Leishmania donovani in blood smears of asymptomatic persons

Immunotherapeutic efficacy of Th1 stimulatory epitopes derived from Leishmania donovani enolase and triose phosphatase isomerase in experimental visceral leishmaniasis

Visceral leishmaniasis is a lethal systemic disease which cannot be controlled by drugs alone given asymptomatic reservoirs and must include alternatives to modulate immune responses of the endemic contacts. Our previous studies have yielded potential immunomodulatory proteins by proteomic approach and their peptides showed significant immunomodulation and prophylactic efficacies. The current study has been intended to evaluate immunotherapeutic potential of the lead peptides (P10, P14 and P15) and their combinations with BCG as adjuvant. Results indicated P10 + 14 as well as P10 + P15 to be the most potential therapeutic peptides cocktails as both these combinations reduced parasite burden by > 65 % eliciting remarkable cellular response. High level of IFN-γ, TNF-α and IL-12 with decreased TGF-β expression suggested skewing of immune response towards Th1 type. These results were further supported by strong DTH and lymphoproliferative responses indicating therapeutic potential of the peptide combinations and possibilities in Kala-azar elimination program.

From Infection to Death: An Overview of the Pathogenesis of Visceral Leishmaniasis

Kala-azar, also known as visceral leishmaniasis (VL), is a disease caused by Leishmania infantum and L. donovani. Patients experience symptoms such as fever, weight loss, paleness, and enlarged liver and spleen. The disease also affects immunosuppressed individuals and has an overall mortality rate of up to 10%. This overview explores the literature on the pathogenesis of preclinical and clinical stages, including studies in vitro and in animal models, as well as complications and death. Asymptomatic infection can result in long-lasting immunity. VL develops in a minority of infected individuals when parasites overcome host defenses and multiply in tissues such as the spleen, liver, and bone marrow. Hepatosplenomegaly occurs due to hyperplasia, resulting from parasite proliferation. A systemic inflammation mediated by cytokines develops, triggering acute phase reactants from the liver. These cytokines can reach the brain, causing fever, cachexia and vomiting. Similar to sepsis, disseminated intravascular coagulation (DIC) occurs due to tissue factor overexpression. Anemia, hypergammaglobulinemia, and edema result from the acute phase response. A regulatory response and lymphocyte depletion increase the risk of bacterial superinfections, which, combined with DIC, are thought to cause death. Our understanding of VL's pathogenesis is limited, and further research is needed to elucidate the preclinical events and clinical manifestations in humans.

Assessing L. donovani Skin Parasite Load: A Proof of Concept Study of a Microbiopsy Device in an Indian Setting

Background

In the endgame of the elimination initiative of visceral leishmaniasis (VL) on the Indian subcontinent, one of the main questions remaining is whether asymptomatically infected individuals also contribute to transmission. We piloted a minimally invasive microbiopsy device that could help answer this question. While the potential of this device has been previously illustrated in Ethiopia, no such information is available for the setting of the Indian subcontinent. In this proof of concept study we aimed to assess 1) to what extent skin parasite load obtained with the new microbiopsy device correlates with disease status, 2) to what extent skin parasite load correlates with blood parasite load in the same subject, and 3) to what extent the skin parasite load obtained from different sampling sites on the body correlates with one another.

Methods

We performed a pilot study in Bihar, India, including 29 VL patients, 28 PKDL patients, 94 asymptomatically infected individuals, 22 endemic controls (EC), and 28 non-endemic controls (NEC). Presence of infection with L. donovani in the blood was assessed using Direct Agglutination Test, rK39 ELISA, Whole Blood Analysis measuring IFN-γ and qPCR. A skin sample was collected with the microbiopsy device on two different locations on the body. PKDL patients provided a third skin sample from the edge of a PKDL lesion. Parasite load in the skin was measured by qPCR.

Findings

We found a clear correlation between the skin parasite load obtained with the microbiopsy device and disease status, with both higher skin parasite loads and higher proportions of positive skin samples in VL and PKDL patients compared to asymptomatics, EC, and NEC. No clear correlation between skin parasite load and blood parasite load was found, but a moderate correlation was present between the skin parasite load in arm and neck samples. In addition, we found four positive skin samples among asymptomatic individuals, and 85% of PKDL lesions tested positive using this microbiopsy device.

Conclusions

In line with previous pilot studies, our results from an Indian setting suggest that the microbiopsy device provides a promising tool to measure skin parasite load, and – if validated by xenodiagnosis studies – could facilitate much needed larger scale studies on infectiousness of human subgroups. In addition, we advocate further evaluation of this device as a diagnostic tool for PKDL.

Parasitemia and its daily variation in canine leishmaniasis

The aim of this study was to evaluate, through qPCR, the prevalence of parasitemia in sick kennel dogs naturally infected by canine leishmaniasis. An evaluation of daily changes of the parasitic load in peripheral blood was also performed. A comprehensive clinical examination and the collection of several samples (blood, lymph node, skin, and conjunctiva) were performed in 140 dogs living in an endemic area. Among these, only the dogs with clinically evident leishmaniasis were enrolled (39/140; 27.9%). Twelve (30.8%) out of 39 showed parasitemia, with a low load (median: 4 Leishmania/ml) despite a high lymph node parasite load (median: 4000 Leishmania/ml) and high IFAT titers (≥ 1:640). Seven sick dogs were sampled every 4 h for 6 times during a 24-h period, in order to obtain light- and dark-span samples. Only one (14.3%) out of the seven serial sampled dogs showed Leishmania DNA in the peripheral blood in two samples (2/42; 4.8%). Surprisingly, Leishmania DNA was also detected in the peripheral blood of asymptomatic dogs, negative to both serology and PCR performed on samples other than blood (6/101; 5.9%). The present study confirms that in canine leishmaniasis parasitemia is uncommon and even transitory. Even if recommended, microscopic examination is confirmed as a low sensitivity method with a lower diagnostic utility in canine leishmaniasis than qPCR. Moreover, circulating Leishmania DNA can be found even in healthy dogs. This finding is important in clinical practice because in endemic areas it suggests a transfusion risk and a possible transmission to the vector.

