High seroprevalence and peripheral spatial distribution of visceral leishmaniasis among domestic dogs in an emerging urban focus in Central Brazil: a cross-sectional study

Global Distribution of Canine Visceral Leishmaniasis and the Role of the Dog in the Epidemiology of the Disease

Visceral leishmaniasis is a disease caused by protozoa of the species Leishmania (Leishmania) infantum (syn = Leishmania chagasi) and Leishmania (Leishmania) donovani, which are transmitted by hematophagous insects of the genera Lutzomyia and Phlebotomus. The domestic dog (Canis familiaris) is considered the main urban reservoir of the parasite due to the high parasite load on its skin, serving as a source of infection for sandfly vectors and, consequently, perpetuating the disease in the urban environment. Some factors are considered important in the perpetuation and spread of canine visceral leishmaniasis (CVL) in urban areas, such as stray dogs, with their errant behavior, and houses that have backyards with trees, shade, and organic materials, creating an attractive environment for sandfly vectors. CVL is found in approximately 50 countries, with the number of infected dogs reaching millions. However, due to the difficulty of controlling and diagnosing the disease, the number of infected animals could be even greater. In the four continents endemic for CVL, there are reports of disease expansion in endemic countries such as Brazil, Italy, Morocco, and Tunisia, as well as in areas where CVL is not endemic, for example, Uruguay. Socio-environmental factors, such as migration, drought, deforestation, and global warming, have been pointed out as reasons for the expansion into areas where it had been absent. Thus, the objective of this review is to address (i) the distribution of CVL in endemic areas, (ii) the role of the dog in the visceral leishmaniasis epidemiology and the factors that influence dog infection and the spread of the disease, and (iii) the challenges faced in the control of CVL.

Intra-urban differences underlying leprosy spatial distribution in central Brazil: geospatial techniques as potential tools for surveillance

This ecological study identified an aggregation of urban neighbourhoods spatial patterns in the cumulative new case detection rate (NCDR) of leprosy in the municipality of Rondonópolis, central Brazil, as well as intra-urban socioeconomic differences underlying this distribution. Scan statistics of all leprosy cases reported in the area from 2011 to 2017 were used to investigate spatial and spatiotemporal clusters of the disease at the neighbourhood level. The associations between the log of the smoothed NCDR and demographic, socioeconomic, and structural characteristics were explored by comparing multivariate models based on ordinary least squares (OLS) regression, spatial lag, spatial error, and geographically weighted regression (GWR). Leprosy cases were observed in 84.1% of the neighbourhoods of Rondonópolis, where 848 new cases of leprosy were reported corresponding to a cumulative NCDR of 57.9 cases/100,000 inhabitants. Spatial and spatiotemporal high-risk clusters were identified in western and northern neighbourhoods, whereas central and southern areas comprised low-risk areas. The GWR model was selected as the most appropriate modelling strategy (adjusted R²: 0.305; AIC: 242.85). By mapping the GWR coefficients, we identified that low literacy rate and low mean monthly nominal income per household were associated with a high NCDR of leprosy, especially in the neighbourhoods located within high-risk areas. In conclusion, leprosy presented a heterogeneous and peripheral spatial distribution at the neighbourhood level, which seems to have been shaped by intra-urban differences related to deprivation and poor living conditions. This information should be considered by decision-makers while implementing surveillance measures aimed at leprosy control.

Epidemiological patterns related to deaths caused by visceral leishmaniasis in the southern Amazon region of Brazil

Background

We analysed the spatial and spatiotemporal patterns of visceral leishmaniasis (VL) mortality at the municipality level in an endemic state in the southern Amazon region of Brazil. Individual-level factors associated with death due to VL were also investigated.

Methods

All VL cases and deaths reported between 2007 and 2018 were included. The global and local bivariate Moran's index assessed the space–time autocorrelation of smoothed triennial VL mortality. Kulldorff's scan statistics investigated spatial and spatiotemporal clusters. A multivariable logistic regression explored sociodemographic, diagnostic and clinical variables associated with death due to VL.

