honoraria|Wellcome Trust: program advisory board Naomi E. Aronson, MD, british medical journal: Honoraria|British Medical Journal: honoraria for writing chapter for Best Evidence|Elsevier: royallties serve as textbook editor|Elsevier: Royalties as text editor|UpTo Date: royalties for writing chapters|UpToDate: royalties for writing chapters|Wellcome Foundation: Honoraria|Wellcome Foundation: program advisory board|Wellcome Trust: Honoraria|Wellcome Trust: program advisory board

The Association of Human Leucocyte Antigen (HLA) Class I and II Genes with Cutaneous and Visceral Leishmaniasis in Iranian Patients: A Preliminary Case-Control Study.

Leishmaniasis is currently considered a re-emerging or emerging infection based on the geographic region. The outcome of leishmaniasis vastly depends on Leishmania-host interaction. This preliminary study aimed to show the association of human leukocyte antigen (HLA) class I and II genes with healed and non-healed cutaneous leishmaniasis (CL), and symptomatic and asymptomatic visceral leishmaniasis (VL) compared with control groups in Iran. Ninety-five people, including 31 patients versus 64 individuals in the control group, were enrolled. Among them, 20 patients had confirmed CL based on amastigote observation, 10 had improved CL and 10 non-healed CL. Eleven patients were suffering from confirmed VL based on direct agglutination test (Five asymptomatic and six symptomatic VL cases). Besides, they were residents in an endemic area of VL in the northwest of Iran. To select a control group, it was ensured that they had no history of leishmaniasis. Peripheral blood samples were collected from each patient. After DNA extraction, HLA typing was conducted using polymerase chain reaction - sequence-specific priming (PCR-SSP). Subsequently, data were statistically analyzed by SPSS. There was a statistical relationship between the presence of HLA-A26 and CL, healed CL and the existence of the B38 allele, C1 allele and symptomatic VL, as well as B1.4 allele and asymptomatic VL (P<0.05). This primary finding indicates that several HLA genes have a potential role in the susceptibility of Iranian people to CL and VL.

Potential Biomarkers for Asymptomatic Visceral Leishmaniasis among Iraq-Deployed U.S. Military Personnel.

Visceral leishmaniasis (VL) is a chronic infection caused by Leishmania (L.) donovani or L. infantum parasites. Despite having the infection, most individuals never develop the clinical disease and are able to control the parasite and remain asymptomatic. However, some progress to symptomatic VL, leading to death if untreated. The host immune response has a major role in determining the progression and severity of the clinical manifestations in VL; several immune biomarkers of symptomatic VL have been described with interferon-gamma release as a surrogate biomarker of host cellular immunity. However, new biomarkers to identify asymptomatic VL (AVL) are needed for the identification of people at risk for VL activation. In our study, levels of chemokine/cytokine in the supernatants of peripheral mononuclear blood cells (PBMC) from 35 AVL+ Iraq-deployed participants, stimulated in vitro with soluble Leishmania antigen for 72 h, were assessed by a bead-based assay that allows the measurement of multiple analytes. PBMC of AVL-negative military beneficiaries were used as controls. Monocyte Chemoattractant Protein-1, Monokine Induced by Gamma Interferon and Interleukin-8, were detected at high levels in AVL+ stimulated cultures from Iraq deployers compared to uninfected controls. Measurement of chemokine/cytokine levels can identify cellular immune responses in AVL+ asymptomatic individuals.

Asymptomatic Leishmania donovani infection and associated factors among blood donors attending at Metema district Blood Bank, Northwest Ethiopia: a cross- sectional study

