Subclinical form of the American visceral leishmaniasis

The Elimination Status of Visceral Leishmaniasis in Southeast Asia Region

PURPOSE

Visceral leishmaniasis (VL) is caused by an intracellular parasite that is transmitted to humans by sandfly bites. It is prevalent throughout Asia, Africa, the Americas, and the Mediterranean area, where 147 million people are at risk of contracting the illness. The manifestation of heterotrophic illness relies on both Leishmania implicated and the host's immunological response, ranging from asymptomatic to severe leishmaniasis with potentially lethal effects.

METHOD

We reviewed the literature (published till 31st December 2023) on the worldwide situation of leishmaniasis, standard and novel detection techniques, and traditional and modern treatment strategies and endeavors to eliminate VL. Moreover, epidemiological data was collected from the World Health Organization's publicly available databases. GraphPad Prism Version 8 was used to analyze and produce figures based on the epidemiological data.

RESULTS

Diagnosis of parasites in tissues or serology is commonly employed. Diagnosis by identifying parasite DNA using molecular techniques is becoming more popular. Despite recent findings of L. donovani resistance to pentavalent antimoniate medications, it continues to be the cornerstone in the medical management of VL. Amphotericin B and its lipid formulations, injectable paromomycin, and oral miltefosine are among the new therapy options being researched. The number of reported VL cases has reduced remarkably over the last decade due to human interventions made to eliminate VL. Particularly countries from the South East Asian region have experienced momentous progress in reducing VL cases and eliminating this disease from this region. Owing to the robust elimination programs, countries such as Bangladesh has eliminated VL as a public health concern. India and Nepal are on the verge of its elimination.

CONCLUSION

Rapid diagnosis, effective and inexpensive treatment, simple access to newly discovered medications, appropriate vector control, and a well-designed vaccine are all required for the elimination of this disease burden in impoverished areas of the globe.

Mechanism of hyperproteinemia-induced damage to female reproduction in a genetic silkworm model

Hyperproteinemia is a metabolic disorder characterized by abnormally elevated plasma protein concentrations (PPC) in humans and animals. Here, a genetic silkworm model with high PPC was employed to investigate the effect of elevated PPC on female reproduction. Transcriptomic analysis revealed that high PPC induces downregulation of the ovarian development-related genes and disrupts ovarian sugar metabolism. Biochemical and endocrinal analyses revealed that high PPC increases trehalose and glucose levels in hemolymph and glycogen content in the fat body through activation of the gluconeogenic pathway and inhibition of the Insulin/Insulin-like growth factor signaling pathway-the serine/threonine kinase (IIS-AKT) pathway, thus disrupting characteristic metabolic homeostasis of sugar in the ovary. These resulted in ovarian developmental delay as well as reduced number and poor quality of eggs. Insulin supplementation effectively increased egg numbers by lowering blood sugar. These collective results provide new insights into the mechanisms by which high PPC negatively affects female reproduction and support the potential therapeutic effects of insulin.

Evaluation of Molecular Methods to Identify Chagas Disease and Leishmaniasis in Blood Donation Candidates in Two Brazilian Centers

In Brazil, blood donation is regulated by the Brazilian Ministry of Health, and all States follow the same protocol for clinical and laboratory screening. Brazil is an endemic country for Chagas disease (CD), caused by Trypanosoma cruzi, and for leishmaniasis, caused by a species of Leishmania spp. Screening for leishmaniosis is not routinely performed by blood banks. Given the antigenic similarity between T. cruzi and Leishmania spp., cross-reactions in serological tests can occur, and inconclusive results for CD have been found. The objective of this study was to apply molecular techniques, e.g., nPCR, PCR, and qPCR, to clarify cases of blood donation candidates with non-negative serology for CD and to analyze the difference between the melting temperature during real-time PCR using SYBR Green. Thirty-seven cases that showed non-negative results for CD using chemiluminescent microparticle immunoassay (CMIA) tests from blood banks in Campo Grande, MS, and Campinas, SP, were analyzed. In the serum samples, 35 samples were evaluated by ELISA, and 24.3% (9/35) showed positive results for CD. nPCR was able to detect 12 positive results in 35 samples (34.28%). qPCR for T. cruzi was quantifiable in the samples that showed a value ≥0.002 par eq/mL (parasite equivalents per milliliter), and in 35 samples, 11 (31.42%) were positive. Of all evaluated samples using the described tests (CMIA, ELISA, nPCR, and qPCR), 18 (48.6%) were positive for CD. For MCA by qPCR, the melting temperature was 82.06 °C ± 0.46 for T. cruzi and 81.9 °C ± 0.24 for Leishmania infantum. The Mann-Whitney test showed a significant value of p < 0.0001. However, the differentiation between T. cruzi and L. infantum could not be considered due to temperature overlap. For leishmaniasis, of the 35 samples with non-negative serology for CD tested by the indirect fluorescent antibody test (IFAT), only one sample (2.85%) was positive (1:80). The PCR for Leishmania spp. was performed on 36 blood samples from donation candidates, and all were negative. qPCR for L. infantum showed 37 negative results for the 37 analyzed samples. The data presented here show the importance of performing two different tests in CD screening at blood banks. Molecular tests should be used for confirmation, thereby improving the blood donation system.

