Epidemiology and ecology of leishmaniasis in Latin-America

Targeting Leishmania Promastigotes and Amastigotes Forms through Amino Acids and Peptides: A Promising Therapeutic Strategy

Millions of people worldwide are affected by leishmaniasis, caused by the Leishmania parasite. Effective treatment is challenging due to the biological complexity of the parasite, drug toxicity, and increasing resistance to conventional drugs. To combat this disease, the development of specific strategies to target and selectively eliminate the parasite is crucial. This Review highlights the importance of amino acids in the developmental stages of Leishmania as a factor determining whether the infection progresses or is suppressed. It also explores the use of peptides as alternatives in parasite control and the development of novel targeted treatments. While these strategies show promise for more effective and targeted treatment, further studies to address the remaining challenges are imperative.

Phylogenetic and biogeographical traits predict unrecognized hosts of zoonotic leishmaniasis

The spatio-temporal distribution of leishmaniasis, a parasitic vector-borne zoonotic disease, is significantly impacted by land-use change and climate warming in the Americas. However, predicting and containing outbreaks is challenging as the zoonotic Leishmania system is highly complex: leishmaniasis (visceral, cutaneous and muco-cutaneous) in humans is caused by up to 14 different Leishmania species, and the parasite is transmitted by dozens of sandfly species and is known to infect almost twice as many wildlife species. Despite the already broad known host range, new hosts are discovered almost annually and Leishmania transmission to humans occurs in absence of a known host. As such, the full range of Leishmania hosts is undetermined, inhibiting the use of ecological interventions to limit pathogen spread and the ability to accurately predict the impact of global change on disease risk. Here, we employed a machine learning approach to generate trait profiles of known zoonotic Leishmania wildlife hosts (mammals that are naturally exposed and susceptible to infection) and used trait-profiles of known hosts to identify potentially unrecognized hosts. We found that biogeography, phylogenetic distance, and study effort best predicted Leishmania host status. Traits associated with global change, such as agricultural land-cover, urban land-cover, and climate, were among the top predictors of host status. Most notably, our analysis suggested that zoonotic Leishmania hosts are significantly undersampled, as our model predicted just as many unrecognized hosts as unknown hosts. Overall, our analysis facilitates targeted surveillance strategies and improved understanding of the impact of environmental change on local transmission cycles.

Zinc and Manganese Imbalances in BALB/c Mice Experimentally Infected with Leishmania (Leishmania) amazonensis

PURPOSE

The clinical progression of Leishmania (Leishmania) amazonensis infection depends on multiple factors, including immunological status of the host and their genotypic interaction. Several immunological processes depend directly on minerals for an efficient performance. Therefore, this study used an experimental model to investigate the alterations of trace metals in L. amazonensis infection associate with clinical outcome, parasite load, and histopathological lesions, and the effect of CD4 + T cells depletion on these parameters.

METHODS

A total of 28 BALB/c mice were divided into 4 groups: 1-non-infected; 2-treated with anti-CD4 antibody; 3-infected with L. amazonensis; and 4-treated with anti-CD4 antibody and infected with L. amazonensis. After 24 weeks post-infection, levels of calcium (Ca), iron (Fe), magnesium (Mg), manganese (Mn), Cu, and Zn were determined by inductively coupled plasma optical emission spectroscopy using tissue samples of the spleen, liver, and kidneys. Additionally, parasite burdens were determined in the infected footpad (inoculation site) and samples of inguinal lymph node, spleen, liver, and kidneys were submitted to histopathological analysis.

RESULTS

Despite no significant difference was observed between groups 3 and 4, L. amazonensis-infected mice had a significant reduction of Zn (65.68-68.32%) and Mn (65.98 to 82.17%) levels. Presence of L. amazonensis amastigotes was also detected in the inguinal lymph node, spleen, and liver samples in all infected animals.

CONCLUSION

The results showed that significant alterations in micro-elements levels occur in BALB/c mice experimentally infected with L. amazonensis and may increase the susceptibility of individuals to the infection.

Histological and neuronal changes in the duodenum of hamsters infected with Leishmania (Leishmania) infantum

Visceral leishmaniasis is a neglected tropical disease caused by parasites belonging to the Leishmania genus that infect macrophages in different tissues such as the spleen, liver, lymph nodes, bone marrow, and intestine. Therefore, this study aimed to investigate the integrity of the intestinal tract and the nitrergic (NADPH-dp) and metabolically active (NADH-dp) myenteric neurons of the duodenum of golden hamsters infected with L. (L.) infantum. Therefore, thirty golden hamsters were divided into six groups (n = 5); three of them were infected with 2 × 10⁷ promastigote forms of L. (L.) infantum by intraperitoneal route (Infected Group - IG) and three were inoculated with saline solution (control group - CG). After 30, 60 and 90 days post-infection (DPI) infected animals were euthanized and the liver, spleen and duodenum were collected to analyze tissue parasitism. The duodenum was processed using usual histological techniques to analyze the main changes that occurred during infection and histochemical techniques to phenotype myenteric neurons. Amastigote forms were observed in the spleen, liver, and duodenum during all experimental periods, and tissue parasitism in these organs increased significantly over time. At 30 DPI, reduction in muscle tunic, increase in the total intestinal wall and the number of goblet cells PAS+ was observed. At 60 DPI, an increase in intestinal crypts and intraepithelial lymphocytes was observed, and a reduction in intestinal villi was observed at 90 DPI, along with an increase in crypt size. Regarding neurons, an increase in the density of the NADPH-dp population was observed at 30 DPI, but at 60 and 90 DPI a significant reduction of this population was observed. In general, infection progression was observed to cause significant morphofunctional changes in the duodenum of infected hamsters.

India's performance in controlling Visceral Leishmaniasis as compared to Brazil over past three decades: findings from global burden of disease study

Visceral leishmaniasis (VL) is a neglected tropical disease which contributes to the mortality and morbidity significantly in India and Brazil. This study was planned to compare the trends of incidence, prevalence, death and disability-adjusted life years (DALY) of VL burden in India and Brazil from 1990 to 2019 using Global burden of disease study (GBD) data. The metrics are presented as age-standardized rates per 100,000 inhabitants with their respective uncertainty intervals (95% UI) and relative percentages of change. The decline in the Incidence rate is more in case of India (16.82 cases per 100,000 in 1990 to 0.60 cases in 2019) as compared to Brazil (3.12 cases per 100,000 in 1990 to 2.65 cases in 2019). The annualized rate of change in number of prevalent cases for India is - 0.95 (95% UI - 0.98 to - 0.91) whereas for Brazil it is - 0.06 (95% UI - 0.41 to 0.52). The annualized rate of change in number of DALY for India is - 0.94 (95% UI - 0.96 to - 0.92) whereas for Brazil it is - 0.09 (95% UI - 0.25 to 0.28). The annualized rate of change in number of deaths for India is - 0.93 (95% UI - 0.95 to - 0.92) whereas for Brazil it is increasing i.e. 0.04 (95% UI - 0.12 to 0.51). India achieves significant reduction in the age standardized incidence, prevalence, mortality and DALY of VL as compared to Brazil during the period of 1990 to 2019. A multi-centric study is required to assess bottleneck in the existing strategies of VLSCP in Brazil.