Results

We observed an overall VL mortality and lethality of 0.14 cases/100 000 inhabitants and 11.2%, respectively. A total of 14% of the municipalities registered at least one VL-related death. In the southeastern mesoregion of the state, we detected high-risk spatial (relative risk [RR] 14.14; p<0.001) and spatiotemporal (RR 15.91; p<0.001) clusters for VL mortality. Bivariate Moran's analysis suggested a high space–time autocorrelation of VL mortality. Death by VL was associated with age ≥48 y (odds ratio [OR] 7.2 [95% confidence interval {CI} 3.4 to 15.3]), displacement for notification (OR 3.3 [95% CI 1.5 to 7.2]) and occurrence of oedema (OR 2.8 [95% CI 1.3 to 6.1]) and bleeding (OR 5.8 [95% CI 2.6 to 12.8]).

Conclusions

VL mortality has a heterogeneous spatiotemporal distribution. The death-related factors suggest late diagnosis as an underlying cause of mortality.

Leishmania infantum infection serosurveillance in stray dogs inhabiting the Madrid community: 2007-2018

Background

Leishmaniosis is an endemic zoonotic disease in the Mediterranean basin caused by Leishmania infantum and transmitted by phlebotomine sandflies. While in dogs disease may be severe, leishmaniosis is also a public health concern as was shown in the largest outbreak of human leishmaniosis (HL) in Europe in 2009 occurring in the Madrid region. The aim of the present study was to assess the applicability of the Leishmaniosis Surveillance Program (LeishSP) established in Madrid in 1996 by examining trends in L. infantum seroprevalence and associated epidemiological risk factors based on data for the 2007–2018 period.

Methods

The study population consisted of 3225 stray dogs from 17 animal shelters collaborating with the LeishSP. Seroprevalences were recorded twice annually (April and November) from 2007 to 2018. In each yearly period, a minimum of 100 dogs were tested to detect dogs infected before and after the sandfly risk season in Madrid area. Each dog was subjected to the same protocol of blood sample collection and clinical examination to collect epidemiological data and clinical signs. Anti-Leishmania-specific IgG was determined by IFAT cut-off ≥ 1:100.

Results

Overall seroprevalence was 6.1% (198 positive dogs). Epidemiological data indicate a significantly higher seroprevalence in dogs > 4 years old, purebred dogs (Pit Bull and related breeds), and medium to large size dogs. There were no seroprevalence differences according to sex and/or season (April and November). In addition, no significant differences were observed according to whether dogs lived inside or outside the HL outbreak area. Remarkably, of 198 dogs testing positive for L. infantum, 64.6% had no clinical signs, indicating a high proportion of clinically healthy infected dogs that could be a potential source of infection.

Conclusions

Results indicate a stable seroprevalence of L. infantum infection after 2006 in stray dogs in Madrid but with a recent slightly increasing trend. These observations support the need to continue with the LeishSP implemented by sanitary authorities of the Madrid Community as an early warning strategy for human and animal leishmaniosis and to enable continued assessment of the epidemiological role of dogs with subclinical infection in this important zoonotic disease.

Graphical Abstract

Passive case detection for canine visceral leishmaniasis control in urban Brazil: Determinants of population uptake

BACKGROUND

In Brazil, the transmission of Leishmania infantum in urban settings is closely related to infection among dogs, with occasional transmission to humans. Serological screening of dogs for Leishmania spp. infection on requests of their owners (passive case detection) represents a frequent, but little studied, practice within the scope of Brazilian public health. This study identified factors associated with canine visceral leishmaniasis (CVL) diagnosis-seeking behavior of dog owners in Rondonópolis (236,000 inhabitants), a municipality in Central-Western Brazil where VL is endemic. Also, we evaluated the profile of dog owners and their animals screened on free demand.

METHODOLOGY/PRINCIPAL FINDINGS

Using mixed effects negative binomial regression, we modelled the number of dogs screened for Leishmania infection on free demand per neighborhood from 2011 to 2016 as a function of time-dependent predictors (current or recent canine seropositivity and human VL incidence), distance to the screening site, and demographic variables. We assessed potential delays in the effect of time-dependent predictors on the outcome. Among 12,536 dogs screened for Leishmania infection, 64.2% were tested during serosurveys and 35.8% were tested on free demand. Of these, 63.9% were positive. Uptake of screening under free demand was strongly associated with higher levels of canine seropositivity in the neighborhood (current or recent) and decreasing distance to the screening site. A subsample of dog owners (n = 93) who sought CVL screening between 2016 and 2017 were interviewed in more detail. Owners with better socioeconomic status and dogs with apparent CVL clinical manifestations prevailed among them.

CONCLUSIONS/SIGNIFICANCE

To support timely CVL management, passive case detection along with awareness activities aimed at dog owners should be encouraged in endemic areas. Screening sites should be prioritized in accessible zones, as well as in socio-economically disadvantage areas. In parallel, CVL active case detection should be continued as a surveillance tool to guide control actions.

