Development of quantitative PCR and digital PCR for the quantification of Leishmania infantum in dogs.

Leishmaniasis is a zoonotic disease with worldwide distribution. In the Americas, the causative agent of the visceral form is the protozoa Leishmania (Leishmania) infantum. Transmission to the host or vertebrate reservoir occurs through the bite of infected arthropod females like Lutzomyia longipalpis. The epidemiological connection between the infection in dogs and humans generate constant studies about the relationship between the parasite and the canine host, including the development of methods and tests for the detection and quantification ofLeishmania (L.) infantum. Both conventional PCR (cPCR) and quantitative PCR (qPCR) can be used in the diagnosis of the parasite. Dropet Digital PCR (ddPCR) is another useful tool. Knowing the parasite load and its relationship with the clinical signs of naturally infected dogs is useful in research development and for establishing treatments that reduce the transmission of the disease. In this study, thirty-nine clinical samples of spleen from dogs naturaly infected by L. infantum were collected after necropsy. Two molecular tools were used to quantify the parasite load (qPCR and ddPCR) and there was 100% agreement in the results of the them. The tools developed in this work are important for the detection of L. infantum in dogs and humans. Droplet Digital PCR does not require a standard curve and is easy to standardize. In such manner, this new tool can generate more in-depth information in the broad debate about parasitic loads and the pathogenesis of leishmaniasis.

Visceral leishmaniasis: a practical strategy for quantitative molecular diagnosis in naturally infected dogs.

The diagnosis of canine visceral leishmaniasis (CVL) has been a problem for public health services due to the variety of clinical signs similar to other diseases and low sensitivity and specificity of available tests. In this sense, our main objective was to develop a simple, rapid, and accurate quantitative real-time PCR (qPCR) diagnosis for CVL. Thus, low-invasive samples from bone marrow (BM), popliteal lymph nodes (PLN), and conjunctival swabs (CS) were selected from negative and VL-positive dogs, using as gold standard, immunological and parasitological tests performed with different tissues. Oligonucleotides for Leishmania infantum kDNA were designed and the limit of quantification and amplification efficiency of the qPCR were determined using tissue-specific standards produced with DNA from those different tissues, mixed with DNA from a known amount of L. infantum promastigotes. Endogenous control was used to validate a comparative Ct method, and tissue parasite concentrations were estimated by comparison with tissue-specific reference standard samples. The overall analysis of the qPCR data suggests the following ranking for tissue choice: PLN > BM > CS. Finally, we have concluded that this molecular approach simplifies and accelerates the quantitative diagnostic process because it is easy to perform, requiring no DNA dosing or standard curve application, and it shows good diagnostic parameters, especially when using popliteal lymph node samples.

Report of the presence of Leishmania infantum in the milk of a naturally infected female dog in Brazil.

Dogs are the most important reservoir of Leishmania infantum, the causal agent of visceral leishmaniasis in Brazil. Although lymphoid tissue is the most important biological tissue where amastigotes can be found, this paper describes the presence of L. infantum DNA in the milk of a lactating naturally infected female dog. This finding suggests the need for further studies to elucidate whether breastfeeding can be a route of infection.

Sand fly bioecological aspects and risk mapping of leishmaniasis by geographical information systems approach in a mineral exploration area of Brazil.

Epidemiological studies of leishmaniasis in areas of great human influence and environmental change serve as important tools for the implementation of effective control plans. Mining is currently a major economic activity in Brazil with the municipality of Pains, in the state of Minas Gerais, being one of the main lime producing municipalities in the country. This study aimed to map areas of potential transmission risks within the municipality of Pains using an epidemiological approach in association with the ecological study of sand flies. Twelve samplings carried out between May 2015 and April 2016 collected a total of 12,728 sandflies, comprising 2,854 females (22.42%) and 9,874 males (77.58%), of 20 species belonging to ten genera. The most abundant species was Lutzomyia longipalpis (80%). Leishmania DNA was detected in seven pools of female sand flies with an infection rate of 0.37%. Geoprocessing and the use of maps revealed that vector sand flies are distributed throughout the urban area, as are cases of canine and human leishmaniasis. However, the greatest abundances of sand flies were at sampling points at the border of the urban area. Higher densities of sand flies and the presence of Leishmania DNA may be correlated with extensive degradation by limestone mining. Integrated and multidisciplinary research approaches are necessary to better understand how the impacts of environmental change influence these insect vectors of leishmaniasis.