Identifying asymptomatic Leishmania infections in non-endemic villages in Gedaref state, Sudan

Objectives

Infection with the causative agent of visceral leishmaniasis (VL) may be either symptomatic or asymptomatic. In this study we aimed at investigating the prevalence of asymptomatic infections of leishmania in non-endemic villages in Gedaref state, Sudan. A descriptive cross-sectional study conducted during September and October 2014. Blood samples were collected for serological and molecular analysis. Sticky-traps, knockdown spray and CDC-miniature light traps were used for the collection of sandflies.

Results

Ninety-Five participants were included; 52 from Abukishma, 15 Algadamblia Tirfa, 25 Abualnaja and 3 were from Algadamblia Aljabal. Females constituted 56 (58.9%) of the study participants while males were 39 (41.1%). The most frequent age group was > 40-years (54.7%). Balanites/Acacia trees were the most planted tree inside the houses; 78 (82.1%). Also, 85 (89.5%) of the participants breed animals inside the house. DAT test revealed 5 positive participants (5.2%). 4/5 DAT positive were past VL infection. PCR detected 35 (36.8%) positive participants. A total of 31/35 was considered asymptomatic infections based on PCR. Households planted Balanites/Acacia trees or breed domestic animals were found in high percentages with L. donovani PCR positive participants (60.1%, 91.4%). No statistically significant was found for VL associated risk factors and VL asymptomatic participants.

Human Competence to Transmit Leishmania infantum to Lutzomyia longipalpis and the Influence of Human Immunodeficiency Virus Infection

Visceral leishmaniasis (VL) caused by Leishmania infantum is a lethal disease transmitted by sand flies. Although, considered a zoonosis with dogs held as the main reservoirs, humans are also sources of infection. Therefore, control policies currently focused on dog culling may need to consider that VL and human immunodeficiency virus (HIV)/VL patients may also be infectious, contributing to transmission. Reservoir competence of patients with VL without and with HIV infection and of persons asymptomatically infected with Leishmania was assessed by xenodiagnosis with the vector Lutzomyia longipalpis. Parasites in sand fly's guts were identified by using optical microscopy and by conventional polymerase chain reaction (PCR). Leishmania infantum blood parasite burden was determined by quantitative PCR. Among the 61 participants, 27 (44%) infected sand flies as seen by microscopy or PCR. When infectiousness was assessed by microscopy, xenodiagnosis was positive in five (25%) patients not infected with HIV, whereas nine (45%) of those harboring HIV were positive. Among the 19 asymptomatic patients four (21%) infected sand flies only demonstrated by PCR. One (50%) asymptomatic patient with HIV had a positive xenodiagnosis by microscopy. 9/372 (2.4%) and 37/398 (9.2%) sand flies were infected when feeding in patients without and with HIV, respectively. Infectiousness was poorly correlated with quantitative PCR. The study shows that asymptomatic humans are capable of transmitting L. infantum, that ill persons with HIV infection are more infectious to sand flies, and that humans are more important reservoirs than previously thought. This fact may be considered when designing control policies for zoonotic VL.

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

BACKGROUND

Age 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 FINDINGS

A 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/SIGNIFICANCE

Age 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.

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

BACKGROUND

Visceral leishmaniasis (VL) is characterised by a high degree of spatial clustering at all scales, and this feature remains even with successful control measures. VL is targeted for elimination as a public health problem in the Indian subcontinent by 2020, and incidence has been falling rapidly since 2011. Current control is based on early diagnosis and treatment of clinical cases, and blanket indoor residual spraying of insecticide (IRS) in endemic villages to kill the sandfly vectors. Spatially targeting active case detection and/or IRS to higher risk areas would greatly reduce costs of control, but its effectiveness as a control strategy is unknown. The effectiveness depends on two key unknowns: how quickly transmission risk decreases with distance from a VL case and how much asymptomatically infected individuals contribute to transmission.

METHODOLOGY/PRINCIPAL FINDINGS

To estimate these key parameters, a spatiotemporal transmission model for VL was developed and fitted to geo-located epidemiological data on 2494 individuals from a highly endemic village in Mymensingh, Bangladesh. A Bayesian inference framework that could account for the unknown infection times of the VL cases, and missing symptom onset and recovery times, was developed to perform the parameter estimation. The parameter estimates obtained suggest that, in a highly endemic setting, VL risk decreases relatively quickly with distance from a case-halving within 90m-and that VL cases contribute significantly more to transmission than asymptomatic individuals.

CONCLUSIONS/SIGNIFICANCE

These results suggest that spatially-targeted interventions may be effective for limiting transmission. However, the extent to which spatial transmission patterns and the asymptomatic contribution vary with VL endemicity and over time is uncertain. In any event, interventions would need to be performed promptly and in a large radius (≥300m) around a new case to reduce transmission risk.

Detection of Leishmania donovani in peripheral blood of asymptomatic individuals in contact with patients with visceral leishmaniasis

BACKGROUND

The majority of individuals infected with Leishmania donovani complex remain asymptomatic. They may act as transmission reservoirs for visceral leishmaniasis (VL). We investigated sero-prevalence of L. donovani complex amongst those closely associated with patients with VL and whether these sero-reactive individuals had Leishmania parasites in their peripheral blood. Other risk factors were also investigated.

METHODS

A total of 257 individuals in contact with patients with VL were tested for anti-Leishmania antibodies by rK39 immunochromatographic test (rK39 ICT), ELISA using promastigote antigen (p-ELISA) and indirect fluorescent antibody test (IFAT). Buffy coats of rK39 ICT positive individuals were cultured; sero-reactive buffy coats were tested for Leishmania DNA by ITS1 PCR. DNA obtained from culture was sequenced to confirm Leishmania species. Risk factors were evaluated for each sero-positive sample.

RESULTS

The results showed 29.2% (75/257) prevalence by serological tests: 14.4% (37/257) were positive by rK39 ICT, 25.3% (65/257) by p-ELISA, 18.3% (47/257) by IFAT and 10.9% (28/257) by all three serological methods. Ten percent (3/30) of cultures were positive for Leishmania promastigotes. Only 3% (2/74) sero-reactive buffy coats were positive for DNA; sequence analysis revealed L. donovani species. Significant risk factors were age, working as farmers, domestic animals in household and proximity to animal shelters.