Gene Signatures of Symptomatic and Asymptomatic Clinical-Immunological Profiles of Human Infection by Leishmania (L.) chagasi in Amazonian Brazil

Individuals infected with Leishmania (L.) chagasi may present different asymptomatic and symptomatic stages of infection, which vary in the clinical–immunological profiles that can be classified as asymptomatic infection (AI), subclinical resistant infection (SRI), indeterminate initial infection (III), subclinical oligosymptomatic infection (SOI), and symptomatic infection (SI) (=American visceral leishmaniasis, AVL). However, little is known about the molecular differences between individuals having each profile. Here, we performed whole-blood transcriptomic analyses of 56 infected individuals from Pará State (Brazilian Amazon), covering all five profiles. We then identified the gene signatures of each profile by comparing their transcriptome with those of 11 healthy individuals from the same area. Symptomatic individuals with SI (=AVL) and SOI profiles showed higher transcriptome perturbation when compared to those asymptomatic III, AI and SRI profiles, suggesting that disease severity may be associated with greater transcriptomic changes. Although the expression of many genes was altered on each profile, very few genes were shared among the profiles. This indicated that each profile has a unique gene signature. The innate immune system pathway was strongly activated only in asymptomatic AI and SRI profiles, suggesting the control of infection. In turn, pathways such as MHC Class II antigen presentation and NF-kB activation in B cells seemed to be specifically induced in symptomatic SI (=AVL) and SOI profiles. Moreover, cellular response to starvation was down-regulated in those symptomatic profiles. Overall, this study revealed five distinct transcriptional patterns associated to the clinical–immunological (symptomatic and asymptomatic) profiles of human L. (L.) chagasi-infection in the Brazilian Amazon.

Asymptomatic Leishmania infection in humans: A systematic review

BACKGROUND

Leishmaniasis is a highly prevalent neglected tropical disease. It mainly presents as two forms: cutaneous and visceral leishmaniasis, the latter being the most severe form. However, asymptomatic cases of Leishmania infection result in an increase in the underreporting and transmission of the protozoan OBJECTIVES: In this study, articles on the incidence of asymptomatic Leishmania infection were systematically reviewed.

METHODS

The publications identified in the Medline/PubMed and Science Direct databases included 4568 articles. Inclusion, exclusion, and eligibility criterion analysis resulted in 83 articles being retained. These studies were mostly performed in Brazil (n = 26) and India (n = 15).

RESULTS

Several detection techniques have been used for diagnosis. Among the species found were L. infantum and L. donovani, which result in visceral leishmaniasis, and L. amazonensis, L. braziliensis, and L. panamensis. The incidence rates varied between the analyzed locations, largely due to sampling and the presence or absence of endemism in the regions. The largest populations analyzed were in two studies performed in India and Nepal. One of these studies evaluated 32,529 people and the incidence rate was 8.3% (n = 2702), while the other study evaluated 21,267 people and the incidence rate was 1.76% (n = 375). Only 14.28% of the studies investigated leishmaniasis in blood donors. Preexisting diseases have also been reported.

CONCLUSION

The findings of this systematic review present the incidence of cases of asymptomatic Leishmania infection worldwide, in addition to detailing the studies and offering information for researchers and health authorities to seek alternatives to reduce the number of leishmaniasis cases.