Piper aduncum essential oil: a promising insecticide, acaricide and antiparasitic. A review

Several studies have assessed the potential of essential oils as substitutes for synthetic pesticides, in order to counter insect resistance to commercial pesticides. Piper aduncum L. is a very common shrub in the Amazon Rainforest and in other subtropical areas. The objective of this review was to analyse the existing information on P. aduncum essential oil as a raw material for new bioproducts for sustainable pest disease management. With this review, we collected and critically analysed 59 papers, representing all the studies that aimed to evaluate the essential oil properties of this species as an insecticide, acaricide and antiparasitic. The chemical composition differs depending on the origin, although phenylpropanoid dillapiole is the most cited component, followed by myristicin, 1,8-cineole and β-ocimene. Between the acaricidal, antiparasitic and synergistic activities, the insecticidal effects are highly promising, with optimal results against the malaria vector Aedes aegypti, with an LC50 that ranges between 57 and 200μg/mL. Acaricidal activity has mainly been reported against Tetranychus urticae, showing an LC50 that ranges between 5.83 and 7.17μg/mL. Antiparasitic activity has predominately been found on Leishmania amazonensis, and antipromastigote activity has been found to be between 23.8 and 25.9μg/mL. Concerning the synergistic effect between dillapiole and synthetic insecticides, four studies on Spodoptera frugiperda found promising results with cypermethrin. In this review, we highlighted the potential of P. aduncum essential oil as a biopesticide, also focusing on the lack of information about applied research. We also provide suggestions for future investigations.

Immune response dynamics and Lutzomyia longipalpis exposure characterize a biosignature of visceral leishmaniasis susceptibility in a canine cohort

Background

Reports have shown correlations between the immune response to vector saliva and Leishmaniasis outcome. We followed dogs in an endemic area for two years characterizing resistance or susceptibility to canine visceral leishmaniasis (CVL) according to Leishmania infantum diagnosis and clinical development criteria. Then, we aimed to identify a biosignature based on parasite load, serum biological mediators’ interactions, and vector exposure intensity associated with CVL resistance and susceptibility.

Methodology/Principal findings

A prospective two-year study was conducted in an area endemic for CVL. Dogs were evaluated at 6-month intervals to determine infection, clinical manifestations, immune profile, and sandfly exposure. CVL resistance or susceptibility was determined upon the conclusion of the study. After two years, 78% of the dogs were infected with L. infantum (53% susceptible and 47% resistant to CVL). Susceptible dogs presented higher splenic parasite load as well as persistence of the parasite during the follow-up, compared to resistant ones. Susceptible dogs also displayed a higher number of correlations among the investigated biological mediators, before and after infection diagnosis. At baseline, anti-saliva antibodies, indicative of exposure to the vector, were detected in 62% of the dogs, reaching 100% in one year. Higher sandfly exposure increased the risk of susceptibility to CVL by 1.6 times (CI: 1.11–2.41). We identified a discriminatory biosignature between the resistant and susceptible dogs assessing splenic parasite load, interaction of biological mediators, PGE₂ serum levels and intensity of exposure to sandfly. All these parameters were elevated in susceptible dogs compared to resistant animals.

Conclusions/Significance

The biosignature identified in our study reinforces the idea that CVL is a complex multifactorial disease that is affected by a set of factors which are correlated and, for a better understanding of CVL, should not be evaluated in an isolated way.

Visceral Leishmaniasis (VL) is a disease that can affect humans and dogs, caused by a parasite called Leishmania transmitted through the bite of sandfly insects. During the bite, together with the parasite, the insects also inoculate their saliva into the host. The host immune response produces molecules to the sandfly saliva, such as antibodies and cytokines that can impact VL resistance or susceptibility. The presence of these molecules also indicates if the insects bit the hosts. We followed dogs of a VL endemic area for two years to study Canine Visceral Leishmaniasis (CVL) and immune response to sandfly saliva. Dogs were evaluated at 6-month intervals to determine Leishmania infection, clinical manifestations, parasite load, immune response, and sandfly exposure. CVL resistance or susceptibility was determined upon the conclusion of the study. Dogs living in the endemic area were intensely bitten, as at the beginning of the study, 62% of the dogs present anti-saliva antibodies, reaching 100% after one year. Our findings revealed a biosignature of CVL susceptibility characterized by elevated parasite load, interaction of cytokines, and higher exposure to the sandfly. This data reinforced that CVL is a complex disease affected by several factors related to each other.

Structural basis for guide RNA trimming by RNase D ribonuclease in Trypanosoma brucei

Infection with kinetoplastid parasites, including Trypanosoma brucei (T. brucei), Trypanosoma cruzi (T. cruzi) and Leishmania can cause serious disease in humans. Like other kinetoplastid species, mRNAs of these disease-causing parasites must undergo posttranscriptional editing in order to be functional. mRNA editing is directed by gRNAs, a large group of small RNAs. Similar to mRNAs, gRNAs are also precisely regulated. In T. brucei, overexpression of RNase D ribonuclease (TbRND) leads to substantial reduction in the total gRNA population and subsequent inhibition of mRNA editing. However, the mechanisms regulating gRNA binding and cleavage by TbRND are not well defined. Here, we report a thorough structural study of TbRND. Besides Apo- and NMP-bound structures, we also solved one TbRND structure in complexed with single-stranded RNA. In combination with mutagenesis and in vitro cleavage assays, our structures indicated that TbRND follows the conserved two-cation-assisted mechanism in catalysis. TbRND is a unique RND member, as it contains a ZFD domain at its C-terminus. In addition to T. brucei, our studies also advanced our understanding on the potential gRNA degradation pathway in T. cruzi, Leishmania, as well for as other disease-associated parasites expressing ZFD-containing RNDs.

Major environmental and socioeconomic determinants of cutaneous leishmaniasis in Brazil - a systematic literature review

Cutaneous leishmaniasis (CL) is a zoonotic disease with complex transmission cycle. Some environmental and socioeconomic factors are known to be the major determinants of the transmission process, which are involved in configuring the spatiotemporal patterns and thus can be delimiting. However, the relevance of these socioeconomic and environmental determinants is still not well understood. In this study, we aimed to identify the major environmental and socioeconomic determinants of CL in Brazil by articulating a systematic literature review of studies that are based on this subject. The methodology included a search for studies according to a structured protocol using the scientific platforms, such as Scielo and PubMed. The references of each identified article were who referred to CL determinants were further screened, and so on. We extracted information from 41 articles and the determinants were grouped accordingly. Two measures were evaluated as follows: a) the frequency of citations of the determinants; and b) the proportion of determinants identified as having "significant association in analytical studies" with respect to the total number of determinants analyzed in other analytical studies using the same concept. The analyzed articles covered most of the regions of Brazil and 7 other countries bordering Brazil. We found 43 concepts of determinants. However, the final selection resulted in the identification of 14 major determinants. These results therefore contribute in the identification of major CL determinants and this information can be used to establish strategies for identifying risk prone areas for disease surveillance.

Natural Leishmania (Leishmania) mexicana infection and biting activity of anthropophilic sand fly Lutzomyia ayacuchensis in the Ecuadorian Andes

To elucidate the transmission mode of Andean cutaneous leishmaniasis (Andean-CL), natural Leishmania infection and biting activity of sand flies were tested in a selected sylvatic focus of the endemic area of the Ecuadorian Andes. Monthly sand fly collections and dissections were conducted during 12 months from July 2018 to June 2019. The Leishmania positive specimens/slides with innumerable amounts of actively mobile flagellates made us easy to detect positive sand flies. The promastigotes observed located in the anterior and posterior midgut, without the hindgut localization. The parasite isolated was identified as L. (L.) mexicana by cytochrome b gene analysis. No other Leishmania or flagellate species parasitic in sand flies was observed in the area. Only Lu. ayacuchensis was caught throughout. Monthly microscopic examination of Lu. ayacuchensis revealed 0.75-8.33% of natural L. (L.) mexicana infection rates. Higher Leishmania infection months were present at the end of the wet season of the Andes, while higher sand fly numbers occurred during the dry season. Diurnal biting (blood meal seeking) activity of sand flies started around 17:30 before sunset, increased between 18:00 and 19:30, and thereafter decreased drastically probably because of low temperature (15-18 °C) in the area. The results provide information important for the planning of vector control strategy and management of the disease in the Andean-CL endemic area of Ecuador.