CONCLUSIONS

Asymptomatic family members of patients with VL can carry live L. donovani in peripheral blood and may act as potential reservoirs.

GENBANK ACCESSION NUMBER

BankIt1863680 Leishmania KT921417 (DNA sequences of the ribosomal ITS1 region of L. donovani).

Serological and Molecular Analysis of Leishmania Infection in Healthy Individuals from Two Districts of West Bengal, India, Endemic for Visceral Leishmaniasis

AbstractSeveral epidemiological studies have indicated the presence of asymptomatic infections with Leishmania donovani in the Indian subcontinent, where parasite transmission is considered anthroponotic. In India, such asymptomatic Leishmania cases have been identified in the state of Bihar. We explored here, the presence of asymptomatic Leishmania infection among healthy individuals living in two districts in the state of West Bengal, India, using serological and molecular tests. Blood samples of 246 healthy individuals were collected from nine villages of Malda and Murshidabad districts in West Bengal, considered endemic for visceral leishmaniasis (VL). Real-time quantitative polymerase chain reaction (qPCR) was performed for the quantification of parasite load in the blood. In addition, two serological tests were carried out to demonstrate anti-Leishmania antibodies: rK39 strip test and anti-total soluble Leishmania antigen IgG using enzyme-linked immunosorbent assay method. Nearly one-fifth (53/246) of the screened population was positive in qPCR as against 10.97% (27/246) positive in rK39 strip test. A range of parasite load was observed in the blood of identified asymptomatic Leishmania cases with a median value of 7.7 parasites/mL (range = 1-65). There was poor agreement between qPCR and serological tests (κ = 0.089, P = 0.13), and 29.62% and 20.54% of the population were qPCR positive in seropositive and seronegative groups, respectively. Combined molecular and serological tests enhanced the capacity to detect asymptomatic Leishmania infection in healthy individuals residing in the endemic areas of VL. A significant proportion of asymptomatic Leishmania individuals was detected in the examined endemic regions of West Bengal that might play a role in promoting VL transmission.

Optimization of loop-mediated isothermal amplification (LAMP) assays for the detection of Leishmania DNA in human blood samples

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Three systems of loop-mediated isothermal amplification (LAMP) were developed for diagnosing leishmaniasis.

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The green nucleic acid stain, SYTO-16 was adapted for monitoring the reactions in real-time.

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The LAMP assays proved highly sensitive detecting >100Fg DNA/reaction.

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Leishmania DNA was detected in a significant number of asymptomatic individuals living in endemic areas.

Visceral leishmaniasis (VL), one of the most important neglected tropical diseases, is caused by Leishmania donovani eukaryotic protozoan parasite of the genus Leishmania, the disease is prevalent mainly in the Indian sub-continent, East Africa and Brazil. VL can be diagnosed by PCR amplifying ITS1 and/or kDNA genes. The current study involved the optimization of Loop-mediated isothermal amplification (LAMP) for the detection of Leishmania DNA in human blood or tissue samples. Three LAMP systems were developed; in two of those the primers were designed based on shared regions of the ITS1 gene among different Leishmania species, while the primers for the third LAMP system were derived from a newly identified repeated region in the Leishmania genome. The LAMP tests were shown to be sufficiently sensitive to detect 0.1 pg of DNA from most Leishmania species. The green nucleic acid stain SYTO16, was used here for the first time to allow real-time monitoring of LAMP amplification. The advantage of real time-LAMP using SYTO 16 over end-point LAMP product detection is discussed. The efficacy of the real time-LAMP tests for detecting Leishmania DNA in dried blood samples from volunteers living in endemic areas, was compared with that of qRT-kDNA PCR.

Elevated Serum ADA Activity as a Marker for Diagnosis and Prognosis of Visceral Leishmaniasis and Post Kala-Azar Dermal Leishmaniasis in Indian Patients

Serum adenosine deaminase (ADA) activity increases in diseases where cellular immunity is involved. Since cell-mediated immune responses play a paramount role in the pathogenesis and healing of the visceral leishmaniasis, therefore, the present study was undertaken to evaluate the serum ADA activity in different pathological conditions. Adenosine deaminase was determined in sera of active visceral leishmaniasis (VL) patients (n = 39), active postkala-azar dermal leishmaniasis (PKDL) cases (n = 34) at the point of diagnosis and after treatment stages along with healthy controls (n = 30), endemic healthy subjects (n = 34) and endemic asymptomatic subjects (n = 34).Our in-vitro result revealed that monocytes secrete significant ADA level in response to Leishmania donovani (L.donovani) stimulation. The serum ADA activity in active VL and PKDL subjects were found to be significantly higher than that of respective treated cases and healthy controls. We also observed a marginal number (17.6%) of endemic asymptomatic subjects showed elevated serum ADA activity. Further, the ADA activity in PKDL was found to be decreased gradually during the different phases of treatment. Interestingly, 2 out of 32 treated VL cases found to have high serum ADA activity during follow up period were relapsed within few days. These results suggest the possibility of ADA as a marker of clinical pathogenesis and can be used as a surrogate marker in the diagnosis and prognosis of VL and PKDL.

Serological Assessment for Leishmania donovani Infection in Blood Donors of Sunsari District, Dharan, Nepal

Visceral leishmaniasis (VL) is a major vector-borne disease caused by Leishmania donovani, after replication of the parasites in macrophages, mononuclear phagocytic system. VL is endemic in 12 districts of central and eastern Terai lowlands of Nepal bordering North Bihar, India with an estimated 8 million population at risk. In addition, VL endemicity is also extending to new endemic regions like Dharan from its classical rural foci. Hence, we aimed to detect the evidence of Leishmania donovani infection in the blood samples received from blood donors of Sunsari district, Dharan, (eastern Nepal), a region endemic for human VL. Sera from 507 asymptomatic blood donors were subjected to serological screening for anti-Leishmania donovani antibodies. Direct agglutination test (DAT) was performed on the sera. Out of 507 donors, majority (78.50 %) were male. Among the donors, 472 (93.10 %) belonged to age group 18-45 years where as 35 (6.90 %) to age group >45 years. Circulating anti-Leishmania antibodies were detected in 5 (1 %) out of 507 healthy, Human Immunodeficiency Virus types 1 and 2 (HIV 1and 2), Hepatitis B Surface Antigen (HBsAg), anti- Hepatitis C Virus (anti-HCV)-negative, and Syphillis non-reactive donors. All the seropositive cases were male and belonged to the age group 18-45 years. The result suggests that there is an immediate need of screening asymptomatic blood donors for leishmania seropositivity especially in endemic areas.