Visceral Leishmaniasis Urbanization in the Brazilian Amazon Is Supported by Significantly Higher Infection Transmission Rates Than in Rural Area

This was an open cohort prospective study (2016−2018) that analyzed the prevalence and incidence rates of human Leishmania (L.) infantum chagasi-infection and the evolution of their clinical-immunological profiles in distinct urban and rural scenarios of American visceral leishmaniasis (AVL) in Pará State, in the Brazilian Amazon. These infection profiles were based on species-specific DTH/IFAT-IgG assays and clinical evaluation of infected individuals, comprising five profiles: three asymptomatic, Asymptomatic Infection [AI], Subclinical Resistant Infection [SRI], and Indeterminate Initial Infection [III]; and two symptomatic, Subclinical Oligosymptomatic Infection [SOI] and Symptomatic Infection [SI = AVL]. The two distinct scenarios (900 km away) were the urban area of Conceição do Araguaia municipality and the rural area of Bujaru municipality in the southeast and northeast of Pará State. Human populations were chosen based on a simple convenience sampling design (5−10% in each setting), with 1723 individuals (5.3%) of the population (32,464) in the urban area and 1568 individuals (8.9%) of the population (17,596) in the rural one. A serological survey (IFAT-IgG) of canine infection was also performed in both scenarios: 195 dogs in the urban area and 381 in the rural one. Prevalence and incidence rates of human infection were higher in the urban area (20.3% and 13.6/100 person-years [py]) than in the rural setting (14.1% and 6.8/100-py). The AI profile was the most prevalent and incident in both urban (13.4% and 8.1/100-py) and rural (8.3% and 4.2/100-py) scenarios, but with higher rates in the former. An III profile case evolved to SOI profile after four weeks of incubation and another to SI (=AVL) after six. The prevalence of canine infection in an urban setting (39.2%) was also higher (p < 0.05) than that (32%) in the rural zone. AVL urbanization in Pará State, in the Brazilian Amazon, has led to infection rates significantly higher than those in rural sites, requiring more intense control measures.

Urine qPCR diagnoses over the entire clinical-immunological spectrum of human Leishmania (L.) infantum chagasi-infections in the Brazilian Amazon

The clinical-immunological spectrum of human Leishmania (L.) infantum chagasi-infections in the Brazilian Amazon has been defined using DTH/IFAT-IgG immune assays and the clinical statuses of infected individuals, revealing five profiles: three asymptomatic [Asymptomatic Infection (AI), Subclinical Resistant Infection (SRI), and Indeterminate Initial Infection (III)], and two symptomatic profiles [Subclinical Oligosymptomatic Infection (SOI) and Symptomatic Infection (SI = American visceral leishmaniasis/AVL)]. We evaluated the diagnostic potential of urine qPCR over the entire spectrum of infection. Resine Instagene Matrix® was used for DNA extraction from urinary sediment, with amplification carried out using SYBR® Green Taq with the RV1 and RV2 primers. We examined urine samples from 151 individuals from an endemic area of AVL in Pará State in the Brazilian Amazon, including: 91 (60.3%) with diagnoses of previous infections [13 (14.3%) sharing the AI profile, 13 (14.3%) with the SRI profile, 43 (47.2%) with III, 12 (13.2%) with SI (treated AVL), and 10 (11%) with SI (untreated AVL)]; sixty (39.7%) were DTH^(-)/IFAT-IgG^(-) (the uninfected group). The urine qPCR was positive in 61.5% of both the AI and SRI profiles, 65% of the III profile, 50% of treated AVL, 100% of untreated AVL, and 6.7% of the uninfected group. Those results confirmed the urine qPCR diagnosis in 100% of untreated AVL cases as well as in more than 60% of the cases with asymptomatic AI, SRI, and III profiles - indicating it as a promising tool for monitoring the evolution of human L. (L.) infantum chagasi-infections in endemic areas.