Epidemiology of canine visceral leishmaniasis in a vulnerable region in Brazil

Visceral leishmaniasis (VL) is a neglected and endemic zoonosis that occurs throughout Brazil; nevertheless, few studies have focused on the early detection of the disease. The municipality of Ourinhos is a non-receptive, silent and vulnerable area for VL, where the seroprevalence of this disease has so far not been investigated. The present study aimed to determine the seroprevalence of canine VL in Ourinhos-SP, and to identify the presence of risk factors. Blood samples were obtained from 604 dogs during a rabies vaccination campaign together with application of a socioeconomic questionnaire, environmental and animal characteristics and tutor's knowledge about the disease. The samples were subjected to indirect ELISA and new samples were collected from reactive and suspect animals, including whole blood and lymph node aspiration evaluated by parasitological method, complete blood count and PCR. No animal was diagnosed as positive based on the combination of direct and indirect tests and the tutors' answers indicated little knowledge about leishmaniasis, being often confused with other diseases transmitted by arthropods; hence, according to the proposed methods, the presence of canine leishmaniasis in the city of Ourinhos was not confirmed and health education campaigns about the disease should be carried out.

Human visceral leishmaniasis in Central-Western Brazil: Spatial patterns and its correlation with socioeconomic aspects, environmental indices and canine infection

In this ecological study, we investigated spatial patterns of human visceral leishmaniasis (VL) incidence, its correlation with socioeconomic aspects, environmental indices (obtained through remote sensing) and canine VL during 2011-2016 in the municipality of Rondonópolis, a relevant endemic area for VL in Central-Western Brazil. Human VL cases were georeferenced and point patterns were analyzed by univariate Ripley's K function and Kernel density estimation (KDE). Poisson-based scan statistics were used to investigate spatial and spatiotemporal clusters of human VL incidence at the neighborhood level. Socioeconomic and environmental characteristics were compared between neighborhoods within and outside spatial human VL clusters. Also, we assessed the correlation between smoothed human VL incidence and canine VL seropositivity rates within and between neighborhoods. Human VL cases were clustered up to 2000 m; four hotspots were identified by KDE in peripheral areas. Spatial and spatiotemporal low-risk clusters for human VL were identified in central and southern areas. Neighborhoods within spatial low-risk cluster presented higher mean income, literacy rate, sanitary sewage service coverage and lower altitude, compared to the rest of the municipality. A positive correlation was found between the occurrence of human and canine VL. On the northern outskirts, high human VL incidence was spatially correlated with high canine VL seropositivity in surrounding neighborhoods. In conclusion, human VL demonstrated a heterogeneous, aggregated and peripheral spatial pattern. This distribution was correlated with intra-urban socioeconomic differences and canine VL seropositivity at the neighborhood level.

Impact of the dog population and household environment for the maintenance of natural foci of Leishmania infantum transmission to human and animal hosts in endemic areas for visceral leishmaniasis in Sao Paulo state, Brazil

When it comes to visceral leishmaniasis (VL) in Brazil, one of the main targets of public health policies of surveillance is the control of domestic canine reservoirs of Leishmania infantum. This paper aims to evaluate the effect of the dog population and household environment for the maintenance of natural foci in the transmission to human and animal hosts in an endemic city for VL, Bauru, in Brazil. We collected 6,578 blood samples of dogs living in 3,916 households from Nov.2019 to Mar.2020 and applied geospatial models to predict the disease risk based on the canine population. We used Kernel density estimation, cluster analysis, geostatistics, and Generalized Additive Models (GAM). To validate our models, we used cross-validation and created a receiver operating characteristic (ROC) curve. We found an overall canine VL (CVL) seroprevalence of 5.6% for the sampled dogs, while for the households, the positivity rate was 8.7%. Odds ratios (OR) for CVL increased progressively according to the number of canines for >2 dogs (OR 2.70); households that already had CVL in the past increased the chances for CVL currently (OR 2.73); and the cases of CVL increase the chances for human VL cases (OR 1.16). Our models were statistically significant and demonstrated a spatial association between canine and human disease cases, mainly in VL foci that remain endemic. Although the Kernel density ratio map had the best performance (AUC = 82), all the models showed high risk in the city's northwest area. Canine population dynamics must be considered in public policies, and geospatial methods may help target priority areas and planning VL surveillance in low and middle-income countries.