BackgroundEthiopia is one of the top 10 countries in the world where 90% visceral leishmaniasis cases are reported. Metema-Humera lowlands are the most important foci in Ethiopia. Blood transfusion in visceral leishmaniasis endemic foci in Ethiopia does not consider screening of visceral leishmaniasis during blood donation. The aim of this study is therefore, was to assess asymptomatic Leishmania donovani infection and associated factors among blood donors attending at Metema district Blood Bank, Northwest Ethiopia.MethodsA Health facility based cross-sectional study was conducted at Metema Blood Bank from February to March 2020. A total of 205 blood donors were eligible and participated in this study. Structured questionnaire were used to collect data on socio-demographic characteristics and perceived risk factors associated with asymptomatic visceral leishmaniasis among blood donors. Blood donors were screened using both rK39 and direct agglutination tests based on the manufactures’ instructions. Data were analyzed using SPSS version 20.0. Chi-square test was used to assess associations of Leishmania donovani infection with predisposing factors. Associations were considered statstically significant on P-value < 0.05 at 95% confidence level.ResultsOf the total 205 participants, 32(15.6%) were positive for asymptomatic Leishmania donovani infection at least by one of the diagnostic tests used. Eight (3.9%) and 30(14.6%) of the participants` were positive by the rK39 and direct agglutination tests, respectively. Six (2.9%) donors were tested positive by both diagnostic tests. Family history of visceral leishmaniasis (X²=11.334, P = 0.003) and having neighbors with history of visceral leishmaniasis (X²=5.923, P = 0.015) were significantly associated with asymptomatic Leishmania donovani infection among blood donors.ConclusionsThe prevalence of asymptomatic Leishmania donovani infection was 15.6%. Asymptomatic visceral leishmaniasis was significantly associated with donors’ family and neighbors’ history of infection. Therefore, laboratory screening of blood donors for visceral leishmaniasis in endemic areas will be mandatory. Moreover, this study will give base line information for future study in the country.

Leukoreduction as a control measure in transfusion transmission of visceral leishmaniasis.

Asymptomatic visceral leishmaniasis (VL) infection is a risk for transfusion safety. Leukoreduction has been an alternative for the prevention of some blood-borne diseases, including VL. This study aimed to evaluate the role of leukoreduction of cellular blood components as a control measure for transfusional VL transmission. A total of 161 polytransfused patients with non-leukoreduced blood components (HNL), 95 polytransfused with leukoreduced blood components (LH), and 202 non-transfused (NT) from endemic regions for VL and with a similar epidemiological profile. The detection of antibodies against VL was performed by ELISA and the presence of the parasite was investigated by real-time PCR. Statistical significance was defined as p < .05. When comparing three groups, ELISA results were statistically significant (p=.0065). The residual analysis of ELISA showed statistically significant for the HNL group compared to the general group (p=.002; OR: 5.6; CI: 1.7-25.8), demonstrating that individuals who received non-leukoreduced transfusions are five times more likely to acquire Leishmania infantum infection than the general. Higher prevalence in the group with HNL and low prevalence in those who received LH, similar to NT patients, highlight the risk of transfusional VL transmission and reinforce the role of leukoreduction in its prevention.

The role of mucosal-associated invariant T cells in visceral leishmaniasis.

Mucosal-associated invariant T (MAIT) cells are restricted by MR1 and are known to protect against bacterial and viral infections. Our understanding of the role of MAIT cells in parasitic infections, such as visceral leishmaniasis (VL) caused by protozoan parasites of Leishmania donovani, is limited. This study showed that in response to L. infantum, human peripheral blood MAIT cells from children with leishmaniasis produced TNF and IFN-γ in an MR1-dependent manner. The overall frequency of MAIT cells was inversely correlated with alanine aminotransferase levels, a specific marker of liver damage strongly associated with severe hepatic involvement in VL. In addition, there was a positive correlation between total protein levels and the frequency of IL-17A+ CD8+ MAIT cells, whereby reduced total protein levels are a marker of liver and kidney damage. Furthermore, the frequencies of IFN-γ+ and IL-10+ MAIT cells were inversely correlated with hemoglobin levels, a marker of severe anemia. In asymptomatic individuals and VL patients after treatment, MAIT cells also produced IL-17A, a cytokine signature associated with resistance to visceral leishmaniasis, suggesting that MAIT cells play important role in protecting against VL. In summary, these results broaden our understanding of MAIT-cell immunity to include protection against parasitic infections, with implications for MAIT-cell-based therapeutics and vaccines. At last, this study paves the way for the investigation of putative MAIT cell antigens that could exist in the context of Leishmania infection.