New record of preclinical diagnosis of American visceral leishmaniasis in Amazonian Brazil encourages optimizing disease control

The clinical-immunological spectrum of human Leishmania (L.) infantum chagasi-infection in Amazonian Brazil has recently been reviewed based on the combined use of the delayed-type hypersensitivity (DTH) and indirect fluorescence antibody test (IFAT-IgG/IgM), both with homologous L. (L.) infantum chagasi-antigens, and associated with the clinical evaluation of infected individuals. This diagnostic approach has allowed to identify the broadest clinical-immunological spectrum of human L. (L.) infantum chagasi-infection composed by five clinical-immunological profiles of infection: three asymptomatic, 1) Asymptomatic Infection (AI) [DTH^+/++++, IFAT⁻], 2) Subclinical Resistant Infection (SRI) [DTH^+/++++, IFAT^+/++], and 3) Indeterminate Initial Infection (III) [DTH⁻, IFAT^+/++], and two symptomatic ones, 4) Symptomatic Infection (SI) [=American visceral leishmaniasis - AVL] and, 5) Subclinical Oligosymptomatic Infection (SOI), both with the same immune profile [DTH⁻, IFAT^+++/++++]. Herein, we confirm for the third time the preclinical diagnosis of AVL through IgM-antibody response in an early asymptomatic case of infection (profile III), a 17-year-old boy who evolved to AVL (=profile SI) six weeks after the initial infection diagnosis, confirming that the combined use of DTH and IFAT-(IgG/IgM) assays associated with the clinical evaluation of infected individuals is potentially useful for monitoring human L. (L.) infantum chagasi-infection in endemic areas as well as optimizing AVL control.

Viability of Leishmania in blood donors: A tangible possibility of transfusion transmission

Asymptomatic individuals apparently able for blood donation, could be infected with Leishmania imposing risks for immunologically vulnerable recipients. Reverse transcribed conventional PCR targeting the 28S ribosomal subunit was conducted, in order to confirm the viability of the parasite in blood donors positive for Leishmania infection.

[Urban outbreak of leishmaniasis in Colombia]

OBJECTIVES

To describe the epidemiology, clinical characteristics and treatment of children with visceral Leishmaniasis in Neiva- Huila, from April to June 2012.

METHODOLOGY

We performed a descriptive study of an outbreak of visceral leshmaniasis in children from the urban area of Neiva.

RESULTS

There were seven cases in children younger than five years. All of them had prolonged fever, hepato-splenomegaly, severe anemia and leukopenia. Five were admitted with severe thrombocytopenia, without hemorrhagic manifestations. Six patients received first-line treatment with miltefosine, five of them had treatment failure requirirng therapy escalation to amphotericin B, two received liposomal amphotericin B and three deoxycholate amphotericin B. The main vector identified was the Lutzomyia gomezi and its main reservoir were canines.

CONCLUSION

We describe the first visceral leishmaniasis outbreak in children living in an urban area, with no mortality. Most of the cases had a good response to amphotericin B.

Identification of Leishmania donovani antigen in circulating immune complexes of visceral leishmaniasis subjects for diagnosis

The unreliability of most of the existing antibody-based diagnostic kits to discriminate between active and treated VL cases, relapse situation and reinfection are a major hurdle in controlling the cases of Kala-azar in an endemic area. An antigen targeted diagnostic approaches can be an attractive strategy to overcome these problems. Hence, this study was focused on identifying the Leishmania antigens, lies in circulating immune complex (CICs), can be used for diagnostic as well as prognostic purposes. The present study was conducted on peripheral blood samples of 115 human subjects, based on isolation of CICs. The SDS-PAGE patterns showed an up-regulated expression of 55 kDa and 23 kDa fractions in an antigens obtained from CICs of all clinical and parasitologically proven untreated visceral leishmaniasis patients before treatment (VL-BT), which ensured absolute sensitivity. However, light expressions of these bands were observed in some VL treated cases. To ascertain the prognostic value, 2D expression profiles of circulating antigens were carried out, which revealed 3 upregulated and 12 induced immunoreactive spots. Out of these, ten prominent spots were excised and subjected for enzymatic digestion to generate peptides. Mass spectrometry (MS) analysis successfully explored 20 peptides derived from kinase, kinesin, acetyl Co-A carboxylase, dynein heavy chains (cytoplasmic and axonemal/flagellar), 60S ribosomal protein, nucleoporin protein, RNA polymeraseII, protease gp63, tubulin, DNA polymerase epsilon subunit, GTP-binding protein and tyrosyl-methionyl t-RNA synthetase-like protein and 19 hypothetical protein of unknown function. Presence of L. donovani proteins in circulating antigens were further validated using anti-Ld actin and anti-α tubulin antibody. Besides, MS derived peptides confirmed its reactivity with patients' sera. Therefore, these shortlisted potential antigens can be explored as antigen-based diagnostic as well as prognostic kit.

