Evaluation of a novel chromatographic immunoassay based on Dual-Path Platform technology (DPP® CVL rapid test) for the serodiagnosis of canine visceral leishmaniasis

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.

Finding Priority Areas in the Evaluation of Strategies for the Prevention of Leishmaniasis in an Endemic Municipality of Brazil

Visceral leishmaniasis is a zoonotic disease that affects humans and dogs. The infection is endemic in the municipality of Araçatuba, São Paulo, Brazil. Given the role of dogs in the epidemiology of leishmaniasis, strategies to enhance surveillance and reduce transmission are focused on dogs. In this study, we retrospectively analyzed records of canine visceral leishmaniasis from 2013 to 2022. According to this database, the prevalence of dogs testing positive for leishmaniasis fluctuated, with an average of 65.04% (6590/10,133). Cases were clustered in 10 statistically significant areas. Environmental analyses identified a significant geographical association between animals testing positive and higher vegetation density rates compared with animals testing negative. The period from sample collection to diagnosis and euthanasia, as recommended by the Brazilian Ministry, correlated with disease prevalence and decreased over time. These findings serve to implement different action plans against leishmaniasis for each geographic region and to understand the impact and efforts of strategies in an endemic area.

Comparative Study of Colorimetric In Situ Hybridization and Quantitative Real-Time Polymerase Chain Reaction for Diagnosis of Infection by Leishmania infantum in Dogs in Formalin-Fixed and Paraffin-Embedded Skin

The zoonotic visceral leishmaniasis is caused by the protozoan Leishmania infantum and dogs are reservoirs for this parasite. For the diagnosis of Leishmania at the species level in dogs in formalin-fixed, paraffin-embedded skin (FFPES) samples, colorimetric in situ hybridization (CISH) and quantitative real-time polymerase chain reaction (qPCR) are options, but their sensitivities are not well established. Therefore, the aim of this study was to determine the sensitivity of these two techniques in FFPES for the diagnosis of the L. infantum infection in dogs using culture as the reference standard. The FFPES of 48 dogs with cutaneous infection by L. infantum confirmed by culture and by multilocus enzyme electrophoresis were examined by CISH and qPCR using specific probes for L. infantum. The sensitivities of qPCR, CISH and their combination were, respectively, 77.0%, 58.0% and 83.3%. The sensitivities of qPCR in dogs with and without clinical signs were, respectively, 74.2% and 82.4%. The sensitivities of CISH in dogs with and without clinical signs were, respectively, 61.3% and 52.9%. The CISH and qPCR showed satisfactory sensitivities for the diagnosis of L. infantum in the FFPES of dogs, even in dogs without clinical signs, and their combination increases the sensitivity for this diagnosis.

Diagnostic Potential for the Detection of Canine Visceral Leishmaniasis of an ELISA Assay Based on the Q5 Recombinant Protein: A Large-Scale and Comparative Evaluation Using Canine Sera with a Positive Diagnosis from the Dual-Path-Platform (DPP) Test

Dogs are considered the major domestic reservoir for human visceral leishmaniasis, a serious disease caused by the Leishmania infantum parasite. Diagnosis of canine visceral leishmaniasis (CVL) is critical for disease control, with several methods currently available. Among the serological tests, the DPP rapid test and the EIE-LVC, more commonly used in Brazil, are associated with variable sensitivity and specificity. Research with novel recombinant proteins such as the ELISA with the recombinant chimeric protein Q5 may therefore improve the CVL diagnosis. This study aimed to evaluate the true diagnostic potential of Q5 in an ELISA assay using a large number of CVL-suspected sera (406) with a previous positive diagnosis based on the rapid DPP test. Sera from the DPP-positive dogs, also assessed with the EIE-LVC test, were compared with sera from healthy dogs (n = 46) and used for ELISA tests using the recombinant Q5. The resulting data as well as the correlation with the clinical signs and the environmental characteristics of the animals were analyzed using Medal and GraphPad Prism 8.0. Overall, similar levels of lower sensitivity (67-68%) were seen for both the commercial EIE-LVC test and the Q5 ELISA when all assessed sera were considered, but a much greater sensitivity (92%) was seen for those samples from symptomatic dogs only. In contrast, many negative results were observed for the DPP-positive sera from asymptomatic dogs or those with no clinical information available. A selection of those sera were tested yet again in new ELISA assays using a second batch of the recombinant Q5, purified under milder denaturing conditions, as well as using another recombinant protein (Lci13). The results reveal a higher-than-expected incidence of likely false-positive results for DPP, reinforcing the need for other recombinant proteins, such as the chimeric Q5, to be investigated as possible alternatives to the currently used CVL diagnostic methods.

Immunoproteomics approach for the discovery of antigens applied to the diagnosis of canine visceral leishmaniasis

In the present study, an immunoproteomic approach using Leishmania infantum parasites isolated from naturally infected dogs from an endemic region of the disease, was carried out to identify new antigens to be used in the diagnosis of canine visceral leishmaniasis (CVL). Protein extracts, obtained from parasites isolated from asymptomatic (CanLA) and symptomatic (CanLS) dogs, were used to perform the two-dimensional gels. Western Blotting assays were carried out by employing a pool of sera from dogs with visceral leishmaniasis (CanLA or CanLS), healthy dogs from an endemic area, or dogs with similar diseases associated with cross-reactions (babesiosis and ehrlichiosis). With these results, it was possible to exclude the spots that showed a cross-reactivity of the sera from groups of healthy dogs, and those with babesiosis or ehrlichiosis. Taken together, 20 proteins were identified, 15 of which have already been described in the literature and 5 of which are hypothetical. An immunogenomic screen strategy was applied to identify conserved linear B-cell epitopes in the identified hypothetical proteins. Two peptides were synthesized and tested in ELISA experiments as a proof of concept for the validation of our immunoproteomics findings. The results demonstrated that the antigens presented sensitivity and specificity values ranging from 81.93% to 97.59% and 78.14 to 85.12%, respectively. As a comparative antigen, a preparation of a Leishmania extract showed sensitivity and specificity values of 75.90% and 74.88%, respectively. The present study was able to identify proteins capable of being used for the serodiagnosis of canine visceral leishmaniasis.

rMELEISH: A Novel Recombinant Multiepitope-Based Protein Applied to the Serodiagnosis of Both Canine and Human Visceral Leishmaniasis

BACKGROUND

visceral leishmaniasis (VL) is a critical public health problem in over ninety countries. The control measures adopted in Brazil have been insufficient when it comes to preventing the spread of this overlooked disease. In this context, a precise diagnosis of VL in dogs and humans could help to reduce the number of cases of this disease. Distinct studies for the diagnosis of VL have used single recombinant proteins in serological assays; however, the results have been variable, mainly in relation to the sensitivity of the antigens. In this context, the development of multiepitope-based proteins could be relevant to solving such problem.

METHODS

a chimeric protein (rMELEISH) was constructed based on amino acid sequences from kinesin 39 (k39), alpha-tubulin, and heat-shock proteins HSP70 and HSP 83.1, and tested in enzyme-linked immunosorbent (ELISA) for the detection of L. infantum infection using canine (n = 140) and human (n = 145) sera samples.

RESULTS

in the trials, rMELEISH was able to discriminate between VL cases and cross-reactive diseases and healthy samples, with sensitivity and specificity values of 100%, as compared to the use of a soluble Leishmania antigenic extract (SLA).

CONCLUSIONS

the preliminary data suggest that rMELEISH has the potential to be tested in future studies against a larger serological panel and in field conditions for the diagnosis of canine and human VL.

Ein Update zur Leishmaniose des Hundes: Diagnostik, Therapie und Monitoring

Aufgrund von steigenden Importzahlen von Hunden aus dem Ausland, zunehmendem Reiseverkehr sowie den Veränderungen klimatischer Bedingungen in Europa gewinnen Infektionen mit Leishmania (L.) infantum bei Hunden in Deutschland zunehmend an Bedeutung. Daher sollten auch Hunde aus dem Ausland, die keine klinischen Symptome zeigen, direkt nach Import sowie erneut 6 Monate später auf vektorübertragene Infektionserreger getestet werden. Bei Hunden mit klinischer Symptomatik, die hinweisend auf eine Leishmaniose sind, werden direkte und indirekte Nachweisverfahren sowie eine hämatologische und biochemische Untersuchung unter Einbezug von Serumeiweißelektrophorese sowie Bestimmung des C-reaktiven Proteins empfohlen. Als Leitfaden für die Therapie sowie das Monitoring stehen die LeishVet-Guidelines zur Verfügung. Es stehen leishmanizide und leishmaniostatische Wirkstoffe zur Verfügung, die in first-line, second-line und third-line unterschieden werden. Zur Anpassung der Allopurinol-Dosierung wird der Stufenplan empfohlen. Aufgrund der Veränderung der klimatischen Bedingungen kommt es zu einer Ausbreitung der Habitate von Sandmücken, die als Vektoren der Leishmaniose bekannt sind. Als weitere Infektionsquellen sind Deckakte, transplazentare Infektionen, Bisswunden und Bluttransfusionen beschrieben. Leishmania infantum hat zoonotisches Potential und ist daher auch in Hinblick auf den „One-Health“-Gedanken bedeutend.