Distance-based paper device using combined SYBR safe and gold nanoparticle probe LAMP assay to detect Leishmania among patients with HIV

Asymptomatic visceral leishmaniasis cases increase continuously, particularly among patients with HIV who are at risk to develop further symptoms of leishmaniasis. A simple, sensitive and reliable diagnosis is crucially needed due to risk populations mostly residing in rural communities with limited resources of laboratory equipment. In this study, a highly sensitive and selective determination of Leishmania among asymptomatic patients with Leishmania/HIV co-infection was achieved to simultaneously interpret and semi-quantify using colorimetric precipitates (gold-nanoparticle probe; AuNP-probe) and fluorescence (SYBR safe dye and distance-based paper device; dPAD) in one-step loop-mediated isothermal amplification (LAMP) assay. The sensitivities and specificities of 3 detection methods were equivalent and had reliable performances achieving as high as 95.5%. Detection limits were 102 parasites/mL (0.0147 ng/µL) which were 10 times more sensitive than other related studies. To empower leishmaniasis surveillance as well as prevention and control, this dPAD combined with SYBR safe and gold nanoparticle probe LAMP assay is reliably fast, simple, inexpensive and practical for field diagnostics to point-of-care settings in resource-limited areas which can be set up in all levels of healthcare facilities, especially in low to middle income countries.

An assessment of serological techniques for the identification of asymptomatic visceral leishmaniasis in blood donors in Northeastern Brazil

Background: Visceral leishmaniasis (VL) is a neglected disease caused by species of the Leishmania donovani complex and transmitted mainly by the bite of infected sandflies. A less frequent form of transmission is the transfusion route, important in countries lacking screening procedures for VL in blood banks. Methods: To identify asymptomatic infection by Leishmania sp, our goal here was to evaluate and compare the performance of three different serological techniques: Flow Cytometry (FC); Direct Agglutination Test (DAT); and Immunoenzymatic Test (ELISA). Thirty-one asymptomatic carriers of L. infantum were selected, from a single blood bank located in Recife, northeastern Brazil. Results : Foi avaliada a frequência de amostras positivas assintomáticas nos testes, no ELISA baseado no antígeno solúvel de Leishmania (25,8%), FC (22,8%), DAT (9,7%) e ELISA baseado em uma única proteína recombinante (12,9%). A sensibilidade dos testes também foi avaliada, o FC (22,58%) e o ELISA com o antígeno solúvel (22,58%) apresentaram os maiores valores de sensibilidade que o DAT (6,45%) e o ELISA recombinante (12,9%). Apenas a CF apresentou baixa especificidade (22,22%), em contraste com as demais técnicas (100% de especificidade). Conclusion: Given the results presented, we highlight the low effectiveness of serological techniques for the identification of asymptomatic individuals, thus emphasizing the need to develop more accurate methods for this purpose.

The human immune response to saliva of Phlebotomus alexandri, the vector of visceral leishmaniasis in Iraq, and its relationship to sand fly exposure and infection.

BackgroundSand fly saliva exposure plays an important role in immunity against leishmaniasis where it has mostly been associated with protection. Phlebotomus (Ph.) alexandri transmits Leishmania (L.) infantum, the causative agent of visceral leishmaniasis (VL), in Iraq. Our group recently demonstrated that 20% of Operation Iraqi Freedom (OIF) deployers had asymptomatic VL (AVL) indicative of prior infection by the parasite L. infantum. Little is known about Ph. alexandri saliva, and the human immune response to it has never been investigated. Here, we characterize the humoral and cellular immune response to vector saliva in OIF deployers naturally exposed to bites of Ph. alexandri and characterize their immunological profiles in association to AVL.Methodology/Principal findingsThe humoral response to Ph. alexandri salivary gland homogenate (SGH) showed that 64% of 200 OIF deployers developed an antibody response. To assess the cellular immune response to saliva, we selected a subcohort of subjects based on their post-travel (median 4 months; range 1–22 months) antibody response (SGH Antibody [Ab] positive or negative) as well as their AVL status; ten never-traveled controls were also included. Banked peripheral blood mononuclear cells (PBMC), collected ~10 years after end of deployment, were stimulated with SGH for 96 hours. The levels of IFN- γ, IL-6, IL-10, IL-13 and IL-17 were determined by ELISA. Our findings indicate that OIF deployers mounted a cellular response to SGH where the anti-SGH+ asymptomatic subjects developed the highest cytokine levels. Further, stimulation with SGH produced a mixture of pro-inflammatory and anti-inflammatory cytokines. Contrary to our hypothesis, we observed no correlation between the cellular immune response to Ph. alexandri SGH and prevention from asymptomatic infection with L. infantum.Conclusions/SignificanceAs we found, although all infected deployers demonstrated persistent disease control years after deployment, this did not correlate with anti-saliva systemic cellular response. More exposure to this vector may facilitate transmission of the L. infantum parasite. Since exposure to saliva of Ph. alexandri may alter the human immune response to bites of this vector, this parameter should be taken into consideration when considering the VL risk.