Visceral leishmaniasis: a differential diagnosis to remember after bone marrow transplantation

Leishmania infection in immunocompromised hosts is reported in the literature, mostly concerning human immunodeficiency virus infected patients. It is not well characterized in the context of stem cell transplantation. We report a rare case clinical case of visceral leishmaniasis after allogeneic bone marrow transplantation. A 50-year-old Caucasian male was referred to allogeneic bone marrow transplantation with a high-risk acute lymphoblastic B leukemia in first complete remission. Allogeneic SCT was performed with peripheral blood stem cells from an unrelated Portuguese matched donor. In the following months, patient developed mild fluctuating cytopenias, mostly thrombocytopenia (between 60 and 80∗10⁹/L). The only significant complaint was intermittent tiredness. The common causes for thrombocytopenia in this setting were excluded—no evidence of graft versus host disease, no signs of viral or bacterial infection, and no signs of relapsed disease/dysplastic changes. The bone marrow smear performed 12 months after transplantation revealed an unsuspected diagnosis: a massive bone marrow infiltration with amastigotes.

A screen-and-treat strategy targeting visceral leishmaniasis in HIV-infected individuals in endemic East African countries: the way forward?

In the wake of the HIV epidemic, visceral leishmaniasis (VL), a disseminated protozoan infection caused by the Leishmania donovani complex, has been re-emerging, particularly in North Ethiopia where up to 40% of patients with VL are co-infected with HIV. Management of VL in HIV co-infection is complicated by increased drug toxicity, and high treatment failure and relapse rates with all currently available drugs, despite initiation of antiretroviral treatment. Tackling L. donovani infection before disease onset would thus be a logical approach. A screen-and-treat approach targeting latent or the early stage of infection has successfully been implemented in other HIV-associated opportunistic infections. While conceptually attractive in the context of VL-HIV, the basic understanding and evidence underpinning such an approach is currently lacking. Prospective cohort studies will have to be conducted to quantify the risk of VL in different risk groups and across CD4 cell count levels. This will allow developing clinical prognostic tools, integrating clinical, HIV and Leishmania infection markers. Interventional studies will be needed to evaluate prophylactic or pre-emptive treatment strategies for those at risk, ideally relying on an oral (combination) regimen. Issues like tolerability, emergence of resistance and drug interactions will require due attention. The need for maintenance therapy will have to be assessed. Based on the risk-benefit data, VL risk cut-offs will have to be identified to target treatment to those most likely to benefit. Such a strategy should be complemented with early initiation of antiretroviral treatment and other strategies to prevent HIV and Leishmania infection.

Developments in diagnosis and treatment of visceral leishmaniasis during the last decade and future prospects

Human visceral leishmaniasis (VL) continues to be a life-threatening neglected tropical disease, with close to 200 million people at risk of infection globally. Epidemics and resurgence of VL are associated with negligence by the policy makers, economic decline and population movements. Control of the disease is hampered by the lack of proficient vaccination, rapid diagnosis in a field setting and severe side effects of current drug therapies. The diagnosis of VL relied largely on invasive techniques of detecting parasites in splenic and bone marrow aspirates. rK39 and PCR, despite problems related to varying sensitivities and specificities and field adaptability, respectively, are considered the best options for VL diagnosis today. No single therapy of VL currently offers satisfactory efficacy along with safety. The field of VL research only recently shifted toward actively identifying new drugs for safe and affordable treatment. Oral miltefosine and safe AmBisome along with better use of amphotericin B have been rapidly implemented in the last decade. A combination therapy will substantially reduce the required dose and duration of drug administration and reduce the chance of the development of resistance. In addition, identification of asymptomatic cases, vector control and treatment of post-kala-azar dermal leishmaniasis would allow new perspectives in VL control and management.

Utility of the microculture method for Leishmania detection in non-invasive samples obtained from a blood bank

In recent years, the role of donor blood has taken an important place in epidemiology of Leishmaniasis. According to the WHO, the numbers of patients considered as symptomatic are only 5-20% of individuals with asymptomatic leishmaniasis. In this study for detection of Leishmania infection in donor blood samples, 343 samples from the Capa Red Crescent Blood Center were obtained and primarily analyzed by microscopic and serological methods. Subsequently, the traditional culture (NNN), Immuno-chromatographic test (ICT) and Polymerase Chain Reaction (PCR) methods were applied to 21 samples which of them were found positive with at least one method. Buffy coat (BC) samples from 343 blood donors were analyzed: 15 (4.3%) were positive by a microculture method (MCM); and 4 (1.1%) by smear. The sera of these 343 samples included 9 (2.6%) determined positive by ELISA and 7 (2%) positive by IFAT. Thus, 21 of (6.1%) the 343 subjects studied by smear, MCM, IFAT and ELISA techniques were identified as positive for leishmaniasis at least one of the techniques and the sensitivity assessed. According to our data, the sensitivity of the methods are identified as MCM (71%), smear (19%), IFAT (33%), ELISA (42%), NNN (4%), PCR (14%) and ICT (4%). Thus, with this study for the first time, the sensitivity of a MCM was examined in blood donors by comparing MCM with the methods used in the diagnosis of leishmaniasis. As a result, MCM was found the most sensitive method for detection of Leishmania parasites in samples obtained from a blood bank. In addition, the presence of Leishmania parasites was detected in donor bloods in Istanbul, a non-endemic region of Turkey, and these results is a vital importance for the health of blood recipients.