Isolation, typing, and drug susceptibility of Leishmania (Leishmania) infantum isolates from dogs of the municipality of Embu das Artes, an endemic region for canine leishmaniasis in Brazil

The parasitic protozoa Leishmania (Leishmania) infantum is the etiological agent of human visceral leishmaniasis and canine leishmaniasis in South America, where Brazil is the most affected country. This zoonotic disease is transmitted by the bite of an infected phlebotomine sand fly and dogs constitute the main domestic reservoir of the parasite. In this study, we screened 2348 dogs of the municipality of Embu das Artes, Brazil, for antibodies against the parasite. Prevalence for canine leishmaniasis seropositivity was 2.81%, as assessed using a Dual-Path Platform rapid test for canine leishmaniasis. Twenty-five seropositive dogs were euthanized for parasite isolation and 14 isolates were successful obtained. Nucleotide sequencing of the internal transcribed spacer confirmed the isolates to be L. (L.) infantum, and very low sequence variability was observed among them. The in vitro susceptibility to miltefosine and paromomycin was assessed and moderate variation in paromomycin susceptibility was found among the isolates in the promastigote and intracellular amastigote stages. On the other hand, in vitro susceptibility to miltefosine of these isolates was homogenous, particularly in the amastigote stage (EC₅₀ values from 0.69 to 2.07 μM). In addition, the miltefosine sensitivity locus was deleted in all the isolates, which does not corroborate the hypothesis that the absence of this locus is correlated with a low in vitro susceptibility. Our findings confirm that the municipality of Embu das Artes is endemic for canine leishmaniasis and that isolates from this region are susceptible to paromomycin and miltefosine, indicating the potential of these drugs to be clinically evaluated in the treatment of human visceral leishmaniasis in Brazil.

Visceral leishmaniasis in a recent transmission region: 27.4% infectivity rate among seronegative dogs

American visceral leishmaniasis (VL) is a parasitic disease whose main domestic reservoir in the urban environment is dog and is considered one of the most important zoonoses in the context of public health. Serological tests are typically used for the diagnostic screening of the disease. This study aimed to analyse the performance of different methodologies used in the diagnosis of VL in dogs sampled from a recent transmission area. The sample consisted of 52 dogs separated into groups based on the absence and presence of clinical signs of VL. The following serological techniques were carried out: the DPP® rapid test (RT), the ALERE® RT and an RT and immunoenzymatic assay with a recently developed protein (rKDDR-plus). In addition, molecular techniques were carried out with conjunctival swabs, and bone marrow aspirate samples and parasitological samples were obtained directly from bone marrow aspirates. It was concluded that 27.4% of seronegative dogs were infected, but the serological tests, used as screening tests, showed unsatisfactory sensitivity results (average: 51.2%) for dogs without clinical signs. It was suggested that polymerase chain reaction with conjunctival swabbing be used as a screening test for dogs without clinical signs, as this is a non-invasive collection technique with high-sensitivity values.

Canine leishmaniasis in an endemic region, Northeastern Brazil: a comparative study with four groups of animals

Canine leishmaniasis (CanL) is a zoonosis caused by protozoa of the genus Leishmania and remains an important public health concern in tropical areas. In Brazil, domestic dogs are considered the most relevant reservoir of the parasite and one of the main targets of the disease control actions. Considering this, we aimed herein to evaluate the CanL infection in different canine groups and distribution of cases in the state of Sergipe, an endemic region in Northeastern Brazil. The evaluated 467 animals were classified into four groups: hunting (n = 50), company (n = 64), guard (n = 140), and wandering (n = 213). Samples (blood, bone marrow, conjunctival swab, and lymph node aspirate) were collected from animals in nine municipalities of Sergipe. First, all animals were submitted to general and ophthalmic clinical examination. Next, they were tested serologically by TR-DPP®, and for the presence of Leishmania, amastigotes in samples of bone marrow, conjunctival swab, and lymph node aspirate were diagnosed by PCR and parasitological techniques. It was observed that 34.69% (162) of the evaluated dogs were seropositive. The highest rates of positivity were found in hunting 54% (27/50; OR = 3.52; p-value = 0.001) and guard dogs 42.14% (59/140; OR = 2.18; p-value = 0.01). Otherwise, the highest percentage of symptomatic dogs was observed in wandering animals (85%; OR = 9.63; p-value < 0.0001). The distribution of case analysis showed that the highest positivity rates occurred in inland municipalities situated in arid regions. Taken together, our data demonstrate that hunting and guard dogs are among the animals most exposed and affected by clinical manifestations of CanL, mainly in the inland municipalities of Sergipe State.

Emergent canine visceral leishmaniasis in Argentina: Comparative diagnostics and relevance to proliferation of human disease

BACKGROUND

Visceral leishmaniasis (VL) is a zoonotic protozoal vector-borne disease that is a major public health challenge. In Argentina, canine (CVL) and human visceral leishmaniasis (HVL) have recently emerged. There is a lack of standardised diagnostic tests for CVL, which hinders control of CVL and HVL.

METHODOLOGY/PRINCIPAL FINDINGS

Sampling was carried out in Puerto Iguazú, Argentina, comprising 190 asymptomatic, oligosymptomatic and polysymptomatic dogs. The following diagnostics were applied: microscopy of lymph node aspirate (LNA); three immunochromatographic rapid diagnostic tests (RDTs), prototype rK28-ICT, rK39-ICT (both Coris BioConcept), commercial rK39 (InBios); ELISA for IgG, IgG1 and IgG2, against rK28, rK39 or crude lysate antigen. DNA detection and analysis, with 30 dogs, was of the ITS1 region using skin samples, and loop-mediated isothermal amplification (LAMP; Eiken Loopamp) of buffy coat, skin scrape or LNA. 15.4% of dogs were positive by LNA microscopy. The rK28 RDT had higher seropositivity rate (61%) than either a prototype rK39 RDT (31.4%) or commercial rK39 RDT (18.8%), without cross-reactivity with six other pathogens. IgG anti-rK39 ELISA antibody titres, but not IgG2, were positively correlated with number of clinical signs. LAMP with LNA had a higher positivity rate than PCR; buffy coat sampling was more sensitive than skin scrape. ITS1 confirmed Leishmania (Leishmania) infantum as the agent of CVL. Leishmania (Viannia) spp. was detected in skin samples from two dogs, compatible with Leishmania (Viannia) braziliensis.

CONCLUSIONS/SIGNIFICANCE

Seroprevalence confirmed rapid increase in CVL in Puerto Iguazú. The rK28 RDT test potentially has great value for improved point-of-care diagnosis. Given cost reduction and accessibility, commercial LAMP may be applicable to buffy coat. RDT biomarkers of CVL clinical status are required to combat spread of CVL and HVL. The presence of Viannia, perhaps as an agent of human mucocutaneous leishmaniasis (MCL), highlights the need for vigilance and surveillance.

Validation of ELISA with recombinant antigens in serological diagnosis of canine Leishmania infantum infection

BACKGROUND

Dogs are the main peridomiciliary reservoir of Leishmania infantum thus the correct diagnosis of infection is essential for the control of the transmission and treatment as well. However, the diagnosis is based on serological assays that are not fully effective.

OBJECTIVE

We aimed to establish an effective serological assay for the diagnosis of L. infantum infected dogs using Leishmania-derived recombinant antigens.

METHODS

Leishmania derived rK39-, rK28-, rKR95-based enzyme-linked immunosorbent assay (ELISA) was standardized using symptomatic and asymptomatic L. infantum-infected dogs. Then 2,530 samples from inquiry in endemic areas for VL were evaluated and the results compared with recommended assays by the Brazilian Ministry of Health (MH algorithm). Further samples from a cohort of 30 dogs were searched.

FINDINGS

For rK39-, rK28- and rKR95-ELISA the sensitivity was around 97% and specificity 100%. The positivity of these three ELISA in the inquiry samples was 27-28%, around 10% higher than the assays currently in use. When cohort samples were searched, we observed likely false-negative results (> 65%) with supposedly negative samples that turned positive six months later with the assays in use (MH algorithm).

MAIN CONCLUSIONS

For the diagnosis of L. infantum-infected dogs, rK39-based ELISA showed better diagnostic performance than other assays in use in Brazil and worldwide.

Leishmania infantum-Derived Glycoinositolphospholipids in the Immunodiagnosis of Subclinically Infected Dogs

Lipophosphoglycan (LPG), when used as an ELISA target, confers high specificity and sensitivity to the detection of Leishmania infantum antibodies in dogs. Glycoconjugates are economically viable because the yield is very high after extraction/purification. In addition, they are very stable, which allows their use in point-of-care testing without special storage conditions. During the glycoconjugate extraction, a glycoinositolphospholipid (GIPL)-enriched fraction is obtained in similar quantities as LPG. Since GIPLs can be extracted from the same parasite pellet as LPGs, this work aimed to evaluate the immune recognition of GIPLs by Leishmania infantum-infected dogs and its use for canine leishmaniasis (CanL) immunodiagnosis. Like LPG, GIPLs were recognized by sera from L. infantum-infected dogs, but with less sensitivity (83.8%). However, 80% (16/20) of subclinically infected dogs were detected as positive in the assay. Different from LPG, the GIPL-based assay achieved a lower specificity (73.7%) and cross-reactions occurred with T. cruzi and L. braziliensis-infected dogs. Although GIPLs exhibited a similar performance to LPG for subclinically L. infantum-infected dogs, the occurrence of cross-reactivities with other protozoa and a lower sensitivity hinders its use for an immunodiagnostic test. In places where those diseases do not co-exist such as in the Mediterranean region, its use for subclinically dogs could be an alternative.