Prevalence of asymptomatic visceral leishmaniasis in human and dog, Benishangul Gumuz regional state, Western Ethiopia

BackgroundThe Benishangul-Gumuz region is an important development corridor in Ethiopia. Large-scale projects such as the Great Renaissance Dam, mining and agriculture have entailed huge environmental modifications and settlement pattern changes. There is no detailed epidemiological information on visceral leishmaniasis (VL) in the region.Materials and methodsA cross-sectional study was carried out to assess the epidemiology and risk factors associated with Leishmania infection. A leishmanin skin test (LST) was done for 1342 participants, and for 253 of them rK39 and DAT were carried out. Thirty-six dogs owned by households with LST-positive member(s) were rK39 and DAT tested. A pretested questionnaire was used to capture individual and household characteristics.ResultsOf the 89.2% (1197/1342) who availed themselves of the LST reading, 6.0% were positive. The rk39 and DAT positivity among the 253 tested were 3.2% and 5.9%, respectively. In dogs, positivity rates by rK39 and DAT were 13.9% and 5.6%, respectively. Of the household and individual risk factors, presence of a dog in the household (P = 0.005), male sex (0.003), residence woreda (0.000) and occupation (0.023) showed a strong positive association with LST positivity. Individuals who lived in households that had dogs were 2.6 times more likely to be LST positive (AOR = 2.6; 95% CI = 1.54, 4.40). Being female decreased the probability of being LST positive by 0.38 times (AOR = 0.38; 95% CI = 0.20, 0.72). People living in Guba and Kurmuk had 4.7 (AOR = 4.74, 95% CI 1.83, 12.31) and 5.9 (AOR = 5.85, 95% CI 2.27, 15.09) times more risk of being infected.ConclusionsWe demonstrated the presence of active VL transmission in the areas. Thus, we underline the need to establish the responsible vector(s) and reservoir(s) for comprehensive early containment plans to prevent potentially harmful public health and economic consequences.Graphical

A critical review of the applicability of serological screening for Leishmaniasis in blood banks in Brazil.

Leishmaniasis is a group of diseases caused by several species of protozoa. It is a major public health concern in its visceral form, accounting annually for 59,000 deaths, and an estimated 12 million infected patients per year. The importance of VL resides not only in its high incidence and wide distribution but also in the possibility of the disease progressing to the severe and lethal forms, especially in children and immunosuppressed individuals, when associated with malnutrition and concomitant infections. This study is a bibliographical review, aiming to understand the sensitivity and specificity parameters of the tests used to detect Leishmaniasis, as well as to understand if there is any relevance in proposing a serological screening for Leishmaniasis in blood banks. In general, we observed that there are currently several types of tests for detecting Leishmaniasis: parasitological, serological and molecular. In such tests, many serological methods and kits are available for the detection of asymptomatic visceral leishmaniasis, but there is variability in sensitivity and specificity among the methods. The gold standard for the diagnosis of visceral leishmaniasis is the parasitological method, through the aspiration of bone marrow, with higher sensitivity by splenic puncture. Due to the relevance of the disease and the available data from research centers, there is evidence to propose a transfusion serological screening for visceral Leishmaniasis, pointing to the need for further studies.

Leishmania ITS1 Is Genetically Divergent in Asymptomatic and Symptomatic Visceral Leishmaniasis: Results of a Study in Southern Iran.

It has been documented that the genotypic traits in symptomatic and asymptomatic cases of visceral leishmaniasis (VL) may be different. The current study aimed to find out and compare the genotype and intraspecies diversity of Leishmania Internal Transcribed Spacer 1 (ITS1) from asymptomatic and symptomatic VL cases in southern Iran. Methods. Buffy coat samples from seven VL patients, with clinical signs and symptoms, and seven asymptomatic VL cases, were evaluated in this study. Samples of asymptomatic individuals were obtained from children living in a VL endemic area in southern Iran, while the samples of symptomatic subjects were obtained from patients admitted to hospitals with a diagnosis of VL. DNA was extracted from the buffy coats of the samples and PCR-amplified, targeting the ITS1of Leishmania. The PCR products were sequenced, and the consensus sequences were assembled and multiple-aligned with a set of Leishmania strains retrieved from the GenBank, using Clustal W. The phylogenetic tree was rooted, using MEGAX software, and the diversities based on haplotype and nucleotides, as well as the number of polymorphic sites, were measured using DnaSP v5.0 software. The results of ITS1 sequencing in 5 out of 7 asymptomatic VL cases showed 99.25% to 100% similarity with the Leishmania infantum ITS1 sequence (accessed number: MN648746), and one isolate was considered as just Leishmania sp. In one sample, 99.75% similarity was seen with the ITS1 sequence of Crithidia fasciculata. Of the symptomatic VL patients, the PCR product revealed a 340 bp band corresponding to L. infantum in all of the samples. By analyzing the ITS1 sequences, all seven sequences formed a clade somewhat different from other Leishmania species and considered as Leishmania sp. Haplotype and nucleotide diversity were much more prevalent in symptomatic cases where six haplotypes were seen in the ITS1 of Leishmania from symptomatic patients and only two haplotypes were observed in the samples from asymptomatic cases. The findings of the current study showed that the Leishmania ITS1 from symptomatic VL and asymptomatic cases has significant genetic differences. Besides, infection with Crithidia fasciculata was reported, for the first time, in an asymptomatic case, which deserves further study.