Serum Cytokine Responses over the Entire Clinical-Immunological Spectrum of Human Leishmania (L.) infantum chagasi Infection

The clinical-immunological spectrum of human Leishmania (L.) infantum chagasi infection in Amazonian Brazil was recently reviewed based on clinical, DTH, and IFAT (IgG) evaluations that identified five profiles: three asymptomatic (asymptomatic infection, AI; subclinical resistant infection, SRI; and indeterminate initial infection, III) and two symptomatic (symptomatic infection, SI; American visceral leishmaniasis, AVL; and subclinical oligosymptomatic infection, SOI). TNF-α, IL-4, IL-6, and IL-10 serum cytokines were analyzed using multiplexed Cytometric Bead Array in 161 samples from endemic areas in the Brazilian Amazon: SI [AVL] (21 cases), III (49), SRI (19), SOI (12), AI (36), and a control group [CG] (24). The highest IL-6 serum levels were observed in the SI profile (AVL); higher IL-10 serum levels were observed in SI than in SOI or CG and in AI and III than in SOI; higher TNF-α serum levels were seen in SI than in CG. Positive correlations were found between IL-6 and IL-10 serum levels in the SI and III profiles and between IL-6 and TNF-α and between IL-4 and TNF-α in the III profile. These results provide strong evidence for associating IL-6 and IL-10 with the immunopathogenesis of AVL and help clarify the role of these cytokines in the infection spectrum.

Epidemiological aspects of vector, parasite, and domestic reservoir in areas of recent transmission and no reported human cases of visceral leishmaniasis in Brazil

About 97% of the human cases of the American visceral leishmaniasis (VL) occur in Brazil. In the last few years, the disease expanded to medium- and large-sized cities, in which surveillance and control actions have been intensified, in an effort to control VL spreading. Our two-year study was conducted in Belo Horizonte, the sixth most populous city in Brazil, which is endemic for VL. We focused in two particular districts of recent transmission of the disease, with no reported human cases and submitted to minor surveillance and control actions. Our aim was to draw an epidemiological profile of the local situation concerning Lutzomyia vector, Leishmania parasites, and the main domestic reservoirs (dogs). Lutzomyia longipalpis comprised 96.5% of the total phlebotomine sand flies captured and displayed an expressive minimal infection rate by Leishmania infantum (16.7%). Positive correlations were found between the population densities of L. longipalpis, rainfall and temperature. L. infantum was also detected in the cortelezzii complex and, for the first time, in Lutzomyia lloydi. Leishmania braziliensis, an etiological agent of the American cutaneous leishmaniasis, was also identified in L. longipalpis. Among the 1408 dogs serologically tested by standard enzyme-linked and fluorescence immune assays (ELISA/IFA) 3.6% were positive for VL. L. infantum DNA and Leishmania parasites were identified in 100% and 72.5% of the seropositive dogs, respectively. The co-positivity of other diagnostic tests for VL-Leishmania-nested PCR, imprint and myeloculture-was compared to the standard serology. Both symptomatic or asymptomatic dogs displayed an equal average number of positive diagnostic tests for VL. The districts studied display favorable conditions for the rapid spreading of human infection, in terms of L. longipalpis population density, and presence of L. infantum in both vector and main reservoir.

Preclinical diagnosis of American visceral leishmaniasis during early onset of human Leishmania (L.) infantum chagasi-infection

American visceral leishmaniasis (AVL) is an infectious disease, often with long-duration evolution, caused by Leishmania (L.) infantum chagasi. However, although the disease is considered the major clinical manifestation of the link between L. (L.) i. chagasi and the human immune response, we have recently identified five clinical-immunological profiles of infection in the Brazilian Amazon: three asymptomatic (Asymptomatic Infection--AI, Sub-clinical Resistant Infection--SRI, and Indeterminate Initial Infection--III), and two symptomatic ones [Symptomatic Infection--SI (=AVL) and Sub-clinical Oligosymptomatic Infection--SOI]. We confirm here the preclinical diagnosis of AVL through the IgM-antibody response in a case of an early infection (profile III) that evolved to the full disease after 6 weeks.

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.