Seroprevalence, Clinical, and Pathological Characteristics of Canine Leishmaniasis in a Central Region of Colombia

Introduction

Leishmaniasis is a zoonotic disease which is caused by protozoan parasites of the genus Leishmania. Canids are the most important reservoir of the parasites; however, limited data are available on the species of Leishmania prevalent in these animals and their impact on human health. The objective of this study was to estimate the seroprevalence of leishmaniasis in dogs from an inter-Andean region of Colombia during July 2016–July 2017, and to describe the clinical and histopathological features of the disease.

Material and Methods

A total of 155 dogs were subjected to clinical examination and a serological test for detection of antibodies against Leishmania. Necropsy was carried out on positive animals and tissue samples were processed by routine histopathology.

Results

Altogether 19 dogs were positive in the serological test, establishing a 12% seroprevalence of Leishmania. Clinical examination and necropsy revealed exfoliative and ulcerative dermatitis with haemorrhagic borders on the ears, head, nose, and legs. Histopathology revealed severe multifocal dermatitis with abundant Leishmania amastigotes within the cytoplasm of phagocytic cells, depletion of lymphocytes in lymphoid tissues, interstitial pneumonia, and interstitial nephritis. Tissue samples were positive for Leishmania by PCR.

Conclusion

The macro- and microscopic changes correlated with the presence of Leishmania as established by serological test and PCR.

What makes mucosal and anergic diffuse cutaneous leishmaniases so clinically and immunopathogically different? A review in Brazil

American cutaneous leishmaniasis (ACL) is a parasitic protozoan disease caused by different Leishmania species widely distributed throughout Latin America. Fifteen Leishmania species belonging to the subgenera Viannia, Leishmania and Mundinia are known to cause ACL. Seven of these species are found in Brazil, of which Leishmania (Viannia) braziliensis and Leishmania (Leishmania) amazonensis have the highest potential to cause mucosal (ML) and anergic diffuse cutaneous leishmaniasis (DCL), respectively, the most severe forms of ACL. The clinical and immunopathological differences between these two clinical forms are reviewed here, taking into account their different physiopathogenic mechanisms of dissemination from cutaneous lesions to mucosal tissues in the case of ML and to almost all body surfaces in the case of anergic DCL. We also discuss some immunopathogenic mechanisms of species-specific Leishmania antigens (from the subgenera Viannia and Leishmania) that are most likely associated with the clinical and immunopathological differences between ML and anergic DCL. Those discussions emphasize the pivotal importance of some surface antigens of L. (V.) braziliensis and L. (L.) amazonensis, such as lipophosphoglycan, phosphatidylserine and CD200 (an immunoregulatory molecule that inhibits macrophage activation), that have been shown to exert strong influences on the clinical and immunopathological differences between ML and anergic DCL.

Vector Preference Annihilates Backward Bifurcation and Reduces Endemicity

We propose and analyze a mathematical model of a vector-borne disease that includes vector feeding preference for carrier hosts and intrinsic incubation in hosts. Analysis of the model reveals the following novel results. We show theoretically and numerically that vector feeding preference for carrier hosts plays an important role for the existence of both the endemic equilibria and backward bifurcation when the basic reproduction number [Formula: see text] is less than one. Moreover, by increasing the vector feeding preference value, backward bifurcation is eliminated and endemic equilibria for hosts and vectors are diminished. Therefore, the vector protects itself and this benefits the host. As an example of these phenomena, we present a case of Andean cutaneous leishmaniasis in Peru. We use parameter values from previous studies, primarily from Peru to introduce bifurcation diagrams and compute global sensitivity of [Formula: see text] in order to quantify and understand the effects of the important parameters of our model. Global sensitivity analysis via partial rank correlation coefficient shows that [Formula: see text] is highly sensitive to both sandflies feeding preference and mortality rate of sandflies.

Effectiveness of the Brazilian Visceral Leishmaniasis Surveillance and Control Programme in reducing the prevalence and incidence of Leishmania infantum infection

Background

Control strategies adopted by the Brazilian Visceral Leishmaniasis Surveillance and Control Programme (VLSCP) include identifying and culling seropositive infected dogs, early diagnosis and treatment of human cases, chemical control of the vector and population awareness. This study evaluated the effectiveness of the VLSCP on the prevalence and incidence rates of Leishmania infantum in children residing in areas under different VLSCP intervention times.

Methods

A quasi-experimental epidemiological study with a panel (two cross-sectional) and a concurrent cohort was performed in three areas of Belo Horizonte, southeast Brazil. The first cross-sectional study (I) was carried out with 1875 children, 478 of which were enrolled in the cohort study. In the second cross-sectional study (II), 413 additional children were included, totalizing 891 children. Laboratory diagnosis was performed by ELISA-rK39. Analyses included multilevel logistic and Poisson regression models.

Results

The incidence rates of L. infantum infection were: 14.4% in the area where VLSCP intervention was initiated in 2006 (AI2006); 21.1% in the area where intervention was initiated in 2008 (AI2008); and 11.6% in the area where intervention was initiated in 2010 (AI2010 - control area). A follow-up period of 24 months showed that the persons-time incidence rates in AI2006, AI2008, and AI2010 were: 6.2/100, 10/100, and 5.6/100 persons/24 months, respectively. The final prevalence rates of infection (cross-sectional II - in 2012), compared to the initial rates (cross-sectional I - in 2010), increased 83.7% in AI2006, 74.1% in AI2008, and decreased 5% in AI2010. Analysis of the effectiveness revealed that children residing in AI2008 are more likely to be infected (OR = 1.84; 95% CI: 1.06-3.23) and present a higher risk of infection (IRR = 1.76; 95% CI: 1.05-2.95) compared to those in AI2010. No statistically significant differences were observed in asymptomatic infection (OR and IRR) in AI2006 compared to AI2010.

Conclusions

The VLSCP was not effective at controlling L. infantum infection in areas where interventions had respectively been carried out for six and four years. However, it is unclear what the consequences in terms of human infection and diseases would be in the absence of the VLSCP. Efforts to improve the effectiveness of control measures remain a necessary priority.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3166-0) contains supplementary material, which is available to authorized users.

Burden of leishmaniasis in Brazil and federated units, 1990-2016: Findings from Global Burden of Disease Study 2016

BACKGROUND

The study presents estimates for the burden of visceral leishmaniasis (VL) and cutaneous and mucocutaneous leishmaniasis (CML) in Brazil and its 27 federated units using data from the Global Burden of Disease Study (GBD) 2016.

METHODOLOGY

We report the incidence, years of life lost (YLL), years lived with disability (YLD), and disability-adjusted life years (DALY) for leishmaniasis in Brazil from 1990 to 2016. The metrics are presented as age-standardized rates per 100,000 inhabitants with their respective uncertainty intervals (95%UI) and relative percentages of change.