The efficacy of recombinant protein lbk39 for the diagnosis of leishmaniosis in dogs

Visceral leishmaniosis is one of the most important zoonotic diseases on the planet and dogs are the main reservoir of canine visceral leishmaniosis (CVL) in endemic areas. They play an important role in human infection because in dogs the disease appears long time after infection, and they can move uncontrollably, contributing to disperse the parasite. To take the decision to treat the animals or for euthanasia, in an elimination programme, in order to reduce the parasitic load, it is necessary to diagnose correctly, having more effective tools. Our group has developed a new recombinant antigen-based kinesin-related gene of Leishmania braziliensis (Lbk39), which shows 59% amino acid identity to the L. infantum homologue. The Lbk39 gene was synthesized, inserted into the pLEXSY-sat2 vector and transfected into L. tarentolae cells by electroporation. The recombinant protein was secreted in the culture with a C-terminal histidine marker, purified, generating a product at 337.68 μg mL-1. A total of 152 sera from dog's endemic and non-endemic areas were used, being 78 positives and 75 negatives. The antigen Lbk39 showed 100% sensitivity and 96.1% specificity. We compared this antigen with other antigens such as total extract of the parasite, TRDPP, and our data indicate that Lbk39 has potential application in the diagnosis of CVL through antibody detection.

Cytokine profile and parasite load in lymph nodes of dogs naturally infected with Leishmania infantum from distinct epidemiological scenarios in São Paulo State, Brazil

Visceral leishmaniasis (VL) is an important zoonotic vector-borne disease and domestic dogs are considered the main domiciliary and peri-domiciliary reservoir of Leishmania (Leishmania) infantum in South America. Distinct eco-epidemiological scenarios associated to the prevalence of the disease, clusters of parasite genotypes and chemotypes of vectors population are described in Brazil, especially in the state of São Paulo (SP). In this context, the purpose of the present study is to evaluate the clinical signs, histopathological lesions, parasite load and cytokine profile by immunohistochemistry (IHC) in popliteal lymph nodes of canines naturally infected with L. infantum, from different municipalities of the state of SP. Eighty-three dogs with VL, 61 from northwest SP (NWSP) and 22 from southeast SP (SESP), were clinically classified in stage II, with no babesiosis and ehrlichiosis. Subcapsular inflammatory infiltration and histiocytosis were significantly higher in the SESP group (p = 0.0128; 0.0077, respectively). On the other hand, dogs from NWSP revealed 4.6-fold significantly higher parasite burden (p = 0.0004) and higher IHC scores of IL-1β (p = 0.0275) and IL-4 (p = 0.0327) in the popliteal lymph node tissues, which may be associated with the susceptibility and progression of the disease in these dogs. Differences in immune response profile associated with higher parasite load in dogs can also contribute to explain the distinct eco-epidemiological patterns of VL in specific geographic regions.

Correlations between tissue parasite load and common clinical signs in dogs naturally infected by Leishmania infantum

qPCR is being used for the quantification of parasite load in different tissues of dogs infected by Leishmania infantum with or without clinical manifestations. It may be employed in the diagnosis, monitoring of the infection during treatment, and clinical studies for validation of vaccines. Aimed at enhancing the molecular diagnosis and the subsequent monitoring of the infection, this study evaluated the parasite load in several tissues from dogs infected by Leishmania infantum, showing different clinical status. Thus, the qPCR was performed on skin, conjunctival swab, popliteal lymph node, and bone marrow puncture samples taken from 65 dogs naturally infected by L. infantum. Dogs were divided into three groups per clinical score: group 1 (n = 12), included animals with zero points and no clinical manifestations of the disease; group 2 (n = 35), included animals with a score ranging from 1 to 5 points and moderate clinical manifestations; and group 3 (n = 18), included dogs with a score ranging from 6 to 11 points and intensive clinical manifestations. Another analysis was performed classifying the animals into two groups, considering the presence of, or lack of clinical signs of the disease. Analyses of these results showed that the skin was the tissue with a higher parasite load, followed by popliteal lymph node and bone marrow punctures, and conjunctival swab samples having the lowest loads. Furthermore, the skin was also the tissue with the highest parasite load when evaluating the groups individually. Animals in group 3, with intensive clinical manifestations, showed a higher parasite load in different tissues when compared to animals from groups 1 and 2. Finally, animals with clinical manifestations of the disease showed a higher parasite load when compared to dogs with no manifestations. The importance of the dog as a reservoir of L. infantum in nature is reinforced by the demonstration of skin having the highest amount of parasites/μL in this study's analysis, as well as the fact that skin is the main point of access to the parasite vector. Also, a strong and positive correlation between the intensity of clinical manifestations and the increase of parasite load in the skin was observed. In conclusion, skin was the tissue that was demonstrated to be the best option for the molecular diagnosis of L. infantum infection in dogs with varying clinical statuses used in this study.

Canine visceral leishmaniasis in area with recent Leishmania transmission: prevalence, diagnosis, and molecular identification of the infecting species

INTRODUCTION:

Canine visceral leishmaniasis (CVL) is an endemic disease in Brazil, and integrated control actions have been adopted by the Brazilian Ministry of Health to control its spread. However, the transmission profile is unknown in areas with recent CVL cases, including Itaúna, located in the Brazilian state of Minas Gerais, where the present study was carried out.

METHODS:

A total of 2,302 dogs from 12 neighborhoods were serologically tested for canine VL using the current diagnostic protocol adopted by the Brazilian Ministry of Health. Test positivity rate (TPR) and CVL prevalence were determined for each neighborhood. The presence of Leishmania was assessed in 60 seropositive dogs which had been recommended for euthanasia. Twenty-two of them (37%) were asymptomatic, and 38 (63%) were symptomatic for CVL. Parasitological (myeloculture and smear/imprint) and molecular (PCR) methods were employed for Leishmania detection in bone marrow, spleen, mesenteric lymph nodes, and ear skin. The infecting Leishmania species was identified by DNA sequencing.

RESULTS:

CVL prevalence (per 1,000 dogs) varied from 0.0-166.67, depending on the neighborhood, with a mean of 68.96 (SD 51.38). Leishmania DNA was detected in at least one tissue from all seropositive dogs, with comparable TPR among tissues. Leishmania parasites were identified in most (54/60) seropositive dogs, and the infecting parasite was identified as Leishmania infantum in all of these.

CONCLUSIONS:

Prevalence of CVL is a contributor to the spread of visceral leishmaniasis in Itaúna.

Leishmaniasis in cat shelters: A serological, molecular and entomological study

An epidemiological Leishmania spp. and entomological Phlebotomine sandflies survey was performed in cat shelters at leishmaniasis endemic area of Brazil. Blood and conjunctival swab (CS) samples were collected from 94 cats in two animal protection shelters. These samples were subjected to serological tests using the indirect immunofluorescence antibody test (IFAT) and indirect enzyme-linked immunosorbent assay (ELISA) and to molecular test by polymerase chain reaction (PCR). In addition, a Phlebotomine sandflies survey was performed in the same shelters. The analyses revealed a positivity of 31.91% (30/94) through ELISA and 29.79% (28/94) through IFAT. The two serological tests showed a positive association with perfect agreement (k = 0.925). None of the cats were positive by Leishmania spp. DNA. One Lutzomyia (Lutzomyia) longipalpis male was found in one of the cat shelters. The results and the implications of our findings are discussed below.

High Performance of ELISA test using recombinant rLiNTPDase2 from Leishmania infantum: a Phase II diagnosis of Canine Visceral Leishmaniasis

Canine visceral leishmaniasis (CVL) has been the theme of several studies given the importance of dog as natural reservoir of the pathogen Leishmania infantum in endemic regions and its role on dissemination of CVL and human visceral Lesihmaniasis (VL). The current immunodiagnosis of CVL has limitations concerning accuracy, specificity and sensitivity. Therefore, improvements are required. rLiNTPDase2 has been previously highlighted as a new recombinant antigen from L. infantum to the CVL diagnosis by ELISA assay (rLiNTPDase2-ELISA). In this study, we aimed to evaluate rLiNTPDase2-ELISA in a Phase II study with 651 dog sera samples, also comparing it with methodologies previously established and used in epidemiology surveillance in Brazil, an endemic country of CVL and VL. The rLiNTPDase2-ELISA using standard control sera showed high capability to distinguish between positive and negative sera, sensitivity of 92.6% and specificity of 88.5%. The test was reproductive and the kappa statistics judgement "substantial agreement". rLiNTPDase2-ELISA does not show cross-reactivity with ehrlichiosis-reagent sera. However, we verified 15.3% of cross-reactivity with Chagas disease-reagent sera. The performance of rLiNTPDase2-ELISA was evaluated using sera samples from vaccinated dogs (Leish-Tec®). The results showed high agreement with parasitological and PCR results (sensitivity of 100.0% and specificity of 91.7%). Furthermore, we compared the performance of rLiNTPDase2-ELISA in CVL-reagent sera samples from endemic areas, which were previously diagnosed using other tests for CVL: immunofluorescent (IFI-LVC-Bio-Manguinhos), IFI-LVC-Bio-Manguinhos coupled to ELISA (EIE-LVC-Bio-Manguinhos) and the Rapid Dual Path Platform® (TR-DPP®-Bio-Manguinhos) coupled to EIE-LVC-Bio-Manguinhos. rLiNTPDase2-ELISA showed high level of concordance with IFI-LVC-Bio-Manguinhos (88.6%) and with IFI-LVC-Bio-Manguinhos coupled to EIE-LVC-Bio-Manguinhos (82.9%) but not with TR-DPP® -Bio-Manguinhos coupled to EIE-LVC-Bio-Manguinhos (33.3%), which casts doubts on the effectiveness of this latest test. In addition, the rLiNTPDase2 antigen adsorbed in 96-well plate was stable enough to be used at least for three months. Taken together, our data confirmed, by Phase II study using hundreds samples, the good potential of rLiNTPDase2-ELISA to be used in the field as a new diagnostic assay for CVL.