Conversion of asymptomatic infection to symptomatic visceral leishmaniasis: Astudy of possible immunological markers.

IntroductionPresence of asymptomatic individuals in endemic areas is common. The possible biomarkers in asymptomatic individuals once they get exposed to infection as well as following conversion to symptomatic disease are yet to be identified.We identified asymptomatic Visceral leishmaniasis (VL) infection amongst rK39+sorted direct agglutination test positive (DAT+) endemic healthy population and confirmed it by quantitative PCR(qPCR).The immunological determinants such as Adenosine deaminase (ADA), Interferon gamma (IFN-γ), Tumour Necrosis Factor alpha (TNF-α) and Interleukin 10 (IL-10)were examined to predict probable biomarkers for conversion to symptomatic VL.MethodsSample size was 5794 healthy individuals from VL endemic region. Antibody tests(DAT &rK39) were performed and later a qPCR assay was employed using kDNA specific primers and probes. Immunological biomarkers examined were ADA level by ADA–MTP kit and quantitative cytokines(IFN-γ, IL-10 and TNF-α) by ELISA.Results120 asymptomatic individuals of 308 rK39 sero-positives were DAT positive comprising of 56 with previous history and 64 with no history of VL. RT-PCR confirmed asymptomatic VL in 42 sero-positives. These were followed up through repeated qPCR and evaluation of immunological determinants. We observed10 symptomatic cases converted from a total of 42 asymptomatic individuals identified at base-line. The level of ADA, IL-10 and IFN-γ remained consistently high in asymptomatic cases and amongst these, ADA and IL-10 but not IFN-γ remained higher at the development of clinical symptoms into active VL. On the contrary, there was no significant change in the mean concentration of TNF-α at both stages of the disease.DiscussionWe surmise from our data that considerable proportion of asymptomatic cases can be a reservoir and may play a crucial role in transmission of visceral leishmaniasis in endemic areas.The data also suggests that ADA and IL-10 can serve as a potential biomarker during the conversion of asymptomatic into symptomatic VL.

Prospection of immunological biomarkers for characterization and monitoring of asymptomatic Leishmania (Leishmania) infantum infection.

In areas endemic for Leishmania infantum, an asymptomatic infection may be an indicator of the extent of transmission. The main goal of this study was to evaluate the applicability of measuring circulating immunological biomarkers as an alternative strategy to characterize and monitor L. infantum asymptomatic infections in combination with serological methods. To this end, 179 children from a region endemic for visceral leishmaniasis (VL), aged 1-10 years old, selected from a cross-sectional study, were identified as asymptomatic (n = 81) or uninfected (n = 98) by qPCR and/or serological tests (ELISA using L. infantum soluble antigen and rK39), and, together with serum samples of children diagnosed with VL (n = 43), were subjected to avidity tests and cytokine levels measurement. Avidity rates (AR) ranging from 41 to 70% were found in 29 children (66%) from the asymptomatic group. On the other hand, high AR (above 70%) were observed in 27 children (64%) from the VL group. Logistic Regression and Classification and Regression Tree (CART) analyses demonstrated that lower AR and IFN-γ production associated with higher IL-17A levels were hallmarks in asymptomatic L. infantum infections. Therefore, this study proposes an association of immunological biomarkers that can be used as a complementary strategy for the characterization and monitoring of asymptomatic VL infections in children living in endemic areas.

An epidemiological study of visceral leishmaniasis in North East Ethiopia using serological and leishmanin skin tests.