Validity of the polymerase chain reaction in the diagnosis of clinically suspected cases of American visceral leishmaniasis

To test the validity of the polymerase chain reaction for diagnosing American visceral leishmaniasis, 88 suspected cases were studied. Diagnosis was confirmed in 47 (53.5%) and ruled out in 41 (46.5%) patients. Samples of bone marrow and peripheral blood were processed by polymerase chain reaction to evaluate the sensitivity and specificity of the test and its agreement beyond chance with microscopy examination. The polymerase chain reaction was positive in bone marrow of 100% of the patients with amastigotes seen with microscopy examination, and in 59.5% in those where no parasite were seen. Agreement beyond chance between visualization of the parasite in bone marrow aspirates and polymerase chain reaction was considered weak (Kappa = 0.41). Concordance between polymerase chain reaction of bone marrow aspirates and of peripheral blood was considered excellent (Kappa = 0.88). The test turned out positive in all bone marrow aspirates of those with the disease and whereas the positivity rate was 58.5% among those without the disease, with specificity rate of 41.5%.

Evaluation of PCR procedures for detecting and quantifying Leishmania donovani DNA in large numbers of dried human blood samples from a visceral leishmaniasis focus in Northern Ethiopia

Background

Visceral Leishmaniasis (VL) is a disseminated protozoan infection caused by Leishmania donovani parasites which affects almost half a million persons annually. Most of these are from the Indian sub-continent, East Africa and Brazil. Our study was designed to elucidate the role of symptomatic and asymptomatic Leishmania donovani infected persons in the epidemiology of VL in Northern Ethiopia.

Methods

The efficacy of quantitative real-time kinetoplast DNA/PCR (qRT-kDNA PCR) for detecting Leishmania donovani in dried-blood samples was assessed in volunteers living in an endemic focus.

Results

Of 4,757 samples, 680 (14.3%) were found positive for Leishmania k-DNA but most of those (69%) had less than 10 parasites/ml of blood. Samples were re-tested using identical protocols and only 59.3% of the samples with 10 parasite/ml or less were qRT-kDNA PCR positive the second time. Furthermore, 10.8% of the PCR negative samples were positive in the second test. Most samples with higher parasitemias remained positive upon re-examination (55/59 =93%). We also compared three different methods for DNA preparation. Phenol-chloroform was more efficient than sodium hydroxide or potassium acetate. DNA sequencing of ITS1 PCR products showed that 20/22 samples were Leishmania donovani while two had ITS1 sequences homologous to Leishmania major.

Conclusions

Although qRT-kDNA PCR is a highly sensitive test, the dependability of low positives remains questionable. It is crucial to correlate between PCR parasitemia and infectivity to sand flies. While optimal sensitivity is achieved by targeting k-DNA, it is important to validate the causative species of VL by DNA sequencing.

Visceral leishmaniasis: host-parasite interactions and clinical presentation in the immunocompetent and in the immunocompromised host

Visceral leishmaniases are vector-borne parasitic diseases caused by protozoa belonging to the genus Leishmania. The heterogeneity of clinical manifestations and epidemiological characteristics of the disease reflect the complex interplay between the infecting Leishmania species and the genetic and immunologic characteristics of the infected host. The clinical presentation of visceral leishmaniasis depends strictly on the immunocompetency of the host and ranges from asymptomatic to severe forms. Conditions of depression of the immune system, such as HIV infection or immunosuppressive treatments, impair the capability of the immune response to resolve the infection and allow reactivation and relapses of the disease.

Utility of the microculture method in non-invasive samples obtained from an experimental murine model with asymptomatic leishmaniasis

The sensitivity of diagnostic methods for visceral leishmaniasis (VL) decreases because of the low number of parasites and antibody amounts in asymptomatic healthy donors who are not suitable for invasive sample acquisition procedures. Therefore, new studies are urgently needed to improve the sensitivity and specificity of the diagnostic approaches in non-invasive samples. In this study, the sensitivity of the microculture method (MCM) was compared with polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and immunofluorescent antibody test (IFAT) methods in an experimental murine model with asymptomatic leishmaniasis. Results showed that the percent of positive samples in ELISA, IFAT, and peripheral blood (PB) -PCR tests were 17.64%, 8.82%, and 5.88%, respectively, whereas 100% positive results were obtained with MCM and MCM-PCR methods. Thus, this study, for the first time, showed that MCM is more sensitive, specific, and economic than other methods, and the sensitivity of PCR that was performed to samples obtained from MCM was higher than sensitivity of the PCR method sampled by PB.

Detection of antileishmanial antibodies in blood sampled from blood bank donors in Istanbul

Aims: According to the WHO, only 5–20% of the total cases of leishmaniasis are symptomatic leishmaniasis; the other cases are identified as asymptomatic leishmaniasis. In recent studies, it has been demonstrated that donor blood plays an important role in the epidemiology of asymptomatic leishmaniasis. However, the number of the studies on this subject is still insufficient. Additionally, donor blood samples obtained from Istanbul, which is the biggest metropolitan area in Turkey, have not been investigated with regard to Leishmania. Moreover, there is no information about the sensitivity of noninvasive serological methods that are used in the detection of leishmaniasis donor blood samples. Accordingly, this study aimed to investigate the presence of antileishmanial antibodies in blood samples obtained from blood bank donors in Istanbul, by using different serologic methods, and to determine the most sensitive detection method. Materials & methods: Blood samples were taken from 188 healthy blood bank donors to the Capa Turkish Red Crescent Blood Bank (Istanbul, Turkey), and the presence of antileishmanial antibodies was measured by indirect immunofluorescent antibody test (IFAT), ELISA, immunochromatographic dipstick rapid test, and western blot (WB). Results: Antileishmanial antibodies were determined in 12 out of 188 samples by IFAT (6.4%), and six out of these 12 donors were found to be positive at diagnostic titer 1:128 (3.2%). One hundred and eighty eight samples were investigated by ELISA and one (0.5%) of them gave a positive result. None of 188 samples provided a positive result by immunochromatographic test. WB applied to the 12 seroreactive donors showed that three out of 12 donors were positive. Conclusion: In this study, the presence of antileishmanial antibodies in blood samples of blood bank donors from Istanbul has been demonstrated by using feasible and low-cost serological methods. Additionally, in comparison with other simple and low-cost detection methods, WB was used for confirmation. IFAT has a higher sensitivity and therefore may be preferred as a prescreening method in endemic or nonendemic areas.