Performance of recombinant proteins in diagnosis and differentiation of canine visceral leishmaniasis infected and vaccinated dogs

Control of canine visceral leishmaniasis (CVL), a major zoonotic disease in Brazil and many other tropical and subtropical countries, remains difficult as an accurate and reliable diagnosis is still missing. In endemic regions, infected dogs are the main parasitic reservoir host of human Visceral leishmaniasis (VL) infection. Vaccination of dogs against Leishmania infection constitutes an important strategy to prevent or to better control CVL, thus, a serological test that can discriminate between antibodies induced by immunization versus infection is highly desirable in order to improve and simplify diagnosis. Here, four recombinant proteins were evaluated for their ability to detect and differentiate between dogs that are infected with Leishmania or have been immunized with the anti-Leishmania vaccine Leish-Tec^®. Receiver operating characteristic (ROC) curve analysis of the four Leishmania-specific IgG ELISA revealed superior performance of rK28, followed by rKLO8, rK39 and rLb6H. The rK28-based ELISA revealed not only the best accuracy against CVL, but also the lowest cross-reactivity with sera from Leish-Tec^® immunized dogs. Our data show that the rK28-based ELISA is highly suitable for CVL screening as it shows high sensitivity with simultaneous low cross-reactivity. Further, the high specificity of the rKLO8 indicates its suitability for the confirmation of CVL diagnosis.

Reactivity of purified and axenic amastigotes as a source of antigens to be used in serodiagnosis of canine visceral leishmaniasis

Although there is a great diversity of techniques and antigens used in the serodiagnosis of canine visceral leishmaniasis (CVL), total sensitivity and specificity have not yet been found. Since the use of amastigote forms in the indirect immunofluorescence assay has shown an improvement in the specificity of the test for the diagnosis of CVL, the performance of amastigotes forms of L. (L.) infantum chagasi as antigen source were evaluated in automatized ELISA test using crude antigen of axenic amastigote and purified amastigote from spleen of hamster chronically infected comparing with ELISA using total antigen produced with promastigote forms of L. (L.) infantum chagasi. One hundred and fifteen sera from dogs with positive parasitological diagnosis by PCR were used. The animals were classified into 2 groups: symptomatic (n = 67) and asymptomatic (n = 48) animals, in accordance with the clinical signs and laboratory tests were. As control, ninety-four sera from dogs with negative parasitological diagnosis were included. No significant difference was found in sensitivity, specificity, predictive values and accuracy between ELISA using whole antigens produced with both axenic and purified amastigotes in comparison with promastigotes forms. Correlation and concordance between the three total antigens tested in ELISA was observed. According to the similar performance among antigens, data pointed out to use antigen from promastigote forms for diagnosing canine leishmaniasis, especially due the easily in the production, lower cost and the abundance of correlative literature.

Canine serological survey and dog culling ant its relationship with human visceral leishmaniasis in an endemic urban area

BACKGROUND

Visceral leishmaniasis is an important but neglected disease that is spreading and is highly lethal when left untreated. This study sought to measure the Leishmania infantum seroprevalence in dogs, the coverage of its control activities (identification of the canine reservoir by serological survey, dog culling and insecticide spraying) and to evaluate its relationship with the occurrence of the disease in humans in the municipalities of Araçatuba and Birigui, state of São Paulo, Brazil.

METHODS

Information from 2006 to 2015 was georeferenced for each municipality and modeling was performed for the two municipalities together. To do this, latent Gaussian Bayesian models with the incorporation of a spatio-temporal structure and Poisson distribution were used. The Besag-York-Mollie models were applied for random spatial effects, as also were autoregressive models of order 1 for random temporal effects. The modeling was performed using the INLA (Integrated Nested Laplace Approximations) deterministic approach, considering both the numbers of cases as well as the coverage paired year by year and lagged at one and two years.

RESULTS

Control activity coverage was observed to be generally low. The behavior of the temporal tendency in the human disease presented distinct patterns in the two municipalities, however, in both the tendency was to decline. The canine serological survey presented as a protective factor only in the two-year lag model.

CONCLUSIONS

The canine serological coverage, even at low intensity, carried out jointly with the culling of the positive dogs, suggested a decreasing effect on the occurrence of the disease in humans, whose effects would be seen two years after it was carried out.

Canine leishmaniasis in the semi-arid region of Pernambuco, northeastern Brazil: epidemiology, factors associated with seropositivity and spatial analysis

This study aimed to determine the seroprevalence, factors associated with seropositivity to Leishmania infection in dogs and spatial analysis in six municipalities in the semiarid region of Pernambuco, Brazil. Blood samples were collected from 462 dogs, 77 in each municipality, and used for serological analysis [dual path platform (DPP®) and enzyme-linked immunosorbent assay (ELISA)]. Clinical signs of dogs were evaluated and associated factors for Leishmania infection were analyzed using robust Poisson regression model. A seroprevalence of 42.8% (198/462, IC: 95% = 38.6%-47.6%) was detected in dogs that tested positive in both tests, ranging from 29.8% to 55.8%, with higher prevalence in the municipality of Cabrobó (55.8%; P = 0.006). About 67% (132/198) of the seropositive dogs showed one or more clinical signs suggestive of canine leishmaniasis (CanL), such as lymphadenomegaly, skin lesions and conjunctivitis, which were associated with seropositivity. High seroprevalence levels were identified in urban and rural areas in all the municipalities, and the buffer for sand flies around cases covered almost these entire areas. Spatial analysis revealed a significant cluster, showing a relative risk of 1.88 in the urban area of Cabrobó. The higher density of seropositive dogs in urban areas indicates the need effective control measures against CanL to prevent the emergence of canine and human diseases.

High seroprevalence and associated factors for visceral leishmaniasis in dogs in a transmission area of Paraíba state, Northeastern Brazil

Dogs have been implicated as main reservoirs for visceral leishmaniasis (VL) in urban areas. Therefore, studies on this species provide important data for public health. Thus, the objective of the present study was to ascertain the seroprevalence of canine VL (CVL) and the associated factors in the Brejo Paraibano microregion, northeastern Brazil. A total of 409 dogs were sampled from the eight municipalities of the microregion: Alagoa Grande, Alagoa Nova, Areia, Bananeiras, Borborema, Matinhas, Pilões and Serraria. The diagnosis of CVL was made using an enzyme-linked immunosorbent assay (ELISA S7®), through which the prevalence observed was 29.3%. By robust Poisson regression analysis two factors were associated with seroprevalence: illiterate/incomplete elementary owner's education level (prevalence ratio = 1.57; 95% CI = 1.05-2.34; p-value = 0.027) and tick infestation (prevalence ratio = 1.82; 95% CI = 1.27-2.61; p-value = 0.001). It is concluded that the seroprevalence of CVL in the Brejo Paraibano microregion is high. The factors associated with seroprevalence indicated the importance to develop socioeducational actions on the population, and the finding that tick infestation was associated with seroprevalence shows that there is a need for investigation regarding the role of ticks in the epidemiology of CVL.

Description d’un nouveau foyer épidémique de leishmaniose cutanée à Leishmania major à l’Ouest du Burkina Faso

Introduction

au Burkina Faso, le seul foyer de leishmaniose cutanée (LC) avec confirmation biologique dans la littérature à notre connaissance est celui de Ouagadougou au centre. Nous rapportons les résultats épidémiologiques, cliniques et biologiques de l’investigation d’un nouveau foyer épidémique à Larama, à l’ouest du Burkina.

Méthodes

la méthode du camp a été utilisée pour recevoir les cas. Les données sociodémographiques et cliniques ont été recueillies à l’aide d’un questionnaire. La confirmation a été faite par la microscopie puis par réaction en chaîne par polymérase (PCR).

Résultats

au total, 108 cas suspects ont été recensés à Larama, soit un taux d’attaque de 5,8%. Le sex ratio était de 1,08. Les patients concernés étaient le plus souvent des cultivateurs (35,2%) et des commerçants (33,3%). La population active (15 à 49 ans) représentait 51,9%. Le nombre de lésion variait entre 1 et 5 dans 91,7% des cas. Les lésions qui se présentaient sous formes ulcéro-crouteuses surélevées et infiltrées, étaient localisées sur les membres (87%) avec une durée d’évolution entre un et cinq mois dans 96,3% des cas. Sur les deux cas prélevés, la microscopie a montré des leishmanies et la PCR a confirmé l’espèce Leishmania major.

Conclusion

nos résultats confirment l’existence d’une épidémie de leishmaniose cutanée à L. major dans l’ouest du pays. Des enquêtes complémentaires sont nécessaires pour préciser la charge de morbidité des leishmanioses au Burkina Faso.