Visceral leishmaniasis: A case report

Although leishmaniasis is widely prevalent in the eastern states of India namely Bihar, Jharkhand, Uttar Pradesh and West Bengal, diagnosing the illness is still difficult. We present a case of a 20-year-old agricultural labourer with a history of recurrent fever, progressive weakness and abdominal discomfort associated with loss of appetite for six months followed by petechial hemorrhages over body.On examination there was hepato-splenomegaly. A diagnosis of visceral leishmaniasis (kala-azar) was made based on the bone marrow aspiration cytology and epidemiological history of the illness. Routine blood investigations showed pancytopenia and a chest X-ray was normal. The patient was treated by intravenous administration of amphotericine B, the patient responded favourably to treatment.

Epidemiologic aspects of an emerging focus of visceral leishmaniasis in Tbilisi, Georgia

BACKGROUND

Over the last 15 years, visceral leishmaniasis (VL) has emerged as a public health concern in Tbilisi, the capital of Georgia.

METHODOLOGY/PRINCIPAL FINDINGS

Seroepidemiological surveys were conducted to determine the prevalence and incidence of infection in children and dogs within the main focus of VL, and to identify risk factors associated with human infection. Of 4,250 children investigated, 7.3% were positive by direct agglutination test in a baseline survey; an apparent incidence rate of 6.0% was estimated by one year follow-up. None of the seropositive children progressed to VL during the survey. Increased seropositivity at one year was predicted by presence at baseline of clustered flying insects (OR = 1.49; P = 0.001), perceived satisfactory sanitation (OR = 1.65; P<0.001), stray dogs (OR = 1.33; P = 0.023), and by persistent fever during the 6 months prior to baseline survey (OR = 14.2; P<0.001). Overall, 18.2% (107/588) of domestic and 15.3% (110/718) of stray dogs were seropositive by the rk39 dipstick test. Clinical VL signs were found in 1.3% of domestic and 2.9% of stray, seropositive dogs. Parasites isolated from human and dog samples were identified by PCR and phylogenetic analysis of the Leishmania 70 kDa heat-shock protein (HSP70) gene as Leishmania infantum.

CONCLUSIONS/SIGNIFICANCE

There is an active focus of L. infantum transmission in Tbilisi with a high prevalence of human and canine infections.

Risk factors for Leishmania chagasi infection in an endemic area in Raposa, State of Maranhão, Brazil

INTRODUCTION: Infection with Leishmania chagasi is the most common clinical presentation for visceral leishmaniaisis in endemic areas. The municipality of Raposa is an endemic area in State of Maranhão, Brazil, and have had registration cases of visceral leishmaniasis disease. For this reason, a cross- sectional study was conducted to evaluate the risk factors for infection with L. chagasi detected by Montenegro skin test. METHODS: The sample comprised 96% of the inhabitants of the villages of Maresia, Pantoja, and Marisol located in the municipality of Raposa, corresponding to 1,359 subjects. Data were collected using a questionnaire. Univariate and multivariate logistic regression models were applied to evaluate the association between the variables studied and infection of L. chagasi. RESULTS: The variables associated with infection upon nonadjusted analysis were a straw roof, mud walls, floors of beaten earth, presence of sand flies inside or outside of the dwelling, and bathing outdoors. Adjusted analysis showed that the presence of sand flies inside/outside the dwelling was a risk factor, and age younger than 10 years was a protective factor against asymptomatic infection. CONCLUSIONS: The results highlight the extent to which precarious living conditions of the population strengthen the epidemiological chain of visceral leishmaniasis.

Inaccuracy of enzyme-linked immunosorbent assay using soluble and recombinant antigens to detect asymptomatic infection by Leishmania infantum

BACKGROUND

One of the most important drawbacks in visceral leishmaniasis (VL) population studies is the difficulty of diagnosing asymptomatic carriers. The aim of this study, conducted in an urban area in the Southeast of Brazil, was to evaluate the performance of serology to identify asymptomatic VL infection in participants selected from a cohort with a two-year follow-up period.

METHODOLOGY

Blood samples were collected in 2001 from 136 cohort participants (97 positive and 39 negatives, PCR/hybridization carried out in 1999). They were clinically evaluated and none had progressed to disease from their asymptomatic state. As controls, blood samples from 22 control individuals and 8 patients with kala-azar were collected. Two molecular biology techniques (reference tests) were performed: PCR with Leishmania-generic primer followed by hybridization using L. infantum probe, and PCR with specific primer to L. donovani complex. Plasma samples were tested by ELISA using three different antigens: L. infantum and L. amazonensis crude antigens, and rK39 recombinant protein. Accuracy of the serological tests was evaluated using sensitivity, specificity, likelihood ratio and ROC curve.