Basic knowledge about visceral leishmaniasis before and after educational intervention among primary health care professionals in Midwestern Brazil

Health education and training of primary health care (PHC) professionals are highly recommended to reduce the occurrence and lethality of visceral leishmaniasis (VL). This study assessed the impact of an educational intervention on the basic knowledge about visceral leishmaniasis (VL) among PHC professionals from the Brazilian municipality of Rondonopolis, an important endemic area for VL. Responses provided by physicians, nurses, nursing technicians and community health agents from 12 PHC facilities were recorded through the application of self-completed and semi-structured questionnaires before (n=92) and after (n=64) an in-person health training course covering various aspects of VL. Closed- and open-ended responses were compared by the chi-square test and analyses of word clouds, respectively. The proportion of professionals aware of the correct etiological agent (p<0.001) and transmission route (p<0.001) of VL increased post-intervention. In addition, they increased their ability to recognize fever (p<0.001), weakness (p<0.001), weight loss (p<0.001), pallor (p<0.001) and abdominal distention (p=0.013) as clinical manifestations of human VL, and weakness (p<0.001), alopecia (p<0.001) and weight loss (p=0.019) as signs of canine VL. Analyses of word clouds suggested that the participants became more aware of the role of dogs in VL transmission and the role of environmental management in the prevention of VL. In conclusion, the intervention positively impacted the baseline knowledge concerning VL among the professionals. This can support the planning of educational activities for the PHC team regarding early case detection, prevention and control of VL in endemic areas.

Are backyard characteristics relevant factors for the occurrence of human visceral leishmaniasis in Central-Western Brazil?

BACKGROUND

This retrospective case-control study aimed to investigate the factors associated with the occurrence of human visceral leishmaniasis (VL) in the municipality of Rondonópolis, which is a highly endemic area for VL in Central-Western Brazil.

METHODS

All VL cases reported in Rondonópolis from 2011 to 2016 were included. For each case, two neighborhood- and age-matched controls with the absence of past and present history of VL and negative rk39-based immunochromatographic test, were recruited. Data were retrospectively collected through interviews that assessed socioeconomic aspects, housing features, backyard characteristics, presence of animals and daily habits. A multivariate conditional logistic regression analysis was used to identify factors associated with human VL.

RESULTS

During the study period, 81 VL cases were reported in Rondonópolis, of which 37 (45.7%) were included in this study. Seventy controls were also included. The variables associated with VL occurrence were the outdoor location of a bathroom and/or kitchen separated from the rest of the house (OR 7.8; 95% CI 2.1 to 29.5), the presence of a vegetable garden (OR 5.3; 95% CI 1.3 to 21.2) and the presence of decaying fruits (OR 10.7; 95% CI 2.0 to 52.1) in the backyard.

CONCLUSIONS

Our findings suggest an association between backyard characteristics and VL. This may be useful in guiding preventive and control measures against zoonotic VL worldwide.

Spatial analysis of canine leishmaniasis in an area of transmission of the semi-arid region of the State of Paraíba, Brazil

Visceral leishmaniasis is a widely distributed zoonosis and canine infection is an important indicator of risk for the occurrence of the disease in humans. The goal of this analysis was to study the spatial clustering of canine leishmaniasis (CL) in the municipality of Santa Luzia, state of Paraíba. For this, 749 samples of canine plasma were tested using three serological tests. The dog was considered positive if it reacted in two serological tests. The location of the residences was performed with a Global Positioning System receiver (GPS Garmin® eTrex 30), and used to perform georeferencing and spatial analysis. The prevalence of CL was 15.49% and it was observed that most cases of the urban area were concentrated in the Frei Damião neighborhood, on the outskirts of the city, where a high-risk cluster for the occurrence of the disease was formed (p = 0.02; RR = 2.48). No statistically significant cluster was observed in rural areas. CL is widely distributed in the municipality of Santa Luzia in a heterogeneous manner and with a tendency to urbanization. The areas identified with high prevalence and highest risk should be prioritized to maximize the efficiency of the Visceral Leishmaniasis Surveillance and Control Program and minimize the chance of new canine and human cases.