[Control of canine visceral leishmaniasis by euthanasia: estimated effect based on a survey and mathematical modeling]

Visceral leishmaniasis is an emerging and neglected disease that is currently expanding to urban areas. The incidence of human disease is related to canine infection. Araçatuba and Birigui are municipalities (counties) in the state of São Paulo, Brazil, with 8-10% seroprevalence of canine infection and that employ control strategies targeting the canine reservoir, based on serological survey and culling of seropositive dogs. Using data from these control programs to parameterize mathematical models, this study assessed the efficacy of these activities. We estimated that current control is capable of reducing the incidence of canine visceral leishmaniasis (CVL) by approximately 20%. Assuming continuous control and three times the current serological survey activities in Araçatuba and Birigui, culling dogs with a positive CVL diagnosis would be effective for the control of canine infection. Although theoretically possible, in practice the control of CVL with the currently recommended strategies is insufficient, since it would require overcoming the difficulties in these activities, such as lack of material, human, and financial resources, besides associated ethical and legal issues.

Improving the serodiagnosis of canine Leishmania infantum infection in geographical areas of Brazil with different disease prevalence

Serodiagnosis of Leishmania infantum infection in dogs relies on the detection of antibodies against leishmanial crude extracts or parasitic defined antigens. The expansion of canine leishmaniasis from geographical areas of Brazil in which the infection is endemic to regions in which the disease is emerging is occurring. This fact makes necessary the analysis of the serodiagnostic capabilities of different leishmanial preparations in distinct geographical locations. In this article sera from dogs infected with Leishmania and showing the clinical form of the disease, were collected in three distinct Brazilian States and were tested against soluble leishmanial antigens or seven parasite individual antigens produced as recombinant proteins. We show that the recognition of soluble leishmanial antigens by sera from these animals was influenced by the geographical location of the infected dogs. Efficacy of the diagnosis based on this crude parasite preparation was higher in newly endemic regions when compared with areas of high disease endemicity. We also show that the use of three of the recombinant proteins, namely parasite surface kinetoplastid membrane protein of 11 kDa (KMP-11), and two members of the P protein family (P2a and P0), can improve the degree of sensitivity without adversely affecting the specificity of the diagnostic assays for canine leishmaniasis, independently of the geographical area of residence. In addition, sera from dogs clinically healthy but infected were also assayed with some of the antigen preparations. We demonstrate that the use of these proteins can help to the serodiagnosis of Leishmania infected animals with subclinical infections. Finally, we propose a diagnostic protocol using a combination of KMP-11, P2a y P0, together with total leishmanial extracts.

Chemiluminescent ELISA with multi-epitope proteins to improve the diagnosis of canine visceral leishmaniasis

Diagnosing canine visceral leishmaniasis (CVL) is difficult because clinical signs of the disease are non-specific and a many infected animals in endemic areas, as in Brazil, are asymptomatic. Serological tests are the most common diagnostic methods employed, but most have limitations. For this reason, the implementation of a rapid, sensitive, and specific diagnostic test for CVL has become increasingly important. In this study, we adapted a chemiluminescent enzyme-linked immunosorbent assay (CL ELISA), using two multi-epitope recombinant proteins (PQ10 and PQ20) and a crude Leishmania antigen produced using promastigotes of L. infantum, as antigens to detect CVL infection in animals from Belo Horizonte. To investigate cross-reactions, samples from dogs with other infections (babesiosis, ehrlichiosis and Trypanosoma cruzi) were tested. Assay performance validations were conducted to analyse parameters such as variability, reproducibility, and stability. CL ELISA sensitivity/specificity with PQ10 antigen was 93.1%/80.0%; with the PQ20 protein 93.1%/96.6%; and with the crude antigen 75%/73.3%. Inter-assay variability and inter-operator coefficient of variation were <7% and <15%, with PQ10 and PQ20, respectively. The accuracy of the CL ELISA was classified as excellent for PQ10 (AUC = 0.95) and PQ20 (AUC = 0.98) and moderate for the crude antigen (AUC = 0.77). The kappa score for qualitative agreement between two plate lots was excellent for PQ10 (0.89) and good for PQ20 (0.65). PQ20 remained more stable than PQ10. The CL ELISA with recombinant proteins is a promising tool to diagnose CVL.

Performance of different serological tests in the diagnosis of natural infection by Leishmania infantum in dogs

Visceral leishmaniasis (VL) is a zoonosis caused by the parasite Leishmania infantum and the dog is its main reservoir in rural and urban areas. The diagnosis of infection is mainly based on the presence of anti-Leishmania IgG antibodies in the serum of infected dogs. In this study, the sensitivity and specificity of qualitative rapid tests (RTs) dual path platform (DPP) Bio-Manguinhos, rapid enzyme-linked immunosorbent assay (ELISA) IDEXX, Kalazar Detect and ALERE, as well as quantitative ELISA Bio-Manguinhos and in-house indirect immunofluorescence assay (IFA) tests were analyzed in sera from infected and uninfected dogs. Serial dilutions of the in-house IFA were compared with RTs and ELISA Bio-Manguinhos. The results showed that none of the tests reached 100% sensitivity and specificity. There was no statistical difference between the analyzed RTs. The most sensitive test was the DPP Bio-Manguinhos (97.9%), while the rapid ELISA IDEXX showed higher specificity (100%). In the treatment setting of infected and/or diseased animals, quantitative tests for monitoring the evolution of antibody titers are required, which indicates the maintenance of in-house IFA in animal handling. Furthermore, we demonstrate that the RTs present higher sensitivity in serum samples with superior antibody titers obtained in the in-house IFA. However, the RTs exhibited false negatives in samples with low titers of antibodies. Among the RTs, only the DPP Bio-Manguinhos presented better performance in this situation. Therefore, the use of RTs for the diagnosis of VL in dogs with low titers of antibodies, such as asymptomatic, should be carefully evaluated.

Immunodiagnosis of human and canine visceral leishmaniasis using recombinant Leishmania infantum Prohibitin protein and a synthetic peptide containing its conformational B-cell epitope

In the present study, Leishmania infantum's Prohibitin was cloned and, alongside a synthetic peptide, evaluated for the serodiagnosis of visceral and tegumentary leishmaniasis (CVL and TL, respectively) in dogs and humans. For TL diagnosis, this study analyzed serum samples from cutaneous (n = 20) or mucosal (n = 39) leishmaniasis patients, and from Chagas disease (CD) patients (n = 8) and non-infected patients (n = 45). For CVL diagnosis, serum samples from asymptomatic (n = 14), symptomatic (n = 71), non-infected (n = 116), and Leish-Tec®-vaccinated (n = 79) dogs were examined, as well as T. cruzi (n = 11) and Ehrlichia canis (n = 10) infected animals. An indirect ELISA method using rProhibitin showed diagnostic sensitivity and specificity values of 91.76% and 89.91%, respectively. L. infantum SLA showed 86.11% and 48.24% of specificity and sensitivity, respectively, for CVL serodiagnosis, and 98.31% and 84.91% sensitivity and specificity, respectively for TL diagnosis. L. braziliensis SLA showed 75.47% and 83.05% of specificity and sensitivity, respectively, for TL diagnosis. The synthetic peptide showed a better result in TL than in CVL diagnosis. In conclusion, preliminary results suggest that the detection of antibodies against the rProhibitin protein and the synthetic peptide improves the serodiagnosis of TL and CVL.

Multiplex flow cytometry serology to diagnosis of canine visceral leishmaniasis

An accurate diagnosis of visceral leishmaniasis is an essential tool for control of the disease. While serologic methods are very useful, these conventional methodologies still present limitations in terms of sensitivity and specificity. The use of flow cytometry is a worldwide trend in the development of high-performance diagnostic methods. Herein, we describe a new flow cytometry serology test, characterized by the employment of the Cytometric Bead Array microspheres A4 and E4 coated with the recombinant antigens rLci1A and rLci2B respectively, to improve the serodiagnosis of canine visceral leishmaniasis. The tests were conducted in a wide variety of sera groups (n = 140), where the diagnostics development would be optimized accounting not just the ability to identify infected dogs with different clinical status, but also to exclude cross-reaction and differentiate vaccinated dogs from dogs infected. Serological testing of the antigenic system A4-rLci1A showed a sensitivity of 90.0% and specificity of 75%, while the E4-rLci2B testing demonstrated a sensitivity of 95.0% and specificity of 82.5%. The use of a multiplex assay of A4-rLci1A and E4-rLci2B, resulted in a diagnostic improvement, with a sensitivity of 95.0% and specificity of 91.2%. Our results show that this novel flow cytometry serology test is a viable tool for sensitive and specific serodiagnosis. Notably, the combination of distinct antigenic systems allows us to test for antibodies to multiple recombinant antigens from a single serum sample. This benefit emphasizes the importance of this methodology as an alternative in the serological diagnosis.

eNose analysis of volatile chemicals from dogs naturally infected with Leishmania infantum in Brazil

BACKGROUND

Visceral leishmaniasis (VL) in Brazil is a neglected, vector-borne, tropical parasitic disease that is responsible for several thousand human deaths every year. The transmission route involves sand flies becoming infected after feeding on infected reservoir host, mainly dogs, and then transmitting the Leishmania infantum parasites while feeding on humans. A major component of the VL control effort is the identification and euthanasia of infected dogs to remove them as a source of infection. A rapid, non-invasive, point-of-care device able to differentiate between the odours of infected and uninfected dogs may contribute towards the accurate diagnosis of canine VL.