Absence of yellow fever virus circulation in wildlife rodents from Brazil.

Yellow fever (YF), caused by the yellow fever virus (YFV), is an emerging viral zoonosis that affects humans and non-human primates (NHP). In South America, YF is naturally maintained through enzootic/sylvatic cycles involving NHPs and mosquitoes (Haemagogus and Sabethes). In this study, we retrospectively analyzed wildlife rodents to better understand their role in a potential alternative YF sylvatic cycle. The plaque reduction neutralization test was performed to detect anti-YFV antibodies, while qPCR targeting the NS5 region of flaviviruses and standard PCR targeting the CprM region were applied to detect YFV RNA in tissue and blood samples. YFV was not evidenced in any of the tested samples. These findings provide additional information regarding sylvatic YFV and emphasize the importance of YFV surveillance in wild animals as potential reservoirs/hosts given the well-established enzootic cycle in the studied areas, mainly in the Atlantic Forest.

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.

Phase II validation study of the rK39 ELISA prototype for the diagnosis of canine visceral leishmaniasis in Brazil.

Dogs are the main reservoirs in the domestic transmission cycle of visceral leishmaniasis, and the diagnosis is essential for the effectiveness of the control measures recommended by the Brazilian Ministry of Health. We assessed the diagnostic performance of the ELISA-Vetlisa/BIOCLIN prototype with serum samples from 200 dogs, in triplicate, including symptomatic, oligosymptomatic, asymptomatic, and healthy dogs, originated by two distinct panels (A and B) characterized by parasitological tests as the reference standard. In this study, the prototype kit showed a 99% sensitivity (95%CI: 94.5-100.0) and a 100% specificity (95%CI: 96.4-100.0). The sensitivity of the prototype kit did not vary significantly with the clinical status of the dogs. Considering the final result classification (positive or negative), agreement between the results of repeated tests was almost perfect (kappa = 0.99; 95%CI: 0.98-1.00). ELISA-Vetlisa/BIOCLIN is a promising option for the serological diagnosis of canine visceral leishmaniasis in Brazil.

Evaluation of the vectorial capacity of Rhipicephalus sanguineus (Acari: Ixodidae) in the transmission of canine visceral leishmaniasis.

The vectorial capacity of Rhipicephalus sanguineus in the transmission of canine visceral leishmaniasis has been evaluated through a laboratory-controlled experiment. One healthy Leishmania-free dog and two dogs naturally infected with Leishmania were infested with R. sanguineus in various stages of development. Engorged larvae, unfed nymphs, engorged nymphs, unfed adults, engorged female adults and fed male adults were collected from the experimental animals and examined for Leishmania infection by optical microscopy, polymerase chain reaction (PCR) and parasite culture. Leishmania forms were not detected in any of the 433 smears prepared from engorged colonies nor in any of the 118 smears prepared from unfed colonies. However, one flagellate structure was identified in one of the smears. All pools of R. sanguineus that had fed on the infected dogs tested PCR-positive for Leishmania DNA, with the single exception of the pool of engorged larvae. In contrast, all pools of ticks that had fed on the Leishmania-free dog were PCR-negative. Leishmania growth was not observed in any of the tick colonies following incubation on culture medium. Considering that no Leishmania forms were identified in any of the meticulously analysed smears derived from engorged colonies of R. sanguineus, it appears somewhat unlikely that the maintenance and multiplication of Leishmania occurs within the tick.

Diversity of phlebotomine sand flies and molecular detection of trypanosomatids in Brumadinho, Minas Gerais, Brazil.