PRINCIPAL FINDINGS

The age-standardized incidence rate of leishmaniasis decreased 48.5% from 1990 (71.0, 95%UI 24.3-150.7) to 2016 (36.5, 95%UI 24.7-50.9), whereas the age-standardized DALY increased 83.6% over the studied period from 12.2 (95%UI 7.9-18.8) to 22.4 (95%UI 13.3-36.2). The age-standardized incidence rate and YLL for VL increased by 52.9% and 108% from 1990 to 2016, respectively. Considering CML, the age-standardized incidence rate and YLD decreased by 51% and 31.8% respectively for the same period. For VL, similar profiles for male and female were observed, with YLL and DALY increasing over time; with males presenting slightly higher values. The highest YLL rates were among "under 1-year old" children, which increased 131.2% from 1990 to 2016. Regarding CML, the highest values of YLD and DALY were verified among males, and YLD values showed a similar profile, with rates increasing with age. The VL burden increased in some states in the Northeast and Southeast regions and decreased for CML in some Northern states.

CONCLUSION

The increase of VL burden over the study period might be associated with the difficulties in controlling the disease spread. Information regarding the weight of VL and CML, including the death and disability tolls that they cause, highlights the impact of these neglected diseases on public health and the importance of effective prevention and treatment.

Behavior of two Leishmania infantum strains-evaluation of susceptibility to antimonials and expression of microRNAs in experimentally infected J774 macrophages and in BALB/c mice

Strains of the same Leishmania parasite species, isolated from different host organisms, may exhibit unique infection profiles and induce a change in the expression of microRNAs among host macrophages and in model host mice. MicroRNAs (MiR) are endogenous molecules of about 22 nucleotides that are involved in many regulatory processes, including the vertebrate host immune response. In this respect, the infectivity and susceptibility to antimonials of two L. infantum strains, BH46, isolated from human, and OP46, isolated from symptomatic dog, were characterized in J774 macrophages and BALB/c mice. Parasite burden was assessed in the liver, spleen, and bone marrow using the serial limiting dilution technique. A higher parasite burden was observed in the spleen and bone marrow of animals infected with OP46 compared to BH46 strain. Our results also showed that OP46 was less susceptible to the antimonials. In addition, miR-122 and miR-155 expression was evaluated in the liver and J774 macrophages, and in spleens from infected animals, respectively. An increase was observed in the expression of miR-155 in J774 macrophages infected with both strains compared to uninfected cells, with a higher expression in cells infected with OP46. However, no difference in the expression of miR-122 and miR-155 was observed in the infected animals. Thus, this study shows that OP46 was more infective for mice, it caused a higher increase in miR-155 expression in infected macrophages and was less susceptible to the antimonials evaluated. These data suggest that alteration in miR-155 level likely plays a role in regulating the response to L. infantum.

Cost-effectiveness of liposomal amphotericin B in hospitalised patients with mucocutaneous leishmaniasis

OBJECTIVE

To compare the cost-effectiveness of L-AmB with that of Sb^V and AmB-D, for the treatment of mucocutaneous leishmaniasis in a hospital in north-east Brazil.

METHODS

We developed an economic model based on retrospective data of 73 hospitalised patients in 2006-2012, from hospital and public health system perspectives.

RESULTS

In the economic model, 82.2% of patients who started treatment with L-AmB had completed it after 2 months, vs. 22.0% for the Sb^V and 19.9% for the AmB-D groups. After 12 months of follow-up, these proportions were 100% in the L-AmB, 77.4% in the AmB-D and 72.2% in the Sb^V group. Markov chain analyses showed that the group that started therapy with Sb^V had the lowest mean total cost (US$ 3782.38), followed by AmB-D (US$ 5211.27) and L-AmB (US$ 11 337.44). The incremental cost-effectiveness ratio for L-AmB was US$ 18 816.23 against Sb^V and US$ 24 504.65 against AmB-D. In the sensitivity analysis, the drug acquisition cost of L-AmB significantly influenced the results.

CONCLUSIONS

In the treatment of mucocutaneous leishmaniasis, L-AmB is a cost-effective alternative to Sb^V and AmB-D owing to its higher effectiveness, safety and shorter course.

Considerations of potential vectors and animal reservoirs in an emerging cutaneous leishmaniasis area in São Domingos ranch, Paraná State in Southearn Brazil

The aim of this study was to better understand the dynamics of Leishmania sand flies and reservoirs in São Domingos ranch, Arapongas municipality, Paraná State, an anthropic environment in an endemic area of cutaneous leishmaniasis (CL). Sand flies were collected in wild animal burrows, residences and in the forest, with Falcão light trap (FA), Shannon trap (SH) and quadrangular pyramidal trap (QP). The search for Leishmania was made on sand flies, biological samples of wild rodents and dogs using PCR and culture; while parasite direct search (DS) was carried out on animal skin lesions; infection of gold hamsters; and indirect immunofluorescence (IIF) test in dog blood samples. Eighty eight (88) sand flies were collected with FA traps and 526 sand flies using the SH trap, with a predominance of Pintomyia fischeri. Six hundred and one (601) specimens of Brumptomyia brumpti were collected in armadillo burrows, with the QP trap. Seventeen (17) wild rodents were captured, six of them had skin lesions with characteristics of Leishmania infection. Even though no positive test was found for Leishmania, epidemiological surveillance should be maintained, remembering that the human buildings are situated only 50 m from the forest. Considering the species of wild animals and sandflies found in São Domingos, the negative test found do not exclude the existence of the Leishmania transmission cycle in this preservation area.

Investigation of the Anti-Leishmania (Leishmania) infantum Activity of Some Natural Sesquiterpene Lactones

Leishmaniases are neglected infectious diseases caused by parasites of the ‘protozoan’ genus Leishmania. Depending on the parasite species, different clinical forms are known as cutaneous, muco-cutaneous, and the visceral leishmaniasis (VL). VL is particularly fatal and the therapy presents limitations. In the search for new anti-leishmanial hit compounds, seven natural sesquiterpene lactones were evaluated against promastigotes and intracellular amastigotes of Leishmania (Leishmania) infantum, a pathogen causing VL. The pseudoguaianolides mexicanin I and helenalin acetate demonstrated the highest selectivity and potency against intracellular amastigotes. In addition, promastigotes treated with helenalin acetate were subject to an ultrastructural and biochemical investigation. The lethal action of the compound was investigated by fluorescence-activated cell sorting and related techniques to detect alterations in reactive oxygen species (ROS) content, plasma membrane permeability, and mitochondrial membrane potential. Helenalin acetate significantly reduced the mitochondrial membrane potential and the mitochondrial structural damage was also confirmed by transmission electron microscopy, displaying an intense organelle swelling. No alteration of plasma membrane permeability or ROS content could be detected. Additionally, helenalin acetate significantly increased the production of nitric oxide in peritoneal macrophages, probably potentiating the activity against the intracellular amastigotes. Helenalin acetate could hence be a useful anti-leishmanial scaffold for further optimization studies.

Yadón Z, Idali Saboyá Díaz M, de Fátima de Araújo Lucena F, Gerardo Castellanos L, J. Sanchez-Vazquez M. Exploring Spatial and Temporal Distribution of Cutaneous Leishmaniasis in the Americas, 2001-2011

Leishmaniasis is an important health problem in several countries in the Americas and cases notification is limited and underreported. In 2008, the Pan American Health Organization (PAHO/WHO) met with endemic countries to discuss the status and need of improvement of systems region-wide. The objective is to describe the temporal and spatial distribution of cutaneous leishmaniasis (CL) cases reported to PAHO/WHO by the endemic countries between 2001 and 2011 in the Americas.