FINDINGS

The presence of Leishmania was confirmed, by molecular techniques, in all kala-azar patients and in 117 (86%) of the 136 cohort participants. Kala-azar patients showed high reactivity in ELISAs, whereas asymptomatic individuals presented low reactivity against the antigens tested. When compared to molecular techniques, the L. amazonensis and L. infantum antigens showed higher sensitivity (49.6% and 41.0%, respectively) than rK39 (26.5%); however, the specificity of rK39 was higher (73.7%) than L. amazonensis (52.6%) and L. infantum antigens (36.8%). Moreover, there was low agreement among the different antigens used (kappa<0.10).

CONCLUSIONS

Serological tests were inaccurate for diagnosing asymptomatic infections compared to molecular methods; this could lead to misclassification bias in population studies. Therefore, studies which have used serological assays to estimate prevalence, to evaluate intervention programs or to identify risk factors for Leishmania infection, may have had their results compromised.

A cross-sectional study on the clinical and immunological spectrum of human Leishmania (L.) infantum chagasi infection in the Brazilian Amazon region

The objectives of this study were to identify individuals with symptomatic and/or asymptomatic infection due to Leishmania (L.) infantum chagasi; to study the two types of infection, both clinically and immunologically, and to determine the prevalence rate of infection at the beginning of the study. This was a cross-sectional study with a cohort of 946 individuals, of both genders, from the age of 1 year, living in the municipality of Barcarena, PA, Brazil, an area endemic for American visceral leishmaniasis (AVL). The leishmanin skin test (LST) and the indirect fluorescent test (IFAT), were used for the diagnosis of infection. One hundred and twenty cases of infection were diagnosed, with a prevalence rate of 12.6%; eight cases showed high seroreactivity (1280-10240, IgG) in IFAT and no LST reaction; four of these cases were typical AVL and four had subclinical oligosymptomatic infection. Using two immunological methods with a clinical examination of the infected individuals enabled the identification of five clinical-immunological profiles which may promote a better understanding of the interaction between L. (L.) i. chagasi and the human immune response: asymptomatic infection (AI) 73.4%; subclinical resistant infection (SRI) 15%; subclinical oligosymptomatic infection (SOI) 3%; symptomatic infection (AVL) 3% and indeterminate initial infection (III) 5%.

A longitudinal study on the transmission dynamics of human Leishmania (Leishmania) infantum chagasi infection in Amazonian Brazil, with special reference to its prevalence and incidence

This was a longitudinal study carried out during a period over 2 years with a cohort of 946 individuals of both sexes, aged 1 year and older, from an endemic area of American visceral leishmaniasis (AVL) in Pará State, Brazil. The object was to analyze the transmission dynamics of human Leishmania (Leishmania) infantum chagasi infection based principally on the prevalence and incidence. For diagnosis of the infection, the indirect fluorescent antibody test (IFAT) and leishmanin skin test (LST) were performed with amastigote and promastigote antigens of the parasite, respectively. The prevalence by LST (11.2%) was higher (p < 0.0001) than that (3.4%) by IFAT, and the combined prevalence by both tests was 12.6%. The incidences by LST were also higher (p < 0.05) than those by IFAT at 6 (4.7% x 0.6%), 12 (4.7% x 2.7%), and 24 months (2.9% x 0.3%). Moreover, there were no differences (p > 0.05) between the combined incidences by both tests on the same point surveys, 5.2%, 6.3%, and 3.6%. During the study, 12 infected persons showed high IFAT IgG titers with no LST reactions: five children and two adults developed AVL (2,560-10,120), and two children and three adults developed subclinical oligosymptomatic infection (1280-2560). The combined tests diagnosed a total of 231 cases of infection leading to an accumulated prevalence of 24.4%.