This study aimed to describe the sand fly fauna and detect trypanosomatids in these insects from Casa Branca, state of Minas Gerais, Brazil, an endemic area of both visceral (VL) and tegumentary leishmaniasis (TL). Sand flies were collected bimonthly from May 2013 to July 2014, using automatic light traps exposed for three consecutive nights in peridomiciliary areas of nine houses with previous reports of VL and TL. ITS1-PCR and DNA sequencing were performed for trypanosomatids identification. A total of 16,771 sand flies were collected belonging to 23 species. The most abundant species was Nyssomyia whitmani (Antunes & Coutinho, 1939) (70.9%), followed by Lutzomyia longipalpis (Lutz & Neiva, 1912) (15.2%) and Migonemyia migonei (França, 1920) (9.1%). Leishmania amazonensis DNA was detected in Ny. whitmani (four pools) and Le. braziliensis DNA was detected in Psychodopygus lloydi (one pool). In seven pools of Ny. whitmani and in one pool of Lu. longipalpis positive for Leishmania DNA, the parasite species was not determined due to the low quality of the sequences. Moreover, DNA of Herpetomonas spp. was detected in Ny. whitmani (two pools) and Cortelezzii complex (one pool). DNA of Crithidia spp. was detected in Ny. whitmani and Ps. lloydi (both one pool). Our results suggest that Ny. whitmani may be involved in the transmission of Le. amazonensis in the study area. The molecular detection of Le. amazonensis suggests the presence of this species in a sylvatic cycle between vertebrate and invertebrate hosts in the region of Casa Branca. Our data also reveal the occurrence of other non-Leishmania trypanosomatids in sand flies in Casa Branca District.

Comparative PCR-based diagnosis for the detection of Leishmania infantum in naturally infected dogs.

The applicability of molecular biology/PCR for canine visceral leishmaniasis diagnosis presents challenges, mainly due to the diversity of targets described. The objectives of this study were to compare the sensitivities and reliability of five targets (kDNA/120, kDNA/145, ITS1, hsp70/234 and hsp70/1300) in four different tissue samples (bone marrow, popliteal lymph node, skin and conjunctival swab). Sixty-five dogs (32 males and 33 females) naturally infected with Leishmania infantum and ten dogs without infection were examined. Dogs were characterized by serological and parasitological methods. The parasitological test was considered the gold standard for analysis. All tests presented high specificity 100% (95% CI 0.72-1), and variable sensitivity. The targets kDNA/145, ITS1, kDNA/120, hsp70/234 and hsp70/1300 detected 100% (65/65), 93.4% (61/65), 92.3% (60/65), 84.61% (55/65) and 72.3% (77/65) of positive animals respectively. The performance of PCR methods was analyzed in two different scenarios. The highest sensitivity value identified in all scenarios studied was kDNA/145. Our results suggest that popliteal lymph node and conjunctival swab samples, besides being less invasive collections, represent a good substratum for PCR-based diagnosis, and the target kDNA/145 is the best choice for detecting L. infantum DNA in naturally infected dogs.

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.

Serological, molecular, and microscopic detection of Leishmania in cats (Felis catus) in Belo Horizonte, Minas Gerais State, Brazil.

The role of cats in the epidemiological cycle of leishmaniasis remains unclear. To better understand the occurrence of leishmaniasis in cats, we studied the frequency of Leishmania in serum samples of 100 cats living in an endemic region for canine and human leishmaniasis by serological, parasitological, and molecular methods. Of the 100 cats, 54 were seropositive for Leishmania antibodies by immunofluorescence antibody test. None of the bone marrow aspirates collected from these cats tested positive for the parasite in culture or upon polymerase chain reaction (PCR) analysis. Biopsy samples of the ears also tested negative for Leishmania upon PCR analysis. These findings may indicate that the region is endemic for canine leishmaniasis and cats are infected by Leishmania; or that cross-reaction with antibodies against other parasites increases the frequency of seropositivity; or that cats respond to Leishmania infection by producing antibodies when few or no parasites are present in bone marrow and tissue samples. Overall, our results suggest that cats can be infected by Leishmania ; however, we failed to demonstrate feline parasitosis. These findings highlight the need to study leishmaniasis in cats, since sandflies feed on cats, these animals may act as a reservoir for the parasite.

IgG avidity index and complete blood count as biomarkers of clinical disease in naturally infected dogs with Leishmania infantum.