Visceral leishmaniasis in Saudi Arabia: From hundreds of cases to zero

The kingdom of Saudi Arabia (KSA) has succeeded in bringing the reported numbers of Visceral leishmaniasis (VL) cases from hundreds during the 1980s and 1990s to zero case in 2019. The endemicity of VL has been confined mainly to the Southwest regions, namely Jazan and Aseer regions. Leishmania donovani species have been identified as the causative species of VL, while L. infantum have been isolated only from dogs in the endemic areas. Many species of sand flies were caught in Southwest, but P. orientalis is the probable transmitter of the disease. The black rat (Rattus ratus) was found to be contributing to maintenance of the parasite life cycle. VL is primarily a disease of children, and 80% of cases were Saudi's, while cases from Yeminis nationality represent the majority of non- Saudi patients. The common clinical presentation consist of chronic fever, abdominal distention, weight loss, anemia and hepatosplenomegaly. Laboratory findings include: anemia, leukopenia, thrombocytopenia, hypoalbuminemia, hyperproteinaemia and hypergammaglobulinemia, low serum iron, and abnormal liver enzymes. Occurrence of jaundice has been identified as a bad prognostic sign. Diagnosis relying on direct smears from bone marrow aspirates was the commonest tool used, and also is advocated by the National Leishmaniasis Control Program (NLCP). Sodium stibogluconate (SSG) is the main drug used to treat VL cases, while Ambisome is preserved for complicated cases. Chemical control of sand flies using indoor residual spraying (IRS) with synthetic pyrethroids has been the most effective measure applied to prevent vector-human contact and disease transmission. The geographical overlap of VL and Malaria has facilitated the adoption and implementation of integrated vector control strategies. After reaching a zero case in 2019, the Ministry of Health (MoH) has a new commitment and facing a great challenge which are maintenance of current situation and elimination of VL. Through the support of stakeholders, encouragement of community participation, preparedness and readiness of leishmaniasis personnel, the new mission of the NLCP now is elimination of the scourge of VL from the country.

First Report of an Urban Case of Canine Visceral Leishmaniasis in the Municipality of Cali, Colombia

American visceral leishmaniasis (VL) is a vector-borne disease caused by Leishmania infantum (syn. chagasi) and transmitted by Lutzomyia longipalpis and Lutzomyia evansi phlebotomine sand flies. Dogs not only are the main host reservoirs of the parasite but also suffer the disease; therefore, canine VL (CVL) has assumed an important role in public health. In Colombia, human and CVL are restricted to two transmission foci: one in the north region (Caribbean coast) and other in the central south region (middle Magdalena River Valley). We present a CVL case involving a 2-year-old male dog with a history of lack of appetite, general weakness, and progressive loss of weight. A diagnosis of CVL was obtained using the direct parasitological examination in spleen and bone marrow samples stained with Giemsa and RT-qPCR. The infecting Leishmania species was identified as L. infantum by PCR-restriction fragment length polymorphism amplifying the Hsp70 gene from bone marrow and spleen samples and confirming by sequencing. The patient responded favorably to treatment with intramuscular meglumine antimoniate at a dose of 100 mg/kg daily for 8 weeks and oral allopurinol at a dose of 10 mg/kg every 12 hours until new indication. This is the first report of urban CVL in the city of Cali, Colombia, highlighting the need for surveillance and control programs in the municipalities of the department of Valle del Cauca, a region where VL has not been informed before. The findings also indicate the need to reinforce the surveillance programs in other rural and urban regions of the country where favorable eco-epidemiological conditions exist.

In vitro and in vivo immunomodulatory properties of octyl-β-D-galactofuranoside during Leishmania donovani infection

BACKGROUND

The chemotherapeutic arsenal available to treat visceral leishmaniasis is currently limited, in view of many drawbacks such as high cost, toxicity or emerging resistance. New therapeutic strategies are particularly needed to improve the management and the outcome in immunosuppressed patients. The combination of an immunomodulatory drug to a conventional anti-Leishmania treatment is an emerging concept to reverse the immune bias from Th2 to Th1 response to boost healing and prevent relapses.

METHODS

Here, immunostimulating and leishmanicidal properties of octyl-β-D-galactofuranose (Galf) were assessed in human monocyte-derived macrophages (HM) and in a murine model, after challenge with Leishmania donovani promastigotes. We recorded parasite loads and expression of various cytokines and immune effectors in HM and mouse organs (liver, spleen, bone marrow), following treatment with free (Galf) and liposomal (L-Galf) formulations.