Vaccine Development Against Leishmania donovani

Visceral leishmaniasis (VL) caused by Leishmania donovani and Leishmania infantum/chagasi represents the second most challenging infectious disease worldwide, leading to nearly 500,000 new cases and 60,000 deaths annually. Zoonotic VL caused by L. infantum is a re-emergent canid zoonoses which represents a complex epidemiological cycle in the New world where domestic dogs serve as a reservoir host responsible for potentially fatal human infection and where dog culling is the only measure for reservoir control. Life-long immunity to VL has motivated development of prophylactic vaccines against the disease but very few have progressed beyond the experimental stage. No licensed vaccine is available till date against any form of leishmaniasis. High toxicity and increasing resistance to the current chemotherapeutic regimens have further complicated the situation in VL endemic regions of the world. Advances in vaccinology, including recombinant proteins, novel antigen-delivery systems/adjuvants, heterologous prime-boost regimens and strategies for intracellular antigen presentation, have contributed to recent advances in vaccine development against VL. Attempts to develop an effective vaccine for use in domestic dogs in areas of canine VL should be pursued for preventing human infection. Studies in animal models and human patients have revealed the pathogenic mechanisms of disease progression and features of protective immunity. This review will summarize the accumulated knowledge of pathogenesis, immune response, and prerequisites for protective immunity against human VL. Authors will discuss promising vaccine candidates, their developmental status and future prospects in a quest for rational vaccine development against the disease. In addition, several challenges such as safety issues, renewed and coordinated commitment to basic research, preclinical studies and trial design will be addressed to overcome the problems faced in developing prophylactic strategies for protection against this lethal infection.

Leishmania chagasi naturally resistant to nitric oxide isolated from humans and dogs with visceral leishmaniasis in Brazil

Nitric oxide (NO) plays an important role as a leishmanicidal agent in murine macrophages. NO resistant Escherichia coli and Mycobacterium tuberculosis have been associated with poor outcomes of their resulting diseases. NO resistant Leishmania braziliensis has also been identified and exacerbates the clinical course of human leishmaniasis. We report, for the first time, natural resistance of Leishmania chagasi promastigotes to NO. These parasites were isolated from humans and dogs with visceral leishmaniasis. We also demonstrate that this resistance profile was associated with a greater survival capacity and a greater parasite burden in murine macrophages, independent of activation and after activation by IFN-γ and LPS.

Peripheral blood buffy coat smear: a promising tool for diagnosis of visceral leishmaniasis

Confirmative diagnosis of visceral leishmaniasis (VL) is still a challenge at the primary health care facilities in most of the rural areas of endemicity in the Indian subcontinent. Conventional methods for parasitological confirmation are risky and require skilled personnel, and hence they are unavailable to the poor people in the regions of endemicity. Buffy coat smear microscopy, as a minimally invasive, simple alternative for the parasitological diagnosis of VL, was evaluated in this prospective study. One hundred twelve VL patients were enrolled in this study. The buffy coat was separated from peripheral blood of all enrolled subjects using Histopaque-1119 solution. Leishman-stained buffy coat smears were examined for Leishmania donovani bodies, and buffy coat was also utilized for detection of parasite DNA by Leishmania nested PCR (LnPCR) for all cases. Concomitant splenic smears could be examined for L. donovani bodies in 66 cases, and the parasite load was graded on a scale of 1+ to 6+ for L. donovani-positive smears. All splenic smear-positive cases were also found to be positive by LnPCR. Of 112 enrolled VL cases, 103 (92%) were found to be positive for L. donovani bodies in buffy coat smear microscopy, which is promising as a confirmative diagnosis tool. We have also found a significant association of the buffy coat smear positivity with parasitic burden in the spleen smear. In this preliminary observation in Bangladesh, buffy coat smear microscopy has been found to be very simple, minimally invasive, and risk-free method of parasitological diagnosis of VL with a good diagnostic accuracy and potential for field use.

Asymptomatic infection of visceral leishmaniasis in hyperendemic areas of Vaishali district, Bihar, India: a challenge to kala-azar elimination programmes

A cohort of 91 asymptomatic individuals with visceral leishmaniasis (VL) were identified during base line screening using recombinant 39-aminoacid antigen (rk-39) and polymerase chain reaction (PCR) conducted from December 2005 to June 2006 involving 997 individuals of two highly endemic villages of Vaishali district, Bihar. The point prevalence of asymptomatic infection was 98 per 1000 persons at baseline. There was no statistically significant difference between rk-39 and PCR positivity rate (P>0.05), even though PCR positivity alone was found significantly higher (4.2%) than rk-39 positivity alone (2.6%). The monthly follow-up of the asymptomatic cohort revealed a disease conversion rate of 23.1 per 100 persons within a year. There was a statistically significant difference in conversion of disease when individuals were positive by both tests as compared to single tests by rk-39 and PCR (P<0.01). Disease conversion rate in the subjects residing in households with a history of VL (62%, 13/21) was higher than those residing in the households without a history of VL (38%, 8/21). Most of the identified asymptomatic individuals were from low socio-economic strata similar to that of VL cases in general. Apart from rk-39, PCR may be considered for screening of asymptomatic Leishmania donovani infection in large-scale epidemiological studies. Screening of asymptomatic cases and their close follow-up to ascertain early detection and treatment of VL may be considered in addition to the existing VL control strategies.