Canine visceral leishmaniosis (CVL), a parasitic disease caused by Leishmania infantum, may evolve to a chronic condition and lead to death. Evaluation of infected dogs is important to establish the clinical and laboratory parameters involved in the evolution of the disease. The objectives of the present study were to discriminate a canine population (n = 52) into sub-clinical and clinically affected dogs based on signs and scores, to evaluate the hematological, biochemical, histopathological and parasitological parameters of the two dog groups, and to analyze the results by multivariate regression analysis with the aim of establishing biomarkers of CVL clinical disease. The most common signs observed in the clinically affected dogs (n = 29) were hyperkeratosis, weight loss, onychogryphosis, pale mucosa and lymphadenomegaly. In the multivariate analysis, animals presenting high IgG avidity index and low red blood, lymphocyte and eosinophil counts, and low serum urea concentration had an increased probability of being classified as clinically affected (p < 0.05). All five parameters were considered to be strong biomarkers for monitoring the clinical disease, while IgG avidity percentage was strongly correlated with the number of clinical signs and could function as an indicator of the duration of infection. This is the first report on the application of IgG avidity and of multivariate regression analysis in establishing associations between the clinical signs of CVL and host biomarkers. Since avidity index (AI) percentages were strongly correlated with the number of clinical signs, it could be useful in clinical practice for auxiliary diagnosis of CVL and monitoring disease progression. A limitation of this study is the lack of information on co-infections by Anaplasma platys, Babesia canis vogeli, Ehrlichia canis and Hepatozoon canis. Therefore future studies should evaluate the influence of such co-infections on the associations studied using multivariate methods with larger samples.

Detection of Leishmania spp in silvatic mammals and isolation of Leishmania (Viannia) braziliensis from Rattus rattus in an endemic area for leishmaniasis in Minas Gerais State, Brazil.

Knowledge of potential reservoirs of Leishmania spp. in an anthropic environment is important so that surveillance and control measures can be implemented. The aim of this study was to investigate the infection by Leishmania in small mammals in an area located in Minas Gerais, Brazil, that undergoes changes in its natural environment and presents autochthonous human cases of cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL). For the capture of the animals, Sherman and Tomahawk traps were used and distributed in the peridomicile of houses with reports of autochthonous cases of CL or VL. Six catches were carried out on two consecutive nights with intervals of two months during one year and samples of spleen, liver, tail skin, ear skin and bone marrow of the animals were obtained. Parasitological and molecular methods were used to detect the infection. Identification of the Leishmania species was performed by PCR RFLPhsp70. Twenty five animals of four species were captured: ten Rattus rattus, nine Didelphis albiventris, five Cerradomys subflavus and one Marmosops incanus. In the PCR-hsp70, five animals were positive (20%). The Leishmania species identified in PCR-RFLPhsp70 were: Leishmania braziliensis in D. albiventris (2), C. subflavus (1) and R. rattus (1) and Leishmania infantum in R. rattus (1). The highest positivity rate for L. braziliensis was obtained in the liver samples. The spleen was the only tissue positive for L. infantum. It was isolated in culture medium L. braziliensis from two samples (liver and spleen) of R. rattus. This is the first record of isolation of L. braziliensis from R. rattus in the southeastern region of Brazil. These results are relevant to the knowledge of the epidemiology of leishmaniasis in the region, mainly in the investigation of the presence of hosts and possible reservoirs of the parasite.

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.

Molecular survey of Leishmania spp. in skin samples of capybaras (Hydrochoerus hydrochaeris) from different areas of Brazil / Investigação molecular de Leishmania spp. em amostras de pele de capivaras (Hydrochoerus hydrochaeris) de diferentes regiões do Brasil

Leishmaniases comprise a spectrum of diseases caused by protozoan parasites of the genus Leishmania, with some species of rodents being incriminated as reservoirs. The capybara is the largest extant rodent species in the world and is widely distributed in South America. The occurrence of infection by Leishmania spp. was investigated in capybaras captured in Brazil during 2015­2019 from established populations in five highly anthropic areas of the state of São Paulo and two natural areas of the states of Mato Grosso and Mato Grosso do Sul. A total of 186 individuals were captured and subjected to abdominal skin biopsy. All skin samples were Leishmania kDNA-negative, suggesting that capybaras have no role in the transmission cycles of Leishmania species in the studied areas despite the well-known role of other rodents in the life cycle of Leishmania spp.(AU)

As leishmanioses compreendem um espectro de doenças causadas por protozoários do gênero Leishmania e algumas espécies de roedores são incriminadas como reservatórios de Leishmania spp. As capivaras compreendem a maior espécie de roedores existentes e são amplamente distribuídas na América do Sul. Para investigar a ocorrência de infecção por Leishmania spp. em capivaras, durante os anos de 2015-2019 capivaras foram capturadas em cinco áreas antrópicas do estado de São Paulo e em duas áreas naturais dos estados do Mato Grosso e do Mato Grosso do Sul, todos esses ambientes com populações de capivaras estabelecidas. Um total de 186 indivíduos foram capturados e submetidos à biópsia de pele abdominal. Todas as amostras de pele foram negativas para o alvo kDNA, assim, os dados sugerem que nas áreas estudadas as capivaras não têm papel no ciclo de transmissão de espécies de Leishmania spp., apesar do papel bem conhecido de outros roedores no ciclo de vida de Leishmania spp.(AU)

Leishmania (Viannia) braziliensis infection in wild small mammals in ecotourism area of Brazil.