BackgroundIn Ethiopia, visceral leishmaniasis (VL) is caused by Leishmania donovani. The estimated country-wide incidence of VL in Ethiopia is 3700–7400 cases/year. The balance between anthroponotic and zoonotic transmission is still unknown even though most authors believe that visceral leishmaniasis in East Africa is anthroponotic. Asymptomatic leishmania infections occur more frequently than clinically apparent visceral leishmaniasis cases. The aim of this study was to determine the prevalence of asymptomatic VL infection and assess the degree of exposure among residents in Raya Azebo Woreda villages where cases of VL were recently reported.MethodsA community based cross-sectional survey was conducted in 2013 between 1st of May and 25th of July. A total of 1099 individuals living in 314 households were included in the study. Socio-demographic and clinical data were collected from each of the participants and venous blood was also collected for the detection of antibodies to visceral leishmaniasis using Direct Agglutination Test. Leishmanin skin test was performed to detect the exposure to the parasite. Data was entered into excel and exported to SPSS version 17 for statistical analysis. Chi-square and the corresponding p-values were used to determine the statistical significance of the proportions/ratios obtained from the cross tabulated data. A p-value < 0.05 was considered statistically significant.ResultA total of 1099 study subjects comprising 401 males and 698 females were included in the study. The overall positive leishmanian skin test and sero-prevalence rates respectively were 9.08% and 0.87%. The difference in LST positivity by age group and sero-prevalence by sex were statistically significant (P <0.01 and P<0.05 respectively). Out of the 9 sero-positive individuals, 7 had no history of travel to visceral leishmaniasis endemic areas out of Raya Azebo.ConclusionIn general our results suggest occurrence of VL in the study area is, very low. Our survey also indicates that due to the low incidence of the disease, and lack of awareness, some patients remain under diagnosed.

Age trends in asymptomatic and symptomatic Leishmania donovani infection in the Indian subcontinent: A review and analysis of data from diagnostic and epidemiological studies.

BackgroundAge patterns in asymptomatic and symptomatic infection with Leishmania donovani, the causative agent of visceral leishmaniasis (VL) in the Indian subcontinent (ISC), are currently poorly understood. Age-stratified serology and infection incidence have been used to assess transmission levels of other diseases, which suggests that they may also be of use for monitoring and targeting control programmes to achieve elimination of VL and should be included in VL transmission dynamic models. We therefore analysed available age-stratified data on both disease incidence and prevalence of immune markers with the aim of collating the currently available data, estimating rates of infection, and informing modelling and future data collection.Methodology/Principal findingsA systematic literature search yielded 13 infection prevalence and 7 VL incidence studies meeting the inclusion criteria. Statistical tests were performed to identify trends by age, and according to diagnostic cut-off. Simple reversible catalytic models with age-independent and age-dependent infection rates were fitted to the prevalence data to estimate infection and reversion rates, and to test different hypotheses about the origin of variation in these rates. Most of the studies showed an increase in infection prevalence with age: from ≲10% seroprevalence (<20% Leishmanin skin test (LST) positivity) for 0-10-year-olds to >10% seroprevalence (>20% LST-positivity) for 30-40-year-olds, but overall prevalence varied considerably between studies. VL incidence was lower amongst 0-5-year-olds than older age groups in most studies; most showing a peak in incidence between ages 5 and 20. The age-independent catalytic model provided the best overall fit to the infection prevalence data, but the estimated rates for the less parsimonious age-dependent model were much closer to estimates from longitudinal studies, suggesting that infection rates may increase with age.Conclusions/SignificanceAge patterns in asymptomatic infection prevalence and VL incidence in the ISC vary considerably with geographical location and time period. The increase in infection prevalence with age and peaked age-VL-incidence distribution may be due to lower exposure to infectious sandfly bites in young children, but also suggest that acquired immunity to the parasite increases with age. However, poor standardisation of serological tests makes it difficult to compare data from different studies and draw firm conclusions about drivers of variation in observed age patterns.

Asymptomatic Visceral Leishmania infantum Infection in US Soldiers Deployed to Iraq.