RESULTS

Both treatments significantly reduced parasite proliferation in HM, as well as liver parasite burden in vivo (Galf, P < 0.05). Consistent with in vitro results, we showed that Galf- and L-Galf-treated mice displayed an enhanced Th1 immune response, particularly in the spleen where pro-inflammatory cytokines TNF-α, IL-1β and IL-12 were significantly overexpressed compared to control group. The hepatic recruitment of myeloid cells was also favored by L-Galf treatment as evidenced by the five-fold increase of myeloperoxidase (MPO) induction, which was associated with a higher number of MPO-positive cells within granulomas. By contrast, the systemic level of various cytokines such as IL-1β, IL-6, IL-17A or IL-27 was drastically reduced at the end of treatment.

CONCLUSIONS

Overall, these results suggest that Galf could be tested as an adjuvant in combination with current anti-parasitic drugs, to restore an efficient immune response against infection in a model of immunosuppressed mice.

Where, when, and how the diagnosis of human visceral leishmaniasis is defined: answers from the Brazilian control program

BACKGROUND

Timely diagnosis is recommended by the Brazilian Visceral Leishmaniasis (VL) Surveillance and Control Program to reduce case fatality. Attempts at assessing this topic in Brazil are scarce.

OBJECTIVE

This study aimed to describe where, when, and how the diagnosis of VL has been performed in a Brazilian endemic setting.

METHODS

Data of all autochthonous cases confirmed between 2011 and 2016 (N = 81) were recorded. The care-seeking itinerary until the confirmation of VL diagnosis was assessed among 57 patients.

FINDINGS

The majority of VL cases (79.1%) were reported by referral hospitals. The patients mainly sought primary health care centres at the onset of symptoms. However, they had to visit seven health services on average to achieve a confirmed diagnosis. The time from the onset of symptoms to the diagnosis of VL (T_D) ranged from 1-212 (median, 25) days. The T_D was longer among adult patients. There was a direct correlation between the patient’s age and T_D (r = 0.22; p = 0.047) and a higher occurrence of deaths due to the disease among older patients (p = 0.002). Almost all the patients (98.9%) underwent laboratory investigation, and the VL diagnosis was mainly confirmed based on clinical-laboratory criteria (92.6%). Positive results for the indirect fluorescence antibody test (22.7%) and parasitological examination plus rk39-based immunochromatographic tests (21.3%) were commonly employed.

MAIN CONCLUSIONS

VL diagnosis was predominantly conducted in hospitals with a long T_D and wide application of serology. These findings may support measures focused on early diagnosis, including a greater involvement of the primary health care system.

High levels of serum glycans monovalent IgG immune complexes detected by dissociative ELISA in experimental visceral leishmaniasis

Visceral leishmaniasis (VL) is epidemic in Brazil with an increasing incidence of human cases and canine reservoirs, with host hypergammaglobulinemia. Conventional enzyme-linked immunosorbent assay (cELISA) based on several parasitic antigens is the main method for diagnosis and indication of treatment. Dissociative ELISA (dELISA) uses acidic treatment to free immunoglobulin G (IgG) from immune complexes, and its use revealed a significant positive fraction of suspected cases with negative serology. Looking for small molecules or haptens that block IgG antibodies, we purified by molecular exclusion chromatography, 1000-3000 MW molecules from promastigote soluble extract, mostly oligosaccharides comprising 6-13 sugar residues using MALDI-TOF analysis. Glycan-BSA complex (GBC) was constructed by conjugating promastigote glycans to BSA molecules, allowing their use in the solid support in cELISA or dELISA. Sera from experimentally infected hamsters showed higher levels of blocked monomeric IgG during infection, mostly against GBC, which was also present in lower concentrations in the promastigote soluble extract dELISA. Those data show that most of the specific monomeric IgG in serum are blocked by haptens composed by glycans produced by the parasite, better detected in the high dilution of sera in the dELISA assays. dELISA is a useful technique for detecting blocked monomeric antibodies that could have difficult clearance from blood, which could result in hypergammaglobulinemia.