In the Americas, cutaneous leishmaniasis (CL) cases are notified across a wide geographic area, extending from southern United States to northern Argentina. Currently, 70–75% of all estimated cases of CL worldwide occur in ten countries, including four in the Americas (Brazil, Colombia, Nicaragua, and Peru) and six countries from Africa and the Eastern Mediterranean. This study shows the epidemiological situation and geographical distribution of CL cases reported by passive surveillance system of endemic countries of the American Region from 2001 to 2011, collected and consolidated by the Pan American Health Organization (PAHO). Furthermore, it represents a joint effort of the National Programs of leishmaniases. Despite some limitations, the data were analyzed and discussed and this study represents the first step to understand the global epidemiological situation in this Region and it contributes to the improvement of the surveillance of leishmaniases in the Americas.

Risk Factors Associated with Human Visceral Leishmaniasis in an Urban Area of Bahia, Brazil

BACKGROUND

The early diagnosis of asymptomatic, acute, and subclinical Leishmania infections remains a challenge for controlling visceral leishmaniasis (VL). Individuals with acute VL represent <1% of Leishmania infections occurring in active transmission endemic areas. In this cross-sectional study with a prospective follow-up, we explored the risk factors associated with acquisition of Leishmania infection in an area with newly identified endemic VL.

MATERIALS AND METHODS

Ninety-four households were randomly selected from the study area, which included a population of 213 individuals (10% of the total population of Pé de Areia, Bahia, Brazil). Clinical and epidemiological surveys were prospectively performed to detect cases of asymptomatic infections, acute VL, and subclinical VL, using the leishmanin skin test (LST), and serological response to two Leishmania-specific antigens: rK39 and rK26.

RESULTS

Within the 92 households included in the study, the prevalence of Leishmania infection in individuals detected by positive serology was 91/197 (46.2%; 95% CI: 0.3937-0.5316) and by LST was 29/114 (25.4%; 95% CI: 0.1834-0.3414). Reactivity to both antigens was detected in 64/197 individuals (32.5%; 95% CI: 0.2634-0.3931). Among 89 individuals diagnosed with leishmaniasis, we found acute VL in one (1%), subclinical VL in 20 (22.5%), and asymptomatic Leishmania infection in 68 (76.4%) subjects. Use of repellents and bed nets showed no significant protection (prevalence ratio [PR] = 1.01, p = 1.0). Interestingly, individuals residing in houses with a sand backyard had significant protection against Leishmania infection (PR = 1.24, p = 0.049) compared to those with a different type or no backyard. Moreover, the presence of cat or dog at home was also not a risk factor (dog: PR = 1.14, 95% CI: 0.80-1.64; and cat: PR = 1.19, 95% CI: 0.78-1.81). We conclude that in newly discovered areas of transmission of L. infantum infection with sylvatic reservoirs, periodic surveys may be helpful in identifying risk factors for infection and optimizing prevention guidelines.

New Approaches to Systematics of Trypanosomatidae: Criteria for Taxonomic (Re)description

While dixenous trypanosomatids represent one of the most dangerous pathogens for humans and domestic animals, their monoxenous relatives have frequently become model organisms for studies of diversity of parasitic protists and host-parasite associations. Yet, the classification of the family Trypanosomatidae is not finalized and often confusing. Here we attempt to make a blueprint for future studies in this field. We would like to elicit a discussion about an updated procedure, as traditional taxonomy was not primarily designed to be used for protists, nor can molecular phylogenetics solve all the problems alone. The current status, specific cases, and examples of generalized solutions are presented under conditions where practicality is openly favored over rigid taxonomic codes or blind phylogenetic approach.

Ecological Determinants of Forest to the Abundance ofLutzomyia longiflocosain Tello, Colombia

Lutzomyia longiflocosais considered the most likely vector of cutaneous leishmaniasis in the sub-Andean region of the upper valley of the Magdalena River between 1,000 and 2,000 meters in the Department of Huila, Colombia.L. longiflocosais anthropophilic, has endophagic behavior, and is especially important since its dominance in epidemics recorded in the last decade in the departments of Huila, Tolima, and the outbreak in Norte de Santander. The aim of our work is to identify ecological determinants in forest microhabitat level defining the abundance ofL. longiflocosa. We use sampling; this was performed in 56 microhabitats of 28 forests with CDC traps for two consecutive nights from 18:00 to 06:00 hours. Each microhabitat (favorable and unfavorable) was located 10 m from the ecotone, with an approximate area of 10 m2. Thirty-five variables were examined as potential explanatory variables which were recorded in each microhabitat. Regression models were used to identify ecological determinants. Our results confirm that there are favorable microhabitats in the forest with specific ecological determinants that define the aggregated distribution of the species and provide the conditions necessary for survival and abundance ofL. longiflocosa.

Serological survey of Leishmania infection in blood donors in Salvador, Northeastern Brazil

BACKGROUND

Visceral Leishmaniasis is endemic to Brazil, where it is caused by Leishmania infantum (syn. Leishmania chagasi). Following parasite inoculation, individuals may experience asymptomatic infection, raising the possibility of parasite transmission through the transfusion of contaminated blood products. In the present work, we evaluated the prevalence of asymptomatic Leishmania infection among blood donors in Salvador, northeastern Brazil.

METHODS

Peripheral blood was collected from 700 blood donors attending the Blood Bank of Bahia (HEMOBA/SESAB), from January to September 2010. We evaluated anti-Leishmania serology by ELISA, employing Soluble Leishmania Antigen (sensitivity 90% and specificity 95%). The presence of parasite DNA was determined by qPCR, targeting a single copy gene (G6PD), and by end-point PCR, targeting multiple targets, namely a segment located in the Leishmania rRNA locus (ITS) and the conserved region of kinetoplastid DNA (kDNA) minicircles.

RESULTS

The blood-donor population was comprised of 74.5% of males with a mean age of 34 years. Anti-Leishmania serology by ELISA was positive in 5.4% (38/700) individuals. One individual was also positive for Chagas' disease and another tested positive for Syphilis. Employing qPCR, parasite DNA was not found in any of 38 seropositive samples. However, by ITS PCR, 8/38 (21%) samples were positive and this positivity increased to 26/38 (68%) when we targeted kDNA amplification. Agreement between both techniques (ITS and kDNA PCR) was fair (kappa = 0.219).

CONCLUSIONS

These results indicate that asymptomatic infection is present among the blood donor population of Salvador, a finding that warrants a broader discussion regarding the need to implement specific screening strategies.

Evaluating the accuracy of molecular diagnostic testing for canine visceral leishmaniasis using latent class analysis

Host tissues affected by Leishmania infantum have differing degrees of parasitism. Previously, the use of different biological tissues to detect L. infantum DNA in dogs has provided variable results. The present study was conducted to evaluate the accuracy of molecular diagnostic testing (qPCR) in dogs from an endemic area for canine visceral leishmaniasis (CVL) by determining which tissue type provided the highest rate of parasite DNA detection. Fifty-one symptomatic dogs were tested for CVL using serological, parasitological and molecular methods. Latent class analysis (LCA) was performed for accuracy evaluation of these methods. qPCR detected parasite DNA in 100% of these animals from at least one of the following tissues: splenic and bone marrow aspirates, lymph node and skin fragments, blood and conjunctival swabs. Using latent variable as gold standard, the qPCR achieved a sensitivity of 95.8% (CI 90.4–100) in splenic aspirate; 79.2% (CI 68–90.3) in lymph nodes; 77.3% (CI 64.5–90.1) in skin; 75% (CI 63.1–86.9) in blood; 50% (CI 30–70) in bone marrow; 37.5% (CI 24.2–50.8) in left-eye; and 29.2% (CI 16.7–41.6) in right-eye conjunctival swabs. The accuracy of qPCR using splenic aspirates was further evaluated in a random larger sample (n = 800), collected from dogs during a prevalence study. The specificity achieved by qPCR was 76.7% (CI 73.7–79.6) for splenic aspirates obtained from the greater sample. The sensitivity accomplished by this technique was 95% (CI 93.5–96.5) that was higher than those obtained for the other diagnostic tests and was similar to that observed in the smaller sampling study. This confirms that the splenic aspirate is the most effective type of tissue for detecting L. infantum infection. Additionally, we demonstrated that LCA could be used to generate a suitable gold standard for comparative CVL testing.