Leishmaniases are parasitic diseases transmitted to mammalian hosts by sand fly vectors (Diptera: Psychodidae). Despite the increasing occurrence of visceral and cutaneous leishmaniasis cases in urban centers, their transmission still occur primarily in wild environments and may be associated with professional activities and recreation, such as ecotourism. The Reserva Particular do Patrimônio Natural Santuário do Caraça (RPPNSC) is one of the largest ecotourism attractions in the State of Minas Gerais, Brazil, and comprises an area of environmental preservation with 11,233 hectares presenting a transitional vegetation between Cerrado and Atlantic Forest. The present study describes the abundance of small mammals in RPPNSC, the isolation and identification of Leishmania in five wild animals. Small mammals were bimonthly trapped along 6 trails within the RPPNSC with 10 Tomahawk traps each. Two trails were located in peridomiciliary areas near tourist lodging facilities, and four trails were located at sites visited by tourists in forest areas. The most prevalent species were Akodon cursor, Cerradomys subflavus and Oligoryzomys nigripes. Six isolates of Leishmania were obtained from these animals and identified as Leishmania braziliensis through HSP70-PCR RFLP method. Leishmania spp. DNA was detected by kDNA-PCR method and isolated by biphasic culture. Studies point to some of the captured species as potential wild reservoirs of Leishmania, suggesting they may be involved in the transmission cycle in these wild environments.

A prototype of the direct agglutination test kit (DAT-Canis) for the serological diagnosis of canine visceral leishmaniasis.

This report describes the stege I/II development of a new direct agglutination test (DAT) for the diagnosis of canine visceral leishmaniasis (CVL) using freeze-dried antigen produced Coomassie blue-stained Leishmania (Leishmania) infantum promastigotes. In stage I, 16 canine serum samples, collected from eight dogs carrying CVL and eight healthy dogs, were assessed with the DAT using 2-mercaptoethanol (2-ME), N-acetyl-cysteine (NAC), kaolin or NAC plus urea (NAC+U) to improve the assay conditions. Stage II assessed the diagnostic accuracy with 100 serum samples collected from dogs with symptomatic CVL and clinically healthy dogs, comparing the four different sample diluents. The CVL-DAT prototype kit showed equivalent performances when 2-ME, NAC or NAC+U were used: 97.1% sensitivity (CI: 83-99.8%), 97% specificity (CI: 88.5-99.5%) and a 97% diagnostic accuracy (CI: 90.8-99.2). With kaolin, a 94.1% sensitivity (CI: 79-99%), 97% specificity (CI: 88.5-99.5%) and 96% diagnostic accuracy were observed (CI: 89.5-98.7), with no statistically significant differences among the four reagents (p=1.0). The NAC plus urea in sample diluent decreased non-specific agglutination, promoted a better defined sharp-edged blue spot and was thus chosen as a component for the new DAT prototype to diagnose canine VL, designated DAT-Canis.

Phase II validation study of the rK39 ELISA prototype for the diagnosis of canine visceral leishmaniasis in Brazil / Estudo de validação da fase II do teste ELISA rK39 para o diagnóstico da leishmaniose visceral canina no Brasil / Estudio de validación de la fase II del test ELISA rK39 para el diagnóstico de la leishmaniasis visceral canina en Brasil

Abstract: Dogs are the main reservoirs in the domestic transmission cycle of visceral leishmaniasis, and the diagnosis is essential for the effectiveness of the control measures recommended by the Brazilian Ministry of Health. We assessed the diagnostic performance of the ELISA-Vetlisa/BIOCLIN prototype with serum samples from 200 dogs, in triplicate, including symptomatic, oligosymptomatic, asymptomatic, and healthy dogs, originated by two distinct panels (A and B) characterized by parasitological tests as the reference standard. In this study, the prototype kit showed a 99% sensitivity (95%CI: 94.5-100.0) and a 100% specificity (95%CI: 96.4-100.0). The sensitivity of the prototype kit did not vary significantly with the clinical status of the dogs. Considering the final result classification (positive or negative), agreement between the results of repeated tests was almost perfect (kappa = 0.99; 95%CI: 0.98-1.00). ELISA-Vetlisa/BIOCLIN is a promising option for the serological diagnosis of canine visceral leishmaniasis in Brazil.