Twice upon a time: The progression of canine visceral leishmaniasis in an Argentinean city

Canine Visceral Leishmaniasis (CVL) prevalence, spatial distribution and associated factors were assessed in four locations in Iguazú department in 2014 and in Puerto Iguazú city again in 2018. The city areas were divided into a grid of 400x400m cells. All cells were sampled in 2014 and a random subsampling was developed in 2018. In each cell, five dogs clustered in a 'critical scenario' (prone to have vectors) were sampled. A rapid immunochromatographic dipstick was used to detect antibodies against Leishmania infantum, confirming by lymph node smears observation and PCR. For Puerto Iguazú, Generalized Linear Models (GLMs) were constructed considering environmental, dog and clinical variables. Pearson's Chi square and Fisher's exact tests were employed to evaluate the association between CVL, dog clinical signs and infestation with other parasites. Cartographic outputs were made and Moran's I indices were calculated as spatial autocorrelation indicators. CVL prevalence rates were 26.18% in 2014 and 17.50% in 2018. No associations were established in environmental models, but dog age and repellent use were significant when running 2014 dog models. Clinical models showed significant associations between seropositive dogs and ophthalmological, dermal signs and onychogryphosis in 2014. In 2018, only adenomegaly was associated. The results of global Moran´s I were not significant but regarding local analysis, six sites in 2014 and one in 2018 presented autocorrelation with neighboring sites. The decrease in CVL prevalence may be associated to transmission stabilization, which could explain the lack of associations with dog-related variables. Further, spatial distribution of CVL is a poor evidence for design of transmission control measures but could be important in case of intensive parasite circulation or when the first autochthonous cases appear. For control success, sensitivity of diagnostic methods, political will and adequate material resources remain critical. Modeling of multiple variables will be required to identify factors that drive disease stabilization/destabilization.

Novos adjuvantes vacinais: importante ferramenta para imunoterapia da leishmaniose visceral

Atualmente, muitas das vacinas em desenvolvimento são aquelas compostas de proteínas antigênicas individuais de parasitas ou uma combinação de vários antígenos individuais que são produzidos como produtos recombinantes obtidos por técnicas de biologia molecular. Dentre elas a Leish-111f e sua variação Leish-110f tem ganhado destaque na proteção contra a LV e LC e alcançaram estudos de fase II em seres humanos. A eficácia de uma vacina é otimizada pela adição de adjuvantes imunológicos. No entanto, embora os adjuvantes tenham sido usados por mais de um século, até o momento, apenas alguns adjuvantes são aprovados para o uso em humanos, a maioria destinada a melhorar a eficácia da vacina e a produção de anticorpos protetores específicos do antígeno. Os mecanismos de ação dos adjuvantes imunológicos são diversos, dependendo da sua natureza química e molecular sendo capazes de ativar células imunes especificas que conduzem a respostas imunes inatas e adaptativas melhoradas. Embora o mecanismo de ação molecular detalhado de muitos adjuvantes ainda seja desconhecido, a descoberta de receptores Toll-like (TLRs) forneceu informações críticas sobre o efeito imunoestimulador de numerosos componentes bacterianos que envolvem interação com receptores TLRs, mostrando que estes ligantes melhoram tanto a qualidade como a quantidade de respostas imunes adaptativas do hospedeiro quando utilizadas em formulações de vacinais direcionadas para doenças. O potencial desses adjuvantes de TLR em melhorar o design e os resultados de várias vacinas está em constante evolução, à medida que novos agonistas são descobertos e testados em modelos experimentais e estudos clínicos de vacinação. Nesta revisão, é apresentado um resumo do progresso recente no desenvolvimento de proteínas recombinantes de segunda geração e adjuvantes de TLR, sendo o foco principal nos TLR4 e suas melhorias.

Factors associated with Leishmania spp. infection in domestic dogs from an emerging area of high endemicity for visceral leishmaniasis in Central-Western Brazil

The factors associated with Leishmania spp. infection in dogs are still poorly understood. This study aimed to identify such factors among domestic dogs from the Brazilian municipality of Rondonópolis, which recently emerged as an endemic area with intense transmission of human visceral leishmaniasis (VL). It was a household-based cross-sectional study conducted between 2016 and 2017. Interviews were conducted with 405 dog owners considering their socioeconomic characteristics, and environmental aspects of the household and its adjacent areas. In addition, 600 dogs were evaluated regarding physical characteristics, behavior, and care provided by the owner. Seropositive animals were those that showed reactivity in a rapid immunochromatographic test and enzyme-linked immunosorbent assay, which are currently recommended for canine visceral leishmaniasis (CVL) diagnosis in Brazil. A multivariable logistic regression analysis was employed to determine the associated factors. Low social class [OR = 2.0; _95%CI = (1.2-3.2)], presence of acerola tree (Malpighia emarginata) in the yard [OR = 2.2; _95%CI = (1.2-4.1)], presence of more than one dog in the household [OR = 2.0; _95%CI = (1.3-3.3)], horse and/or cattle breeding [OR = 12.0; _95%CI = (1.9-73.6)], existence of houses with yard adjacent to the home [OR = 4.0; _95%CI = (1.3-12.2)], presence of apparent signs consistent with CVL [OR = 10.6; _95%CI = (5.8-19.4)], dog staying mostly in the yard during the day [(OR = 4.8; _95%CI = (1.1-21.4)], and lack of cleaning of the dog's shelter [(OR = 1.9; _95%CI = (1.1-3.2)] were identified as the factors associated with Leishmania spp. infection. These results support the importance of socioeconomic and environmental aspects in the occurrence of Leishmania spp. infection. In addition, they may be useful in guiding control strategies in areas where zoonotic VL is endemic.