METHODOLOGY/PRINCIPAL FINDINGS

We analysed the headspace volatile chemicals from the hair of two groups of dogs collected in 2017 and 2018 using a bench-top eNose volatile organic chemical analyser. The dogs were categorised as infected or uninfected by PCR analysis of blood samples taken by venepuncture and the number of parasites per ml of blood was calculated for each dog by qPCR analysis. We demonstrated using a robust clustering analysis that the eNose data could be discriminated into infected and uninfected categories with specificity >94% and sensitivity >97%. The eNose device and data analysis were sufficiently sensitive to be able to identify infected dogs even when the Leishmania population in the circulating blood was very low.

CONCLUSIONS/SIGNIFICANCE

The study illustrates the potential of the eNose to rapidly and accurately identify dogs infected with Le. infantum. Future improvements to eNose analyser sensor sensitivity, sampling methodology and portability suggest that this approach could significantly improve the diagnosis of VL infected dogs in Brazil with additional potential for effective diagnosis of VL in humans as well as for the diagnosis of other parasitic diseases.

Evaluation of DPP® and SNAP® Rapid Tests for diagnosis of Leishmania infantum canine infections

INTRODUCTION

Visceral leishmaniasis is a disease that affects humans, wildlife, and domestic species. Since dogs play a key role in urban Leishmania spp. transmission, the Brazilian government maintains the Monitoring and Control Program of Visceral Leishmaniasis (VLMCP) in endemic regions, which promotes awareness campaigns aiming to enhance the control of the infection. The VLMCP recommends the Dual Path Platform (DPP®) canine visceral leishmaniasis test (Bio-Manguinhos, Brazil) for screening and enzyme-linked immunosorbent assay to confirm the infection. The DPP® test is produced and distributed by the Health Ministry to the Municipal Health Centers responsible for the local VLMCP. The test is not available to all the clinics, forcing some veterinarians to use other rapid tests for screening and diagnosis of this disease in their daily routine.

METHODS

The present study was conducted to compare the performance of the DPP® and SNAP® tests using sera from the dogs with confirmed infections of L. infantum and from the dogs with no previous testing, residing in areas with a low Leishmania infection.

RESULTS

There was 97.0% agreement between the two tests. Sensitivity and specificity of the SNAP® test were 96.3% and 100%, respectively. Agreement between both the antibody tests and the parasitological detection methods was 96.8%. The DPP® test had 95.8% sensitivity and 100% specificity.

CONCLUSIONS

The SNAP® and the DPP® tests were virtually equivalent in terms of detection of canine antibodies against L. infantum, and both the tests demonstrated high and similar levels of sensitivity and specificity.

Molecular detection of Leishmania infantum DNA according to clinical stages of leishmaniasis in dog

The aim of this study was to compare molecular tests used to diagnose Leishmania spp. in dogs with different stages of infection. Blood and conjunctival swab (CS) samples from dogs classified in four clinical stages were subjected to different PCR protocols (13A/13B, MC1/MC2, LITSR/L5.8S and LEISH-1/LEISH-2 primers). To the study, 22.3% (48/215) of dogs were classified as without clinical signs, 67.5% (145/215) stage I (mild disease), 7.0% (15/215) stage II (moderate disease) and 3.2% (7/215) stage III (severe disease). The results showed that in blood samples, 13A/13B detected a significant higher number of positive dogs in stage I (25/145) and in total (42/215) (p≤0.05). However, when CS samples were tested, no difference was observed (p>0.05). On the other hand, in blood samples, MC1/MC2 detected significantly fewer positive dogs classified as without clinical signs (0/48), in stage I (0/145) and in total (1/215) (p≤0.05). Likewise, in CS samples, this primers showed also lower detection (1/215) (p≤0.05). So than, we can conclude that PCR on blood samples with 13A/13B primers has greater capacity to detect positive dogs, mainly at the initial of clinical disease than do other primers and MC1/MC2 are not a good choice to detect Leishmania infantum infection in dogs.

Evaluation of three recombinant proteins for the development of ELISA and immunochromatographic tests for visceral leishmaniasis serodiagnosis

BACKGROUND

Visceral Leishmaniasis (VL) is an infectious disease that is a significant cause of death among infants aged under 1 year and the elderly in Brazil. Serodiagnosis is a mainstay of VL elimination programs; however, it has significant limitations due to low accuracy.

OBJECTIVE

This study aimed to evaluate three recombinant Leishmania infantum proteins (rFc, rC9, and rA2) selected from previous proteomics and genomics analyses to develop enzyme-linked immunosorbent assay (ELISA) and immunochromatographic tests (ICT) for the serodiagnosis of human VL (HVL) and canine VL (CVL).

METHODS

A total of 186 human (70 L. infantum-infected symptomatic, 20 other disease-infected, and 96 healthy) and 185 canine (82 L. infantum-infected symptomatic, 27 L. infantum-infected asymptomatic, and 76 healthy) sera samples were used for antibody detection.

FINDINGS

Of the three proteins, rA2 (91.5% sensitivity and 87% specificity) and rC9 (95.7% sensitivity and 87.5% specificity) displayed the best performance in ELISA-HVL and ELISA-CVL, respectively. ICT-rA2 also displayed the best performance for HVL diagnosis (92.3% sensitivity and 88.0% specificity) and had high concordance with immunofluorescence antibody tests (IFAT), ELISA-rK39, IT-LEISH^®, and ELISA_EXT. ICT-rFc, ICT-rC9, and ICT-rA2 had sensitivities of 88.6%, 86.5%, and 87.0%, respectively, with specificity values of 84.0%, 92.0%, and 100%, respectively for CVL diagnosis.

MAIN CONCLUSIONS

The three antigens selected by us are promising candidates for VL diagnosis regardless of the test format, although the antigen combinations and test parameters may warrant further optimisation.

Improving the reference standard for the diagnosis of canine visceral leishmaniasis: a challenge for current and future tests

BACKGROUND

Studies aimed at validating canine visceral leishmaniasis diagnostic tests present heterogeneous results regarding test accuracy, partly due to divergences in reference standards used and different infection evolution periods in animals.

OBJECTIVE

This study aimed to evaluate the accuracy of the rapid test-dual path platform (TR-DPP) (Biomanguinhos®), EIE-Leishmaniose-Visceral-Canina-Biomanguinhos (EIE-LVC) (Biomanguinhos®), enzyme-linked immunosorbent assay (ELISA) rK39 (in-house), and the direct agglutination test (DAT-Canis) against a reference standard comprising parasitological and molecular techniques.

METHODS

A phase II/III validation study was carried out in sample sera from 123 predominantly asymptomatic dogs living in an area endemic for visceral leishmaniasis.

FINDINGS

Sixty-nine (56.1%) animals were considered infected according to the reference standard. For each test, the sensitivity and specificity, respectively, were as follows: TR-DPP, 21.74% [confidence interval (CI)95% 13.64% to 32.82%] and 92.59% (CI95% 82.45% to 97.08%); EIE-LVC, 11.59% (CI95% 5.9% to 21.25%) and 90.74% (CI95% 80.09% to 95.98%); ELISA rK39, 37.68% (CI95% 27.18% to 49.48%) and 83.33% (CI95% 71.26% to 90.98%); and DAT-Canis, 18.84% (CI95% 11.35% to 29.61%) and 96.30% (CI95% 87.46% to 98.98%).

CONCLUSION

We concluded that improving the sensitivity of serum testing for diagnosing asymptomatic dogs must constitute a priority in the process of developing new diagnostic tests to be used in the visceral leishmaniasis control program in Brazil.

Current status and management of canine leishmaniasis in Latin America

Latin America encompasses diverse geographical, cultural and socio-economic conditions, which are reflected in the challenges for infectious disease control in the region. One of the most significant regional infectious diseases for humans and domestic dogs is leishmaniasis, occurring as visceral leishmaniasis (VL) caused by Leishmania infantum (syn. L. chagasi) transmitted by sand flies (Lutzomyia longipalpis) and with a canine reservoir, and the more common cutaneous leishmaniasis (CL) involving multiple Leishmania spp. (particularly L. braziliensis), sand fly vectors and reservoir hosts. VL is spreading within Latin America for reasons related to mass migration of human and canine populations, with incursion into novel environments (e.g. related to deforestation) coupled with a background of poverty and poor public health infrastructure. The challenges for control of VL also include: (1) the accurate identification of infected dogs (particularly subclinically infected dogs) with the current reliance on serological rather than molecular diagnostic methods, (2) controversy surrounding the ethics and efficacy of culling of seropositive dogs, (3) the limited efficacy of currently available canine vaccines and their potential to interfere with interpretation of serological testing, (4) the expense associated with distribution of insecticidal dog collars, which may prove to be the most valuable control method, and (5) the cost and therefore accessibility of licensed medical treatment for canine leishmaniasis by the general population. Resolution of these isssues will necessitate a 'One Health' approach to co-ordination of resources between human and veterinary healthcare.

Validation of the Dual-path Platform chromatographic immunoassay (DPP® CVL rapid test) for the serodiagnosis of canine visceral leishmaniasis

BACKGROUND Visceral leishmaniasis is a major public health challenge in South America, and dogs are its main urban reservoir. OBJECTIVE Validation of the canine Dual-path Platform immunoassay for canine visceral leishmaniasis (DPP® CVL) for a sample set composed of 1446 dogs from different Brazilian endemic areas. METHODS A well-defined reference standard by means of parasitological culture, immunohistochemistry, and histopathology was used. Animals were classified as asymptomatic, oligosymptomatic, or symptomatic. Sensitivity and specificity were assessed as a single set and in clinical groups. A reproducibility assessment of the tests was conducted using the Kappa (κ) index at three different laboratories (A, B, and C). FINDINGS Overall, 89% sensitivity and 70% specificity were obtained for the entire sample set. Analysis of the clinical groups showed a gradual decrease in the sensitivity and an increase in the specificity with the reduction of clinical signs in the dogs that were assessed, reaching a sensitivity of 75% (42.8-94.5%) among asymptomatic dogs and lower specificity of 56% (46.2-66.3%) among symptomatic dogs. Inter-laboratory agreement was substantial (κAB= 0.778; κAC= 0.645; κCB= 0.711). MAIN CONCLUSIONS The test performance is somewhat dependent on canine symptomatology, but such influence was less evident than in previous studies. Favourable results for sensitivity and specificity can be obtained even in asymptomatic animals; however, caution is needed in these evaluations, and the results suggest that the immunochromatographic test may be further improved for better investigation in asymptomatic dogs. The results obtained confirm the usefulness of DPP® CVL for application in serological surveys.