Climate and leishmaniasis in French Guiana

To study the link between climatic variables and the incidence of leishmaniasis a study was conducted in Cayenne, French Guiana. Patients infected between January 1994 and December 2010. Meteorological data were studied in relation to the incidence of leishmaniasis using an ARIMA model. In the final model, the infections were negatively correlated with rainfall (with a 2-month lag) and with the number of days with rainfall > 50 mm (lags of 4 and 7 months). The variables that were positively correlated were temperature and the Multivariate El Niño Southern Oscillation Index with lags of 8 and 4 months, respectively. Significantly greater correlations were observed in March for rainfall and in November for the Multivariate El Niño/Southern Oscillation Index. Climate thus seems to be a non-negligible explanatory variable for the fluctuations of leishmaniasis. A decrease in rainfall is linked to increased cases 2 months later. This easily perceptible point could lead to an interesting prevention message.

Molecular diagnosis of canine visceral leishmaniasis: a comparative study of three methods using skin and spleen from dogs with natural Leishmania infantum infection

Polymerase chain reaction (PCR) and its variations represent highly sensitive and specific methods for Leishmania DNA detection and subsequent canine visceral leishmaniasis (CVL) diagnosis. The aim of this work was to compare three different molecular diagnosis techniques (conventional PCR [cPCR], seminested PCR [snPCR], and quantitative PCR [qPCR]) in samples of skin and spleen from 60 seropositive dogs by immunofluorescence antibody test and enzyme-linked immunosorbent assay. Parasitological analysis was conducted by culture of bone marrow aspirate and optical microscopic assessment of ear skin and spleen samples stained with Giemsa, the standard tests for CVL diagnosis. The primers L150/L152 and LINR4/LIN17/LIN19 were used to amplify the conserved region of the Leishmania kDNA minicircle in the cPCR, and snPCR and qPCR were performed using the DNA polymerase gene (DNA pol α) primers from Leishmania infantum. The parasitological analysis revealed parasites in 61.7% of the samples. Sensitivities were 89.2%, 86.5%, and 97.3% in the skin and 81.1%, 94.6%, and 100.0% in spleen samples used for cPCR, snPCR, and qPCR, respectively. We demonstrated that the qPCR method was the best technique to detect L. infantum in both skin and spleen samples. However, we recommend the use of skin due to the high sensitivity and sampling being less invasive.

Proteins of Leishmania (Viannia) shawi confer protection associated with Th1 immune response and memory generation

BACKGROUND

Leishmania (Viannia) shawi parasite was first characterized in 1989. Recently the protective effects of soluble leishmanial antigen (SLA) from L. (V.) shawi promastigotes were demonstrated using BALB/c mice, the susceptibility model for this parasite. In order to identify protective fractions, SLA was fractionated by reverse phase HPLC and five antigenic fractions were obtained.

METHODS

F1 fraction was purified from L. (V.) shawi parasite extract by reverse phase HPLC. BALB/c mice were immunized once a week for two consecutive weeks by subcutaneous routes in the rump, using 25 μg of F1. After 1 and 16 weeks of last immunization, groups were challenged in the footpad with L. (V.) shawi promastigotes. After 2 months, those same mice were sacrificed and parasite burden, cellular and humoral immune responses were evaluated.

RESULTS

The F1 fraction induced a high degree of protection associated with an increase in IFN-γ, a decrease in IL-4, increased cell proliferation and activation of CD8+T lymphocytes. Long-term protection was acquired in F1-immunized mice, associated with increased CD4+ central memory T lymphocytes and activation of both CD4+ and CD8+ T cells. In addition, F1-immunized groups showed an increase in IgG2a levels.

CONCLUSIONS

The inductor capability of antigens to generate memory lymphocytes that can proliferate and secrete beneficial cytokines upon infection could be an important factor in the development of vaccine candidates against American Tegumentary Leishmaniasis.

Qualitative and quantitative polymerase chain reaction (PCR) for detection of Leishmania in spleen samples from naturally infected dogs

Because infected dogs are widely considered to be the main domestic reservoir for Leishmania infantum (syn Leishmania chagasi) parasites in Brazil, the diagnosis of canine visceral leishmaniasis (CVL) must be made both accurately and promptly. The present study attempted to standardize a conventional polymerase chain reaction (cPCR) protocol for the detection of L. infantum DNA in canine spleen samples. Quantitative PCR (qPCR) technique was used to confirm the presence of Leishmania DNA in the canine spleen fragments. A comparison was made between the efficacies of these molecular diagnostic techniques and conventional parasitological and serological methods. cPCR protocols for spleen samples were standardized using primers that amplify a 145 bp fragment, located at the parasite kinetoplast minicircle. The genus specificity of the cPCR protocol was assessed by its inability to amplify the DNA of other common canine pathogens, such as Ehrlichia canis, Babesia canis, Toxoplasma gondii and Trypanosoma cruzi. cPCR protocol sensitivity was tested by assessing the reaction detection limit, determined to be 10 fg of L. infantum reference strain DNA, which corresponds to a range of 0.03-0.1 parasites per fragment. Standardized cPCR protocol was used to detect the presence of Leishmania in 45 dog spleen samples. Our results showed that 40% of the spleen fragment cultures were positive for Leishmania parasites, 58% of the dog serum samples tested positive using ELISA, and parasite DNA was detected in 44% using qPCR, while 47% of the spleen samples using cPCR. Diagnostic methods performance was assessed and revealed a better degree of ascertainment for cPCR when compared to other diagnostic methods. The sensitivity of ELISA was 83.3%, qPCR was 83.3%, and cPCR was 88.9%; PPV for ELISA was 57.7%, qPCR was 75% and cPCR was 76.2%; the Kappa coefficients were found to be 0.40 (fair) for ELISA, 0.64 (substantial) for qPCR and 0.68 (substantial) for cPCR. In both oligosymptomatic and polysymptomatic dogs, cPCR revealed the better performance analysis when compared to other diagnostic methods. The findings presented herein establish cPCR as the most indicated test to detect Leishmania when compared to the other two diagnostic methods evaluated. Despite the fact that the qPCR protocol provides a highly accurate quantification of parasites when targeting the SSU rRNA gene, this technique does not significantly improve the diagnosis of CVL when compared with the performance of the cPCR protocol, which focused on the kinetoplast minicircle.

Flebotomíneos (Diptera, Psychodidae) de área de cerrado no Município de Corumbataí, Centro-Leste do Estado de São Paulo, Brasil

O conhecimento da distribuição e ecologia das espécies de flebotomíneos é fundamental para a vigilância epidemiológica das leishmanioses. A pesquisa e a divulgação do encontro destes insetos colaboram para a determinação do risco de transmissão das mesmas. Realizaram-se capturas de flebotomíneos em fragmento de cerrado strictu sensu em área rural do município de Corumbataí, no período de julho a novembro de 2004. Foram utilizadas duas armadilhas luminosas automáticas do tipo CDC, das 18h às 8h, sendo uma coleta por mês, resultando em 112 horas de exposição. Durante o período de estudo, foi capturado um total de 60 flebotomíneos pertencentes a dez espécies diferentes. A espécie mais abundante e a única presente em todas as capturas foi Pintomyia monticola com um total de 15 (25,0%) espécimes, a segunda foi P. pessoai com 14 (23,3%) e a terceira Brumptomyia guimaraesi com 12 (20,0%) indivíduos coletados. As demais espécies, Psathyromyia aragaoi, B. avellari, B. brumpti, B. cunhai, Pintomyia bianchigalatiae, Evandromyia termitophila e Nyssomyia whitmani somaram 19 (31,2%) exemplares capturados. A presença de P. pessoai e N. whitmani indica risco de transmissão da Leishmaniose Tegumentar Americana na área estudada.