Visceral leishmaniasis (VL), due to Leishmania infantum, is a persistent intracellular parasitic infection transmitted by the bite of infected sand flies. Symptomatic VL has been reported in U.S. soldiers with Iraq deployment. Untreated symptomatic VL can be fatal; asymptomatic VL (AVL) may establish a lifelong risk of reactivation. We report prevalence and AVL risk factors in Operation Iraqi Freedom (OIF) deployers during 2002-11. Healthy soldiers exposed to VL endemic areas in Iraq and 50 controls who never traveled to endemic regions were recruited through military healthcare facilities (2015-17). Responses to a risk factor survey and blood samples were obtained. Leishmania research diagnostics utilized included enzyme-linked immunosorbent assay (ELISA), rk39 test strips, quantitative polymerase chain reaction (PCR), and interferon gamma release (IGRA) assays. Statistical analyses included Fisher exact test, Pearson χ2 test, Mann-Whitney U test, and logistic regression. 200 deployed subjects were enrolled, mostly males (84.0%), of white ethnicity (79.0%), and median age 41 (range 24-61) years. 64% were seropositive for Phlebotomus alexandri saliva antibodies. Prevalence of AVL (any positive test result) was 39/200 (19.5%, 95% confidence interval 14.4%-25.8%). Two (1.0%) PCR, 10 (5%) ELISA, and 28 (14%) IGRA samples were positive. Travel to Ninewa governorate increased risk for AVL (P = .01). AVL was identified in 19.5% of OIF deployers; travel to northwest Iraq correlated with infection. Further studies are needed to inform risk for reactivation VL in US veterans and to target additional blood safety and surveillance measures.

Detection of Leishmania DNA in saliva among patients with HIV/AIDS in Trang Province, southern Thailand

Leishmaniasis is a neglected tropical disease causing opportunistic infection among patients with HIV/AIDS. The fatal form of this disease is visceral leishmaniasis (VL). DNA of Leishmania can be detected in saliva, for which the collection is noninvasive and requires little expertise. This study aimed to evaluate the sensitivity and specificity of a nested-PCR to amplify the Internal Transcribed Spacer 1 (ITS1) to detect Leishmania DNA in paired saliva and buffy coat samples of 305 Thai patients with HIV/AIDS in Trang Hospital, Trang Province, southern Thailand. For asymptomatic Leishmania infection among Thai patients with HIV/AIDS, the sensitivity and specificity of the nested-PCR-ITS1 in buffy coat were 73.9 and 100%, respectively. However, the sensitivity in saliva was 26.1% and specificity was 100%. Using the nested-PCR-ITS1, saliva and buffy coat samples showed positive agreement in only 52.0% of patients. Saliva tested results with the nested-PCR-ITS1 showed positive agreement with the Direct Agglutination Test (DAT) in 46.5% of patients. Only 12.1% of the samples showed positive agreement for Leishmania infection among all the three tests: saliva, buffy coat and DAT results. Using nucleotide sequencing, at least three species of Leishmania infection were identified in saliva, i.e., L. siamensis (n = 28), L. martiniquensis (n = 9), and L. donovani complex (n = 1). As a result, buffy coat still appears to be a better specimen to diagnose asymptomatic VL infection among individuals with HIV. However, the use of both buffy coat and saliva together as clinical specimens would increase the sensitivity of Leishmania detection.

High frequency of subclinical Leishmania infection among HIV-infected patients living in the endemic areas of visceral leishmaniasis in Fars province, southern Iran.

Visceral leishmaniasis (VL) is a major health concern in patients with HIV infection in endemic areas of VL. In these areas, a substantial number of infected individuals are asymptomatic and the risk of acute VL infection in HIV/VL co-infected cases is high. The current study aimed to determine the prevalence of asymptomatic VL infection among HIV-infected patients in Fars province, southern Iran. Subjects of the study were 251 HIV-confirmed patients who all were clinically asymptomatic for leishmaniasis. Blood samples were obtained from each participant. Anti-Leishmania antibodies were detected in the sera using ELISA. DNA was extracted from the buffy coat of each subject and PCR amplified, targeting an ITS-2 gene of Leishmania. PCR products were purified from the gel and were sequenced. Overall, 19 out of 251 (7.6%) HIV-infected patients were found to be infected with Leishmania, using serological or molecular methods. Anti-Leishmania antibodies were detected in 13 (5.2%) patients and leishmanial DNA in 8 (3.2%) of the patients. The sequence analysis of DNA-positive cases revealed the species of the parasite as L. infantum. The high prevalence of VL among the patients with HIV is a serious challenge which demands further attention to improve the prophylaxis and treatment measurements of VL/HIV co-infection and thereby promoting the life expectancy and quality of life of these patients.