Detection of Leishmania amastigotes in peripheral blood from four dogs--Short communication

The authors carried out microscopic examination of blood smears of 1438 dogs infected with Leishmania infantum. Unusual findings of leishmaniosis associated with circulating parasitised cells are described in four dogs. Most of the dogs presented severe illness, with lethargy, dysorexia, emaciation and alterations of the haematological pattern (anaemia, thrombocytopenia, neutrophilia and monocytosis). In three cases, leishmaniosis was associated with ehrlichiosis. On examination of peripheral blood smears, Leishmania sp. amastigotes were observed both in various circulating leukocytes (neutrophil, monocyte, macrophage) and free. In conclusion, parasites can rarely be detected in blood smears (in 0.28% of the animals examined); thus, the time-consuming microscopic search for amastigotes can make only a weak contribution to the conventional diagnosis of canine leishmaniosis.

Asymptomatic infection with visceral leishmaniasis in a disease-endemic area in bihar, India

A prospective study was carried out in a cohort of 355 persons in a leishmaniasis-endemic village of the Patna District in Bihar, India, to determine the prevalence of asymptomatic persons and rate of progression to symptomatic visceral leishmaniasis (VL) cases. At baseline screening, 50 persons were positive for leishmaniasis by any of the three tests (rK39 strip test, direct agglutination test, and polymerase chain reaction) used. Point prevalence of asymptomatic VL was 110 per 1,000 persons and the rate of progression to symptomatic cases was 17.85 per 1,000 person-months. The incidence rate ratio of progression to symptomatic case was 3.36 (95% confidence interval [CI] = 0.75-15.01, P = 0.09) among case-contacts of VL compared with neighbors. High prevalence of asymptomatic persons and clinical VL cases and high density of Phlebotomus argentipes sand flies can lead to transmission of VL in VL-endemic areas.

Of cattle, sand flies and men: a systematic review of risk factor analyses for South Asian visceral leishmaniasis and implications for elimination

BACKGROUND

Studies performed over the past decade have identified fairly consistent epidemiological patterns of risk factors for visceral leishmaniasis (VL) in the Indian subcontinent.

METHODS AND PRINCIPAL FINDINGS

To inform the current regional VL elimination effort and identify key gaps in knowledge, we performed a systematic review of the literature, with a special emphasis on data regarding the role of cattle because primary risk factor studies have yielded apparently contradictory results. Because humans form the sole infection reservoir, clustering of kala-azar cases is a prominent epidemiological feature, both at the household level and on a larger scale. Subclinical infection also tends to show clustering around kala-azar cases. Within villages, areas become saturated over a period of several years; kala-azar incidence then decreases while neighboring areas see increases. More recently, post kala-azar dermal leishmaniasis (PKDL) cases have followed kala-azar peaks. Mud walls, palpable dampness in houses, and peri-domestic vegetation may increase infection risk through enhanced density and prolonged survival of the sand fly vector. Bed net use, sleeping on a cot and indoor residual spraying are generally associated with decreased risk. Poor micronutrient status increases the risk of progression to kala-azar. The presence of cattle is associated with increased risk in some studies and decreased risk in others, reflecting the complexity of the effect of bovines on sand fly abundance, aggregation, feeding behavior and leishmanial infection rates. Poverty is an overarching theme, interacting with individual risk factors on multiple levels.

CONCLUSIONS

Carefully designed demonstration projects, taking into account the complex web of interconnected risk factors, are needed to provide direct proof of principle for elimination and to identify the most effective maintenance activities to prevent a rapid resurgence when interventions are scaled back. More effective, short-course treatment regimens for PKDL are urgently needed to enable the elimination initiative to succeed.

Asymptomatic infection in family contacts of patients with human visceral leishmaniasis in Três Lagoas, Mato Grosso do Sul State, Brazil

The Brazilian city of Três Lagoas, Mato Grosso do Sul State, has experienced an urban outbreak of visceral leishmaniasis since 2000. In 2002, due to the increase in the number of cases, 46 families with cases of visceral leishmaniasis were studied to verify the prevalence of asymptomatic infection in household contacts. Indirect immunofluorescence and ELISA showed a 36.4% positive infection rate. There were no cases of symptomatic disease among these contacts. There was no statistically significant difference in gender or age. Median age was 21 years, and the 10-19-year age bracket was the most heavily affected (23%). As for family characteristics, no differences were observed in schooling or family income; most families (58.7%) owned their homes, which were built of masonry (97.8%) and had adequate infrastructure. All the families reported what were probably phlebotomine sand flies in the peridomicile. In conclusion, asymptomatic visceral leishmaniasis infection is frequent and occurs in both males and females, regardless of age.

Evidence for involvement of TNFR1 and TIMPs in pathogenesis of post-kala-azar dermal leishmaniasis

Semi-quantitative RT-PCR was exploited to analyse the intralesional cytokine gene expression in 14 post-kala-azar dermal leishmaniasis (PKDL) and 10 kala-azar (KA) patients. The data provided evidence for both inflammatory and non-inflammatory responses, as reflected by elevated tumour necrosis factor (TNF)-alpha and interleukin (IL)-10 in PKDL lesions compared with normal skin tissue (n = 6). The ratio of TNF-alpha : IL-10 message was 2.66 in PKDL cases, substantially higher than in KA (1.18). Investigation of TNF-alpha receptors (TNFR1 and TNFR2) revealed a significant down-regulation of TNFR1 transcript in both PKDL and KA compared with control. In the presence of elevated levels of TNF-alpha transcript, interference with type 1 effector activity in PKDL may be due to minimal expression of the TNFR1 gene. Investigation of matrix metalloproteinases, known to be induced by TNF-alpha, and the tissue inhibitors of matrix metalloproteinases (TIMPs), provided evidence for the roles of TIMP-1 and TIMP-3 in the pathogenesis of PKDL.

Leishmania and the leishmaniases: a parasite genetic update and advances in taxonomy, epidemiology and pathogenicity in humans

Leishmaniases remain a major public health problem today despite the vast amount of research conducted on Leishmania pathogens. The biological model is genetically and ecologically complex. This paper explores the advances in Leishmania genetics and reviews population structure, taxonomy, epidemiology and pathogenicity. Current knowledge of Leishmania genetics is placed in the context of natural populations. Various studies have described a clonal structure for Leishmania but recombination, pseudo-recombination and other genetic processes have also been reported. The impact of these different models on epidemiology and the medical aspects of leishmaniases is considered from an evolutionary point of view. The role of these parasites in the expression of pathogenicity in humans is also explored. It is important to ascertain whether genetic variability of the parasites is related to the different clinical expressions of leishmaniasis. The review aims to put current knowledge of Leishmania and the leishmaniases in perspective and to underline priority questions which 'leishmaniacs' must answer in various domains: epidemiology, population genetics, taxonomy and pathogenicity. It concludes by presenting a number of feasible ways of responding to these questions.