A killed Leishmania vaccine with sand fly saliva extract and saponin adjuvant displays immunogenicity in dogs

A vaccine against canine visceral leishmaniasis (CVL), comprising Leishmania braziliensis promastigote protein, sand fly gland extract (SGE) and saponin adjuvant, was evaluated in dog model, in order to analyse the immunogenicity of the candidate vaccine. The vaccine candidate elicited strong antigenicity in dogs in respect of specific SGE and Leishmania humoral immune response. The major saliva proteins recognized by serum from immunized dogs exhibited molecular weights of 35 and 45 kDa, and were related to the resistance pattern against Leishmania infection. Immunophenotypic analysis revealed increased circulating CD21⁺ B-cells and CD5⁺ T-cells, reflected by higher counts of CD4⁺ and CD8⁺ T-cells. The observed interaction between potential antigen-presenting cells (evaluated as CD14⁺ monocytes) and lymphocyte activation status indicated a relationship between innate and adaptive immune responses. The higher frequency in L. chagasi antigen-specific CD8⁺ T-lymphocytes, and their positive association with intense cell proliferation, in addition to the progressively higher production of serum nitric oxide levels, showed a profile compatible with anti-CVL vaccine potential. Further studies on immunological response after challenge with L. chagasi may provide important information that will lead to a better understanding on vaccine trial and efficacy.

Comparing models for early warning systems of neglected tropical diseases

Background

Early warning systems (EWS) are management tools to predict the occurrence of epidemics of infectious diseases. While climate-based EWS have been developed for malaria, no standard protocol to evaluate and compare EWS has been proposed. Additionally, there are several neglected tropical diseases whose transmission is sensitive to environmental conditions, for which no EWS have been proposed, though they represent a large burden for the affected populations.

Methodology/Principal Findings

In the present paper, an overview of the available linear and non-linear tools to predict seasonal time series of diseases is presented. Also, a general methodology to compare and evaluate models for prediction is presented and illustrated using American cutaneous leishmaniasis, a neglected tropical disease, as an example. The comparison of the different models using the predictive R² for forecasts of “out-of-fit” data (data that has not been used to fit the models) shows that for the several linear and non-linear models tested, the best results were obtained for seasonal autoregressive (SAR) models that incorporate climatic covariates. An additional bootstrapping experiment shows that the relationship of the disease time series with the climatic covariates is strong and consistent for the SAR modeling approach. While the autoregressive part of the model is not significant, the exogenous forcing due to climate is always statistically significant. Prediction accuracy can vary from 50% to over 80% for disease burden at time scales of one year or shorter.

Conclusions/Significance

This study illustrates a protocol for the development of EWS that includes three main steps: (i) the fitting of different models using several methodologies, (ii) the comparison of models based on the predictability of “out-of-fit” data, and (iii) the assessment of the robustness of the relationship between the disease and the variables in the model selected as best with an objective criterion.

Early Warning Systems (EWS) are management tools to predict the occurrence of epidemics. They are based on the dependence of a given infectious disease on environmental variables. Although several neglected tropical diseases are sensitive to the effect of climate, our ability to predict their dynamics has been barely studied. In this paper, we use several models to determine if the relationship between cases and climatic variability is robust—that is, not simply an artifact of model choice. We propose that EWS should be based on results from several models that are to be compared in terms of their ability to predict future number of cases. We use a specific metric for this comparison known as the predictive R², which measures the accuracy of the predictions. For example, an R² of 1 indicates perfect accuracy for predictions that perfectly match observed cases. For cutaneous leishmaniasis, R² values range from 72% to77%, well above predictions using mean seasonal values (64%). We emphasize that predictability should be evaluated with observations that have not been used to fit the model. Finally, we argue that EWS should incorporate climatic variables that are known to have a consistent relationship with the number of observed cases.

Sources and sinks: revisiting the criteria for identifying reservoirs for American cutaneous leishmaniasis

Molecular-based approaches might be misleading for assessing the 'potential importance' of possible reservoirs for parasites unless used in conjunction with population dynamics and ecological studies that provide an understanding of the linkages between the enzootic transmission cycle (in wild animals) and that in domestic animals. Better understanding of ecological constraints on Leishmania transmission is needed to assess fully the passage of the parasite between its sandfly vector and different mammalian host species. We use a straightforward mathematical framework to illustrate that misuse of association patterns, as guidance for implementation of control measures, can in fact increase the endemism of leishmaniasis.

Diagnóstico molecular da taxa de infecção natural de flebotomíneos (Psychodidae, Lutzomyia) por Leishmania sp na Amazônia maranhense

A taxa de infecção natural de três diferentes espécies de flebotomíneos por Leishmania foi estudada usando a técnica de reação em cadeia da polimerase. Primers específicos para Leishmania foram designados para examinar se os pools de flebotomíneos estavam infectadas. Um total de 1.100 fêmeas separadas em pools de 10 indivíduos foram examinados, consistindo de 50 Lutzomyia whitmani, 43 Lutzomyia triacantha e 17 Lutzomyia choti. De todos os pools analisados, 4 de Lutzomyia whitmani estavam positivos, mas nenhum pool das duas espécies restantes estava infectado. Deste modo, uma taxa de infecção de 0,4% foi verificada neste estudo. Esta taxa de infecção associada a estudos anteriores sugere que Lutzomyia whitmani transmite Leishmania aos mamíferos em Buriticupu, Maranhão.

Citometria de fluxo no diagnóstico da leishmaniose visceral canina

Descreve-se a padronização de nova metodologia para detecção de anticorpos antiformas promastigotas fixadas de L. (L.) chagasi, por citometria de fluxo (AAPF-IgG), sua aplicabilidade e desempenho na identificação de casos de leishmaniose visceral canina (LVC). Foram avaliados dois grupos de cães classificados pela reação de imunofluorescência indireta (RIFI), como: não reatores (NR, n=10) e reatores (R, n=50) dos quais foram coletadas amostras de sangue (soro) para realização dos testes laboratoriais. Os resultados relacionados ao estabelecimento, aplicabilidade e desempenho da metodologia AAPF-IgG demonstraram que essa metodologia possibilita a identificação de uma região de reatividade diferencial entre cães NR e R, no soro diluído a 1:2048 e o valor de 20% de parasitos fluorescentes positivos (PPFP) como ponto de corte entre resultados positivos e negativos, mostrando que a AAPF-IgG aplica-se na identificação de casos de LVC, possibilitando distinguir 96% de cães R como positivos e 100% de cães NR como negativos. Esses resultados em conjunto sugerem que a utilização da AAPF-IgG pode ser um novo instrumento para ensaios clínicos de diagnóstico sorológico da LVC.

Climate cycles and forecasts of cutaneous leishmaniasis, a nonstationary vector-borne disease

BACKGROUND

Cutaneous leishmaniasis (CL) is one of the main emergent diseases in the Americas. As in other vector-transmitted diseases, its transmission is sensitive to the physical environment, but no study has addressed the nonstationary nature of such relationships or the interannual patterns of cycling of the disease.