High accuracy of an ELISA test based in a flagella antigen of Leishmania in serodiagnosis of canine visceral leishmaniasis with potential to improve the control measures in Brazil - A Phase II study

BACKGROUND

Canine Visceral leishmaniasis (CVL) is a serious public health problem, thus for its control, the Ministry of Health in Brazil recommends the rapid diagnosis and euthanasia of seropositive dogs in endemic areas. Therefore, our group had previously selected six recombinant proteins (rLci1, rLci2, rLci4, rLci5, rLci8, and rLci12) due to their high potential for CVL diagnostic testing. The present study aims to produce an immunodiagnostic test using the aforementioned antigens, to improve the performance of the diagnosis of CVL recommended by Brazilian Ministry of Health.

METHODOLOGY/PRINCIPAL FINDINGS

To evaluate the recombinant proteins in the serological assays, positive and negative samples were selected based on parasitological test (culture) and molecular test (qPCR) of splenic aspirate. Initially, we selected 135 dog serum samples, 73 positives (symptomatic and asymptomatic) and 62 negatives to screen recombinant proteins on ELISA platform. Then, for rLci5 ELISA validation, 361 serum samples collected in a cross-sectional study were selected, being 183 positives (symptomatic and asymptomatic) and 178 negatives. In the screening of the recombinant proteins, rLci5 was the only protein to present a performance statistically higher than the performance presented by EIE-LVC test, presenting 96% (IC 95%; 85-99%) vs. 83% (IC 95%; 69-92%) of sensitivity for symptomatic dogs, 71% (IC 95%; 49-97%) vs. 54% (IC 95%; 33-74%) for asymptomatic dogs and 94% (IC 95%; 83-99%) vs, 88% (IC 95%; 76-95% of specificity. Thus, the rLci5 protein was selected to compose a final ELISA test. Validation of rLci5 ELISA showed 87% (IC 81-91%) of sensitivity, 94% (IC 95%; 90-97%) of specificity and 90% accuracy. Testing the EIE-LVC with the same validation panel, we observed a lower performance when compared to ELISA rLci5 (sensitivity of 67% (IC 95%; 59-74%), specificity of 87% (IC 95%; 81-92%), and accuracy of 77%). Finally, the performance of current CVL diagnostic protocol recommended by Brazilian Ministry of Health, using DPP-LVC as screening test and EIE-LVC as confirmatory test, was compared with a modified protocol, replacing EIE-LVC by rLci5 ELISA. The current protocol presented a sensitivity of 59% (IC 95%; 52-66%), specificity of 98% (IC 95%; 95-99%) and accuracy of 80% (IC 95%; 76-84%), while the modified protocol presented a sensitivity of 71% (IC 95%; 63-77%), specificity of 99% (IC 95%; 97-100%) and accuracy of 86% (IC 95%; 83-89%).

CONCLUSION

Thus, we concluded that rLci5 ELISA is a promising test to replace EIE-LVC test and increase the diagnostic performance of CVL in Brazil.

Advances toward Diagnostic Tools for Managing Zoonotic Visceral Leishmaniasis

Visceral leishmaniasis (VL) is a life-threatening outcome of Leishmania infantum or Leishmania donovani infection. Dogs are the primary domestic reservoir of L. infantum parasites, and ownership of infected dogs increases the risk of human VL. Controlling infection within dog populations is regarded as critical to VL management in endemic countries, both preventing progression of canine disease and limiting parasite transmission to humans and dogs. Here we discuss various strategies that are used to diagnose canine visceral leishmaniasis (CVL) and the possibilities of adapting these for use within population screening and control programs. In addition, given the variable transmissibility of L. infantum to the sand fly vector, we outline some possibilities for the preferential identification of 'super-spreader' dogs among the overall infected population.

Variables associated with the prevalence of anti-Leishmania spp. antibodies in dogs on the tri-border of Foz do Iguaçu, Paraná, Brazil

The aim of this study was to investigate the occurrence of anti-Leishmania spp. antibodies in dogs from localities in the city of Foz do Iguaçu, Paraná state, Brazil, on the border with Argentina and Paraguay. Blood samples dogs were collected to perform the following serologic tests: immunochromatographic DPP® rapid test, indirect immunoenzymatic assay (ELISA) and indirect immunofluorescence assay (IFA). In 2012, 285 dogs were analyzed on Argentina border, and in 2013, serum samples from 396 dogs on the border of Paraguay were collected. Using ELISA for screening and IFA for the confirmatory test, the results showed that the antibody prevalence was 1.8% (5/285) on the border of Argentina and 3.0% (12/396) on Paraguay border. When using the DPP® for screening and ELISA as a confirmatory analysis, we observed a seroreagent prevalence in dogs of 2.5% (7/285) on Argentina border and 5.1% (20/396) on Paraguay border. The non-public collection of domestic waste (p= 0.0004) was shown to be associated with leishmaniasis. This study shows the presence of leishmaniasis and suggest the emergence of canine visceral leishmaniasis in state of Paraná due to the confirmed occurrence of seroreactive dogs on Argentina and Paraguay border, which has environmental and geographical characteristics that favor the spread of the parasite.

Canine visceral leishmaniasis diagnosis: a comparative performance of serological and molecular tests in symptomatic and asymptomatic dogs

Although serological assays have been widely used for the diagnosis of canine visceral leishmaniasis (CVL), they present different performances depending on the clinical profile of the dogs. This study evaluated the accuracy of serological tests, immunochromatographic (Dual Path Platform: DPP®) and enzyme-linked immunosorbent (ELISA EIE®), for CVL in relation to the detection of Leishmania DNA through real-time polymerase chain reaction (real-time PCR) in samples from symptomatic and asymptomatic dogs from a non-endemic area in the state of Rio Grande do Sul, Southern Brazil. Serum from 140 dogs (39 symptomatic and 101 asymptomatic) was tested by DPP and ELISA followed by real-time PCR. From a total of 140 samples evaluated, Leishmania DNA was detected by real-time PCR in 41.4% (58/140). Moreover, 67.2% of samples positive in real-time PCR were positive in both DPP and ELISA (39/58), showing moderate agreement between methods. In the symptomatic group, one sample non-reactive in both serological assays was positive in real-time PCR, whereas in the asymptomatic group, 17.8% non-reactive or undetermined samples in serological assays were positive in the molecular method. Leishmania DNA was not detected in 17.9% reactive samples by serological assays from the symptomatic group, and in 3.9% from asymptomatic dogs. Real-time PCR demonstrated greater homogeneity between symptomatic and asymptomatic groups compared with DPP and ELISA. The molecular method can help to establish the correct CVL diagnosis, particularly in asymptomatic dogs, avoiding undesirable euthanasia.

Safety Analysis of Leishmania Vaccine Used in a Randomized Canine Vaccine/Immunotherapy Trial

In Leishmania infantum-endemic countries, controlling infection within dogs, the domestic reservoir, is critical to public health. There is a need for safe vaccines that prevent canine progression with disease and transmission to others. Protective vaccination against Leishmania requires mounting a strong, inflammatory, Type 1 response. Three commercially available canine vaccines on the global veterinary market use saponin or inflammatory antigen components (Letifend) as a strong pro-inflammatory adjuvant. There is very little information detailing safety of saponin as an adjuvant in field trials. Safety analyses for the use of vaccine as an immunotherapeutic in asymptomatically infected animals are completely lacking. Leishmania infantum, the causative agent of canine leishmaniasis, is enzootic within U.S. hunting hounds. We assessed the safety of LeishTec^® after use in dogs from two different clinical states: 1) without clinical signs and tested negative on polymerase chain reaction and serology or 2) without clinical signs and positive for at least one Leishmania diagnostic test. Vaccine safety was assessed after all three vaccinations to quantify the number and severity of adverse events. Vaccinated animals had an adverse event rate of 3.09%, whereas placebo animals had 0.68%. Receiving vaccine was correlated with the occurrence of mild, site-specific, reactions. Occurrence of severe adverse events was not associated with having received vaccine. Infected, asymptomatic animals did not have a higher rate of adverse events. Use of vaccination is, therefore, likely to be safe in infected, asymptomatic animals.