Diagnosing human asymptomatic visceral leishmaniasis in an urban area of the State of Minas Gerais, using serological and molecular biology techniques

A population-based cross-sectional study was set up in Sabará country, Southeastern Brazil, to identify asymptomatic human visceral leishmaniasis in an urban area of low disease prevalence. Blood was collected on filter paper (n=1,604 inhabitants) and examined by indirect immunofluorescent test, enzyme-linked immunosorbent assay and immunochromatographic strip test. The prevalence rates of infection ranged from 2.4 to 5.6% depending on the test used. One year later, venous blood was collected in a subset of 226 participants (102 seropositive and 124 seronegative). The tests performed were IFAT, ELISA, rk39-ELISA, polymerase chain reaction and hybridization with Leishmania donovani complex probe. No clinical signs or symptoms of leishmaniasis were observed. Using hybridization as a reference test, the sensitivity and specificity of serology were respectively: 24.8 and 71% (ELISA); 26.3 and 76.3% (rk-39); 30.1 and 63.4% (IFAT). Due to disagreements, different criteria were tested to define the infection and hybridization should be considered in epidemiological studies.

Correlation between the components of the insulin-like growth factor I system, nutritional status and visceral leishmaniasis

The role of the insulin-like growth factor I (IGF-I) system and nutritional status was studied in 241 children from a Brazilian area endemic for visceral leishmaniasis (VL). Thirty-nine children had the active form, 20 were oligosymptomatic, 38 were asymptomatic and 144 were not infected. Serum concentrations of growth hormone (GH), total and free IGF-I and IGF binding-protein 3 (IGFBP3) were measured by radioimmunoassay. Nutritional status was evaluated by anthropometric indicators and biochemical measurements. Total and free IGF-I and IGFBP3 were significantly reduced in the active form. Z scores for total and free IGF-I and for IGFBP3 were found to be significantly lower for active VL and oligosymptomatic individuals than for asymptomatic individuals, but never reached values <or=2 SD. Median values of weight-for-age Z and height-for-age Z (HAZ) scores and albumin concentration were significantly different in the active VL group compared with the other groups. Multiple discriminant analysis selected albumin and HAZ score as predictors of active and oligosymptomatic VL. The lack of correlation between auxological data and serum concentrations of the GH/IGF axis components suggested that the primary cause of retarded growth in children with active VL is not dependent on IGF-I or IGFBP3, but rather on VL intrinsic factors that might secondarily involve the GH/IGF axis.

Chemotherapy in the treatment and control of leishmaniasis

Drugs remain the most important tool for the treatment and control of both visceral and cutaneous leishmaniasis. Although there have been several advances in the past decade, with the introduction of new therapies by liposomal amphotericin, oral miltefosine and paromomycin (PM), these are not ideal drugs, and improved shorter duration, less toxic and cheaper therapies are required. Treatments for complex forms of leishmaniasis and HIV co-infections are inadequate. In addition, full deployment of drugs in treatment and control requires defined strategies, which can also prevent or delay the development of drug resistance.

Treatment options for visceral leishmaniasis

This review summarizes the current developments in therapy for visceral leishmaniasis. With the recent introduction of new drugs, the main limits in reducing deaths from visceral leishmaniasis are difficulty in diagnosis in the field and health inequality--patients lack of access to treatment. No new drugs are currently in the early stages of development. There are good reasons for the use of combination therapy; to prevent further development of resistance against the limited therapeutic options available.

Advances in leishmaniasis

Governed by parasite and host factors and immunoinflammatory responses, the clinical spectrum of leishmaniasis encompasses subclinical (inapparent), localised (skin lesions), and disseminated infection (cutaneous, mucosal, or visceral). Symptomatic disease is subacute or chronic and diverse in presentation and outcome. Clinical characteristics vary further by endemic region. Despite T-cell-dependent immune responses, which produce asymptomatic and self-healing infection, or appropriate treatment, intracellular infection is probably life-long since targeted cells (tissue macrophages) allow residual parasites to persist. There is an epidemic of cutaneous leishmaniasis in Afghanistan and Pakistan and of visceral infection in India and Sudan. Diagnosis relies on visualising parasites in tissue or serology; culture and detection of parasite DNA are useful in the laboratory. Pentavalent antimony is the conventional treatment; however, resistance of visceral infection in India has spawned new treatment approaches--amphotericin B and its lipid formulations, injectable paromomycin, and oral miltefosine. Despite tangible advances in diagnosis, treatment, and basic scientific research, leishmaniasis is embedded in poverty and neglected. Current obstacles to realistic prevention and proper management include inadequate vector (sandfly) control, no vaccine, and insufficient access to or impetus for developing affordable new drugs.