First autochthonous case of canine visceral leishmaniasis in Rondônia, Brazil, a region with no history of visceral leishmaniasis

This report describes the first autochthonous case of canine visceral leishmaniasis in Rondônia, northern Brazil. A canine resident of the municipality of Cacoal, with clinical signs and symptoms of visceral leishmaniasis, was treated by a veterinarian. Samples were analyzed by a reference laboratory. Dual-path platform (DPP) assay, indirect immunofluorescence technique (IIT), enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), isolation in a culture medium, and direct parasitological analysis were performed. DPP assay, IIT, and ELISA revealed positive results for Leishmania; PCR identified the species as Leishmania infantum. Based on the clinical presentation and test results, canine visceral leishmaniasis was diagnosed.

Estimating the efficacy of community-wide use of systemic insecticides in dogs to control zoonotic visceral leishmaniasis: A modelling study in a Brazilian scenario

Systemic insecticides in dogs have been suggested as a public health intervention to prevent human cases of Zoonotic Visceral Leishmaniasis (ZVL). But, currently there are no systemic insecticides for dogs registered against zoo-anthropophilic pool blood feeding phlebotomine flies. We predict the impact of community-wide use of systemic insecticide in dog populations as a public health measure to control transmission of Leishmania infantum to humans using a mathematical model. We developed a Susceptible-Exposed-Infected (SEI) compartmental model to describe L. infantum transmission dynamics in dogs, with a vectorial capacity term to represent transmission between L. infantum-hosting dogs via phlebotomine flies. For Infected (I) dogs two levels of infectiousness were modelled, high infectiousness and low infectiousness. Human incidence was estimated through its relationship to infection in the dog population. We evaluated outcomes from a wide range of scenarios comprising different combinations of initial insecticide efficacy, duration of insecticide efficacy over time, and proportion of the dog population treated (60%, 70% & 80%). The same reduction in human infection incidence can be achieved via different combinations of insecticide efficacy, duration and dog coverage. For example, a systemic insecticide with an initial efficacy of 80% and 6 months above 65% efficacy would require treating at least 70% of the dogs to reduce the human infection incidence by 50%. Sensitivity analysis showed that the model outcome was most sensitive to baseline values of phlebotomine fly daily survival rate and insecticide coverage. Community-wide use of systemic insecticides applied to the “L. infantum canine reservoir” can significantly reduce human incidence of L. infantum infection. The results of this mathematical model can help defining the insecticide target product profile and how the insecticide should be applied to maximise effectiveness.

Zoonotic visceral leishmaniasis (ZVL) is a potentially deadly disease in humans caused by Leishmania infantum. This leishmania species can be delivered by pool blood feeding zoo-anthropophilic phlebotomine flies to several mammals, the dog population being recognized as the main reservoir. Transmission from infected dogs to humans is through the bite of female phlebotomine sand flies. The disease is endemic in several countries and Brazil has a high prevalence of cases with over 3000 ZVL cases reported per year. The main, inefficient and highly controversial, control measure in Brazil has been culling sero-positive dogs. The community-wide use of systemic insecticides in dogs could be an alternative to control L. infantum transmission from phlebotomine flies to humans. The rationale is that phlebotomine flies which sampled their blood meals from dogs treated with systemic insecticides would die reducing the risk of L. infantum transmission. To reduce the number of ZVL cases, a large proportion of dogs in the community should be treated and the systemic insecticide used should be effective in killing phlebotomine flies acting as vectors of L. infantum parasites for a significant amount of time. We used a mathematical model mimicking L. infantum transmission to show that this novel vector control strategy could be effective. We identified the combination of different key parameters (e.g. insecticide efficacy, duration and proportion of dogs treated) that could lead to a significant reduction of the risk of L. infantum infection in humans.