Molecular Method Confirms Canine Leishmania Infection Detected by Serological Methods in Non-Endemic Area of Brazil

In Brazil, visceral leishmaniasis (VL) is expanding and becoming urbanized, especially in non-endemic areas such as the State of Rio Grande do Sul. Considering that infected dogs are the main reservoir for zoonotic VL, this study evaluated the prevalence of canine visceral leishmaniasis (CVL) in the metropolitan area of Porto Alegre, a new area of expansion of VL in Brazil. Serum and plasma from 405 asymptomatic dogs from the municipalities of Canoas (n=107), São Leopoldo (n=216), and Novo Hamburgo (n=82) were tested for CVL using immunochromatographic (DPP^®) and ELISA EIE^® assays (2 assays officially adopted by the Brazilian government for the diagnosis of CVL) and real-time PCR to confirm the results. There was no agreement among serological and real-time PCR results, indicating that the Leishmania infection in asymptomatic animals with low parasite load, confirmed by negative parasitological tests (smears and parasite culture), need to be evaluated by molecular methods. The prevalence of LVC in the metropolitan region of Porto Alegre, confirmed by real-time PCR was 4% (5.6% in Canoas and 4.6% in São Leopoldo). The use of molecular method is essential for accurate diagnosis of CVL, especially in asymptomatic dogs in non-endemic areas.

Risk profile for Leishmania infection in dogs coming from an area of visceral leishmaniasis reemergence

Until the 1980s, visceral leishmaniasis was concentrated in poor rural areas of Brazil. The Vale do Rio Doce, located in the Southeastern Brazilian state of Minas Gerais, was an endemic area with high numbers of human and canine cases. Prophylactic measures adopted since the 1960s reduced the number of cases and the region became a 'controlled endemic' area. In the early 1990s, however, the program was interrupted, and the human disease reemerged in 2008. This cross-sectional study evaluated the prevalence and the risk profile of infection of dogs with Leishmania spp in this reemergence area of visceral leishmaniasis. Among a population of approximately 280,000 people, a total of 3835 dog owners were interviewed about socioeconomic conditions, housing, peridomicile features, and their dogs' characteristics and behavior. Blood samples were collected from 5822 dogs of an estimated canine population of 20,000 and anti-Leishmaniasis antibodies were identified using Dual-Path Platform and ELISA. We observed that 1282 of the 5822 dogs were seropositive for the protozoan indicating a seroprevalence of 22%. The risk factors associated with Leishmania infection in dogs were: non-paved backyard (OR 1.4; 95%CI 1.2-1.7); the presence of dry leaves and decaying fruit in the backyard (OR 1.3; 95%CI 1.1-1.5); medium-sized (OR 1.3; 95% 1.1-1.5) or big-sized dogs (OR 1.8; 95%CI 1.5-2.3); short-haired dogs (OR 1.8; 95%CI 1.5-2.1); dogs that slept in the backyard (OR 2.6; 95%CI 1.8-3.6) or in the balcony (OR 1.6; 95%CI 1.1-2.3); and history of canine visceral leishmaniasis in the household (OR 1.3; 95%CI 1.1-1.5). Our results suggest a strong reemergence of canine visceral leishmaniasis after the discontinuation of the control programs. Also, the observed risk factors reinforce the role of health education and environmental management measures to the effective control of the disease.

More than the eyes can see: The worrying scenario of canine leishmaniasis in the Brazilian side of the triple border

A cross-sectional epidemiological study in the extreme-west of the state of Paraná was carried out to access the prevalence, distribution, and risk variables of canine Visceral Leishmaniases (cVL). This study was conducted in three areas, two cities of far west of Parana state: Foz do Iguaçu (FI) and Santa Terezinha de Itaipu (STI), and along two transects between these two municipalities. To sample the entire urban area, the cities (FI and STI) were divided into a grid of squares of 400 m2 (patch). Among the 526 patches, 123 in FI, 40 in the transects and 33 in STI were selected according to the 'worst scenario' criterion. In the transect areas, in each 0.86 km five dogs from houses were surveyed to leishmaniasis. In each patch, blood of five dogs from houses (and from neighborhood when necessary) in the areas that seemed to be the most appropriate for the proliferation of vector were surveyed. The infection of the dogs by cVL were assessed using two serological tests were used (cELISA and TR-DPP®), and, for those seropositive for both methods, the PCR method were used. Moreover, dogs presenting clinical signs or cutaneous lesions were sampled to PCR. The identification of Leishmania species was confirmed using PCR-RFLP followed by DNA sequencing. Micro, meso and macro scale environmental variables were also surveyed and statistically analyzed. The prevalence rate Leishmania infantum was 23.8% in FI, 4.7% in STI and 9.1% in the transects areas. Among the extrinsic variables analysed, the number of vectors and the presence of infected dogs in neighbouring were positively correlated with the occurrence of infected dogs. Dog size was positively correlated with cVL infection, while the quality of the dog's nutrition affected cVL negatively. As for cutaneous leishmaniasis (CL), the first registry of dogs infected with L. braziliensis in the region shows that there is potential for transmission in peri-urban areas, since environmental conditions allow the proliferation of vectors capable of transmitting this species of parasite. cVL is widely spread in FI, with high prevalence. This supports the hypothesis that the parasite has been present in the region for longer than previously believed, despite the fact that the presence of leishmaniais in the region has only been recognized recently. It is important to control the population of dogs infected with L. infantum (parasite and non-antibodies) to prevent the spread of the disease to other dogs and also to people in the region.

Field trial of efficacy of the Leish-tec® vaccine against canine leishmaniasis caused by Leishmania infantum in an endemic area with high transmission rates

BACKGROUND

Because domestic dogs are reservoir hosts for visceral leishmaniasis (VL) in Brazil, one of the approaches used to reduce human disease incidence is to cull infected dogs. However, the results of controlled intervention trials based on serological screening of dogs and killing of seropositive animals are equivocal. A prophylactic vaccine to protect dogs from being infectious to the sand fly vector could be an effective strategy to provide sustained control. Here, we investigated whether a currently licensed commercial subunit rA2 protein-saponin vaccine (Leish-tec®) had an additional effect to dog culling on reducing the canine infectious populations.

METHODOLOGY/PRINCIPAL FINDINGS

This prospective study was conducted in an L. infantum highly endemic area of southeast Brazil. At the onset of the intervention, all of the eligible dogs received through subcutaneous route a three-dose vaccine course at 21-day intervals and a booster on month 12. For the purpose of comparison, newly recruited healthy dogs were included as the exposed control group. To ascertain vaccine-induced protection, dogs were screened on clinical and serological criteria every 6 months for a 2-year follow-up period. Antibody-based tests and histopathological examination of post-mortem tissue specimens from euthanized animals were used as a marker of infection. The standardized vaccine regime, apart from being safe, was immunogenic as immunized animals responded with a pronounced production of anti-A2-specific IgG antibodies. It should be noted the mean seroconversion time for infection obtained among immunized exposed dogs (~ 18 months), which was twice as high as that for unvaccinated ones (~ 9 months). After two transmission cycles completed, the cumulative incidence of infection did differ significantly (P = 0.016) between the vaccinated (27%) and unvaccinated (42%) dogs. However, the expected efficacy for the vaccine in inducing clinical protection was not evident since 43% of vaccine recipients developed disease over time. Our estimates also indicated that immunoprophylaxis by Leish-tec® vaccine in addition to dog culling might not have an impact on bringing down the incidence of canine infection with L. infantum in areas of high transmission rates.

CONCLUSIONS/SIGNIFICANCE

Leish-tec® as a prophylactic vaccine showed promise but needs to be further optimized to be effective in dogs under field conditions, and thereby positively impacts human incidence.

Reliability of techniques used in the diagnosis of canine visceral leishmaniasis by the national control program in Brazil: A survey in an area of recent transmission

One of the key components of the Brazilian Program for the Control of Visceral Leishmaniasis (PCLV) is the euthanasia of Leishmania-infected canine reservoirs, the detection of which depends on a screening procedure involving a Dual Path Platform^® (DPP) immunoassay and a confirmatory enzyme-linked immunosorbent assay (ELISA). The aims of the present study were to evaluate the reliability of these techniques in a region of recent transmission of canine VL, to follow up the seroconversion 3-4 months after the initial diagnosis of DPP reactive but ELISA indeterminate or non-reactive dogs, and to identify the species of Leishmania in circulation in the area. Each animal was submitted to DPP under field conditions, performed by municipal health workers using peripheral blood (DPP-field), to DPP under laboratory conditions using serum (DPP-lab) and to ELISA using serum. The agreements between the tests were determined using McNemar's χ² test, Cohen's kappa coefficient (k) at the 95% confidence interval and prevalence-adjusted bias-adjusted kappa (PABAK). Of the 1130 dogs examined, 74.2% were non-reactive in all three tests applied. Based on the PCLV positive-infection criterion, seroprevalence was 8.9% (101/1130) with 83.2% (84/101) of infected animals showing reactivity in all three tests while 7.8% (8/101) were reactive in DPP-field and ELISA and 8.9% (9/101) in DPP-lab and ELISA. The proportions of disagreements were substantial in all comparisons. Inter-rater reliability between DPP-field and ELISA (k=0.55; PABAK=0.78) and DPP-lab and ELISA (k=0.59; PABAK=0.81) were considered moderate, while that between DPP-field and DPP-lab (k=0.61; PABAK=0.79) was classified as marginally good. The proportion of seroconversions in DPP reactive animals that were initially ELISA indeterminate was significantly higher than in those that were DPP reactive but initially ELISA non-reactive. Restriction fragment length polymorphism analysis revealed the presence of Leishmania infantum, the etiologic agent of VL, in bone marrow samples from VL-infected animals. Our data showed that the techniques and protocols currently employed in the PCLV screening approach are not entirely reliable. Further consideration should be given to monitoring dogs with undetermined results in ELISA and a better training should be provided for health workers responsible for performing DPP tests applied under field conditions.