A rare presentation of visceral leishmaniasis without fever or splenomegaly in an elderly person

Visceral leishmaniasis (kala azar) is characterized by fever and splenomegaly in more than 80% of cases. We report a case of kala azar in an elderly person with severe anemia but no other typical features. This highlights the importance of being aware of rare presentations to avoid missing the diagnosis of this potentially fatal, but fully treatable, condition.

Comparison of new diagnostic tools for management of pediatric Mediterranean visceral leishmaniasis

New techniques are available for diagnosing leishmaniasis, but their efficacy in the identification of pediatric visceral leishmaniasis (VL) has not been compared with that of traditional methods. Blood, bone marrow, and urine samples were taken from 25 children with VL during their first clinical episode, 22 days after the start of treatment with liposomal amphotericin B (3 mg/kg/day on 6 days over a 10-day period), and when a relapse was suspected during follow-up. The results obtained suggest that antibody detection techniques, the antigen detection in urine (KAtex kit), and Leishmania nested PCR (LnPCR) analysis of the blood could be used for diagnosis of the first clinical episode. After treatment, clinical improvement was associated with negativization of Novy-MacNeal-Nicolle culture and microscopy of bone marrow aspirate, KAtex test, and LnPCR blood analysis results. Interestingly, LnPCR analysis of the bone marrow aspirate showed that sterile cure was not achieved in eight patients, two of which suffered a relapse within 10 to 20 weeks. All of the new noninvasive techniques tested showed high diagnostic sensitivity. However, LnPCR analysis of the bone marrow was the most sensitive; this test was able to detect the persistence of parasites and predict potential relapses.

Leishmania: risk to the blood supply

Leishmania infection is most often transmitted to humans via the bite of the phlebotomine sandfly, but transmission of Leishmania by transfusion has also been reported. There has been a huge increase in the incidence of cutaneous and visceral leishmaniasis in Iraq and Afghanistan. The deployment of US troops to these countries and published case reports of transmission to soldiers in endemic areas, by transfusion to infants with immature immune systems, and to individuals immunocompromised by disease or immunosuppressive therapy beckon a reexamination of blood donor deferral procedures. The length of the ongoing military conflict and the nature of exposure indicate that prior decisions regarding blood donor deferral made during the first Gulf War may no longer apply. Operation Iraqi Freedom and Operation Enduring Freedom present a much greater Leishmania threat than did Operation Desert Storm. Because most transmission by transfusion occurs in endemic areas, and visceral infection is asymptomatic in healthy individuals such as blood donors, it is difficult to determine the absolute risk of transmission by transfusion, but review of the literature provides many clues as to the appropriate measures to be taken for blood donor deferral.

Genetic susceptibility to infectious disease: lessons from mouse models of leishmaniasis

Susceptibility to infectious disease is influenced by multiple host genes, most of which are low penetrance QTLs that are difficult to map in humans. Leishmaniasis is a well-studied infectious disease with a variety of symptoms and well-defined immunological features. Mouse models of this disease have revealed more than 20 QTLs as being susceptibility genes, studies of which have made important contributions to our understanding of the host response to infection. The functional effects of individual QTLs differ widely, indicating a networked regulation of these effects. Several of these QTLs probably also influence susceptibility to other infections, indicating that their characterization will contribute to our understanding of susceptibility to infectious disease in general.

Quantification of Leishmania infantum DNA by a real-time PCR assay with high sensitivity

A real-time PCR was developed to quantify Leishmania infantum kinetoplast DNA and optimized to reach a sensitivity of 0.0125 parasites/ml of blood. In order to analyze the incidence of heterogeneity and number of minicircles, we performed comparative PCR by using the Leishmania DNA polymerase gene as a reporter. Assays performed in both promastigote and amastigote stages showed variations among different L. infantum and Leishmania donovani strains and the stability of the minicircle numbers for a particular strain. Analysis of blood samples from a patient who presented with Mediterranean visceral leishmaniasis confirmed the reliability of such an assay for Leishmania quantification in biological samples and allowed an estimation of positivity thresholds of classical tests used for direct diagnosis of the disease; positivity thresholds were in the range of 18 to 42, 0.7 to 42, and 0.12 to 22.5 parasites/ml for microscopic examination, culture, and conventional PCR, respectively. At the time of diagnosis, parasitemia could vary by a wide range (32 to 188,700 parasites/ml, with a median of 837 parasites/ml), while in bone marrow, parasite load was more than 100 parasites per 10(6) nucleated human cells. After successful therapy, parasitemia levels remain lower than 1 parasite/ml. In the immunocompromised host, relapses correlate with an increase in the level of parasitemia, sometimes scanty, justifying the need for assays with high sensitivity. Such sensitivity allows the detection of Leishmania DNA in the blood of 21% of patients with no history of leishmaniasis living in the Marseilles area, where leishmaniasis is endemic. This technique may be useful for epidemiologic and diagnostic purposes, especially for the quantification of parasitemia at low levels during posttherapy follow-up.

Visceral leishmaniasis in paediatrics

Visceral leishmaniasis is a vector-borne systemic infection, which affects half a million people each year in many areas of the world. Typical disease manifests with fever, hepatosplenomegaly, pancytopenia, and progressive deterioration of the host. Although molecular methods appear promising as a non-invasive diagnostic tool, definite diagnosis still relies on the demonstration of the parasite in tissue. Pentavalent antimonial compounds remain the mainstay of treatment worldwide, except in India. During the past decade, short courses of lipid formulations of amphotericin B were assessed and proved effective; however, their cost precludes their wide use in developing countries. Miltefosine, an oral active agent, was recently identified, and might fulfil our expectations for an effective, safe, easily administered and affordable antileishmanial treatment.