METHODS AND FINDINGS

We studied monthly data, spanning from 1991 to 2001, of CL incidence in Costa Rica using several approaches for nonstationary time series analysis in order to ensure robustness in the description of CL's cycles. Interannual cycles of the disease and the association of these cycles to climate variables were described using frequency and time-frequency techniques for time series analysis. We fitted linear models to the data using climatic predictors, and tested forecasting accuracy for several intervals of time. Forecasts were evaluated using "out of fit" data (i.e., data not used to fit the models). We showed that CL has cycles of approximately 3 y that are coherent with those of temperature and El Niño Southern Oscillation indices (Sea Surface Temperature 4 and Multivariate ENSO Index).

CONCLUSIONS

Linear models using temperature and MEI can predict satisfactorily CL incidence dynamics up to 12 mo ahead, with an accuracy that varies from 72% to 77% depending on prediction time. They clearly outperform simpler models with no climate predictors, a finding that further supports a dynamical link between the disease and climate.

Reproduction of Leishmania (Leishmania ) infantum chagasi in conditioned cell culture growth medium

Leishmanias can be produced by inoculation in conditioned McCoy cell culture growth medium (CGM). Leishmania (Leishmania) infantum chagasi (100 parasites) grown in NNN medium was inoculated in 2.5 mL CGM, kept in plates (24 wells) and its multiplication was observed for five days (120 hours). After day 5, the medium was saturated with the flagellate forms of the parasite (promastigotes). The reproduction of the leishmanias was observed every 24 hours and the number of parasites was calculated by counting the parasites in a drop of 10 µ L and photomicrographied. So the number of Leishmanias was adjusted to 1 mL volume. The advantage of the technique by isolation of Leishmania in CGM demonstrated in this study is its low cost and high efficacy even with a small quantity of parasites (10² promastigotes) used as inoculum. Additionally, isolation of the leishmania can be obtained together with an increase in their density (180 times) as observed by growth kinetics, within a shorter time. These results justify the use of this low-cost technique for the isolation and investigation of the behavior and multiplication of Leishmania both in vertebrates and invertebrates, besides offering means of obtaining antigens, whether whole antigens (leishmanias) or the soluble antigens produced by the parasites which may be useful for the production of new diagnostic kits.

A sensitive flow cytometric methodology for studying the binding of L. chagasi to canine peritoneal macrophages

BACKGROUND

The Leishmania promastigote-macrophage interaction occurs through the association of multiple receptors on the biological membrane surfaces. The success of the parasite infection is dramatically dependent on this early interaction in the vertebrate host, which permits or not the development of the disease. In this study we propose a novel methodology using flow cytometry to study this interaction, and compare it with a previously described "in vitro" binding assay.

METHODS

To study parasite-macrophage interaction, peritoneal macrophages were obtained from 4 dogs and adjusted to 3 x 10(6) cells/mL. Leishmania (Leishmania) chagasi parasites (stationary-phase) were adjusted to 5 x 10(7) cells/mL. The interaction between CFSE-stained Leishmania chagasi and canine peritoneal macrophages was performed in polypropylene tubes to avoid macrophage adhesion. We carried out assays in the presence or absence of normal serum or in the presence of a final concentration of 5% of C5 deficient (serum from AKR/J mice) mouse serum. Then, the number of infected macrophages was counted in an optical microscope, as well as by flow citometry. Macrophages obtained were stained with anti-CR3 (CD11b/CD18) antibodies and analyzed by flow citometry.

RESULTS

Our results have shown that the interaction between Leishmania and macrophages can be measured by flow cytometry using the fluorescent dye CFSE to identify the Leishmania, and measuring simultaneously the expression of an important integrin involved in this interaction: the CD11b/CD18 (CR3 or Mac-1) beta2 integrin.

CONCLUSION

Flow cytometry offers rapid, reliable and sensitive measurements of single cell interactions with Leishmania in unstained or phenotypically defined cell populations following staining with one or more fluorochromes.

Canine visceral leishmaniasis: a histopathological study of lymph nodes

Canine visceral leishmaniasis (CVL) is a zoonosis and a chronic systemic disease of the dog caused by a protozoan of the genus Leishmania. In the New World, the disease is caused by the species Leishmania (Leishmania) chagasi. There are only a few studies on the histopathology of lymph nodes in canine leishmaniasis. In the present paper, we report a histopathological description of lymph nodes considering animals with a defined clinical status and the parasite burden of lymph node tissues. Forty-eight mongrel dogs naturally infected with L. chagasi, were obtained from two endemic areas of Brazil. Cervical, axillary and popliteal lymph nodes were analyzed. The parasite burden, expressed as "Leishman-Donovan units", was variable among the defined types of clinical condition. Asymptomatic dogs can show higher parasitism than oligosymptomatic or symptomatic animals. Grossly, a generalized lymphadenopathy was found, but it was mainly observed in cervical and popliteal nodes. Histologically, the increased number and size of lymphoid follicles, and the marked hypertrophy and hyperplasia of medullary macrophages (cords and sinus) explained the lymphadenopathy. In addition, the clinical status or the tissue parasitism load might not be directly related to the intensity of the lesions.

Changing epidemiology of American cutaneous leishmaniasis (ACL) in Brazil: a disease of the urban-rural interface

American cutaneous leishmaniasis (ACL) was first reported from the south-western region of the state of Rio Grande do Norte in 1987. São Miguel municipality and adjacent areas have accounted for 90% of the American cutaneous leishmaniasis cases in the region since then. A population survey conducted in São Miguel and adjacent areas was undertaken to identify individuals with a history of ACL. The incidence of ACL, distribution by age and gender, clinical characteristics, family clustering, relationship to animals, association with skin test responses, and development of mucosal lesions were determined. Males and females were equally likely to be infected by Leishmania. Thirty-eight percent of the individuals tested were found to be Montenegro skin test positive. No difference in the Montenegro skin test was observed with gender, but the response increased with age. Among the 140 ACL cases treated in a 4-year period in São Miguel, five (3.6%) developed mucosal involvement. Sandflies capable of transmitting Leishmania were captured inside households and in the areas surrounding them. The high density of sandfly species potentially able to transmit Leishmania species and the age distribution of cases of cutaneous leishmaniasis suggest that transmission of the parasite occurred inside or in close proximity to houses.

A follow-up of Beagle dogs intradermally infected with Leishmania chagasi in the presence or absence of sand fly saliva

In this study, we compare the development of infection and/or disease in Beagle dogs intradermally infected with Leishmania chagasi, in the presence or absence of Lutzomyia longipalpis saliva, with those of intravenously infected animals. Spleen samples of all the animals inoculated with parasites had positive polymerase chain reaction tests for Leishmania DNA. Positive spleen cultures for Leishmania were detected earlier (P < or = 0.018) and were more frequent (five out of the five animals) in intravenously infected animals than in the intradermally infected animals, in presence (two out of the six animals) or absence (three out of the five animals) of salivary gland lysate of L. longipalpis. Significant increase in serum antibodies against Leishmania was observed only in the intravenously infected group (P = 0.004). In addition, dogs with infection confirmed by isolation of amastigotes or detection of parasite DNA were, nevertheless, negative for anti-Leishmania antibodies up to 5 months or more after infection. Only animals of the intravenously infected group developed progressive decreases in hematocrit (Pearson r = -0.8076, P = -0.0026) and hemoglobin (Pearson r = -0.8403, P = 0.0012) during the infection period. No significant difference in the course of infection was observed between groups of intradermally infected animals. The data presented herein confirms that the intradermal inoculation of dogs with Leishmania produces an asymptomatic form of infection. It also fails to show an advantage in using L. longipalpis saliva as an infection-enhancing agent in experimental canine leishmaniasis.