Resumo: Os cães são os principais reservatórios do ciclo de transmissão domiciliar da leishmaniose visceral, e o diagnóstico é essencial para a efetividade das medidas de controle recomendadas pelo Ministério da Saúde. Os autores avaliam o desempenho diagnóstico do protótipo da ELISA-Vetlisa/BIOCLIN em amostras sorológicas de 200 cães, em triplicata, incluindo cães sintomáticos, oligossintomáticos e saudáveis, com dois painéis distintos (A e B) caracterizados por testes parasitológicos enquanto referência. No estudo, o kit-protótipo mostrou sensibilidade de 99% (IC95%: 94,5-100,0) e especificidade de 100% (IC95%: 96,4-100,0). A sensibilidade do kit-protótipo não variou de maneira significativa de acordo com o estado clínico dos cães. Considerando a classificação final dos resultados (positivo ou negativo), a concordância entre os resultados dos testes em triplicata foi quase perfeita (kappa = 0,99; IC95%: 0,98-1,00). O protótipo ELISA-Vetlisa/BIOCLIN tem o potencial de ser utilizada para o diagnóstico sorológico da leishmaniose visceral canina no Brasil.

Resumen: Los perros son los principales reservorios en el ciclo de transmisión doméstica de la leishmaniasis visceral, por ello el diagnóstico es esencial para la efectividad de las medidas de control recomendadas por el Ministerio de Salud de Brasil. Evaluamos el desempeño diagnóstico de ELISA-Vetlisa/BIOCLIN prototipo con muestras de sérum de 200 perros, en triplicado, incluyendo sintomático, oligosintomático, asintomático y perros sanos, originadas por dos paneles distintos (A y B), caracterizados por test parasitológicos como referencia estándar. En este estudio, el kit prototipo mostró un 99% de sensibilidad (IC95%: 94,5-100,0) y un 100% de especificidad (IC95%: 96,4-100,0). La sensibilidad del kit prototipo no varió significativamente con el estatus clínico de los perros. Considerando la clasificación final del resultado (positiva o negativa), el acuerdo entre los resultados de los tests repetidos fue casi perfecto (kappa = 0,99; IC95%: 0,98-1,00). ELISA-Vetlisa/BIOCLIN tiene potencial para ser usado para el diagnóstico serológico de la leishmaniasis visceral canina en Brasil.

Leishmania, Babesia and Ehrlichia in urban pet dogs: co-infection or cross-reaction in serological methods?

INTRODUCTION: The present study was designed to assess the occurrence of co-infection or cross-reaction in the serological techniques used for detecting the anti-Leishmania spp., -Babesia canis vogeli and -Ehrlichia canis antibodies in urban dogs from an area endemic to these parasites. METHODS: The serum samples from dogs were tested for the Babesia canis vogeli strain Belo Horizonte antigen and Ehrlichia canis strain São Paulo by immunofluorescence antibody test (IFAT) and by anti-Leishmania immunoglobulin G (IgG) antibody detection to assess Leishmania infection. We used the following four commercial kits for canine visceral leishmaniasis: ELISA, IFAT, Dual Path Platform (DPP) (Bio Manguinhos(r)/FIOCRUZ/MS) and a rK39 RDT (Kalazar Detect Canine Rapid Test; Inbios). RESULTS: Of 96 serum samples submitted to serological assays, 4 (4.2%) were positive for Leishmania as determined by ELISA; 12 (12.5%), by IFAT; 14 (14.6%) by rK39 RDT; and 20 (20.8%), by DPP. Antibodies against Ehrlichia and Babesia were detected in 23/96 (23.9%) and 30/96 (31.2%) samples, respectively. No significant association was identified between the results of tests for detecting Babesia or Ehrlichia and those for detecting Leishmania (p-value>0.05). CONCLUSIONS: In the present study, we demonstrated co-infection with Ehrlichia or Babesia and Leishmania in dogs from Minas Gerais (Brazil); we also found that the serological tests that were used did not cross-react.