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Background: Visceral leishmaniasis is a major public health concern in Brazil and the domestic dog is the main source of infection. In this study, we aimed to evaluate the accuracy and reliability of a rapid chromatographic immunoassay based on a dual-path platform for the diagnosis of canine visceral leishmaniasis (CVL)., Methods: Sampling consisted of 428 domestic dogs selected from two neighborhoods in the municipality of Fortaleza, Ceara state, Brazil. The reference standard was composed of three parasitological tests and was applied samples from 333 dogs. The rapid test was used to analyse whole blood and serum samples., Results: Accuracy of the rapid test in whole blood samples through visual reading (n=305), serum samples through electronic reading (n=333) and serum samples through visual reading (n=333), yielded sensitivities of 87.5% (21/24; 95% CI: 66.5 to 96.7), 88% (22/25; 95% CI: 67.5 to 96.8) and 88% (22/25; 95% CI: 67.5 to 96.8), and specificities of 73.3% (206/281; 95% CI: 67.7 to 78.4), 68.2% (210/308; 95% CI: 62.2 to 74.3) and 69.2% (213/308; 95% CI: 63.7 to 74.3), respectively. Agreement between the visual and electronic readings in 428 serum samples were classified as almost perfect (Kappa Index=0.88; 95% CI: 0.83 to 0.93). The positive predictive value of the test using whole blood samples was 21.9% for the 7.9% prevalence detected by the reference standard in the study sample. A sensitivity analysis of the positive predictive value revealed that it remained below 50% in scenarios with a prevalence of up to 20%., Conclusions: The similarity of the accuracy values of the rapid test using whole blood or serum samples, together with its reliable performance in sera through visual and electronic reading, suggests that it may contribute as a screening test for routine use under field-conditions. However, future studies need to improve the accuracy of the test so that it can be successfully implemented in public health programs., (© The Author 2014. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Canine visceral leishmaniasis (CVL) is the major source of human visceral leishmaniasis (VL) and is transmitted from dogs to sand flies to humans. To control the spread of this disease, early and accurate detection of infected dogs is critical but challenging. Here we demonstrate the potential of the Dual-Path Platform (DPP(®)) CVL rapid test for detecting K26/K39-reactive antibodies in sera from clinically symptomatic (n=60) and asymptomatic (n=60) Leishmania infantum-infected dogs. For the specificity evaluation, assays were performed using known negative diagnostic serum samples (n=59) and cross-reaction control sera (n=11) from animals born in a VL-free area of Brazil. The diagnostic kit displayed high specificity (96%) but low sensitivity (47%) in identifying parasite-positive dogs without signs of CVL. However, the test sensitivity was significantly higher (98%) in diseased cases, indicating that this convenient test may be useful to identify the most infectious dogs. Efforts should be pursued to obtain a more sensitive DPP-multiplexed test parameter (i.e. based on simultaneous yet separate antibody detection of carefully selected multiple antigens of diagnostic utility) for effective serodiagnosis of early-infected dogs, as this will likely allow more efficient canine removal regimens than those used in practice by public health services., (Copyright © 2011 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.)

Toxoplasma gondii and Trypanosoma cruzi are zoonotic protozoan parasites that cause disseminated infections in many vertebrate species. The present study determined the seroprevalence of T. gondii and Tr. cruzi in a population of dogs from Virginia. Serum samples were tested from 90 domestic dogs collected from animal shelters in Virginia. Using an indirect immunofluorescent antibody test, sera were examined at a 1 : 50 dilution and antibodies to T. gondii were found in 19 dogs (21%). Antibodies to Tr. cruzi were determined by qualitative immunochromatographic dipstick assay. One (1%) of the 90 dogs had Tr. cruzi antibodies and it was also seropositive for T. gondii. Our findings indicate that dogs are frequently exposed to T. gondii in Virginia, but that antibodies to Tr. cruzi are rare in the same geographical region.

An immunochromatographic assay (Chagas Stat-Pak) was evaluated for the detection of Trypanosoma cruzi antibodies in 4 species of wildlife reservoirs. Antibodies to T. cruzi were detected in raccoons (Procyon lotor) (naturally and experimentally infected) and degus (Octodon degu) (experimentally-infected) using the Chagas Stat-Pak. In naturally exposed wild raccoons, the Chagas Stat-Pak had a sensitivity and specificity of 66.7-80.0% and 96.3%, respectively. Compared with indirect immunofluorescent antibody assay results, seroconversion as determined by Chagas Stat-Pak was delayed for experimentally infected raccoons, but occurred sooner in experimentally infected degus. The Chagas Stat-Pak did not detect antibodies in naturally or experimentally infected Virginia opossums (Didelphis virginiana) or in experimentally infected short-tailed opossums (Monodelphis domestica). These data suggest that the Chagas Stat-Pak might be useful in field studies of raccoons and degus when samples would not be available for more-conventional serologic assays. Because this assay did not work on either species of marsupial, the applicability of the assay should be examined before it is used in other wild species.

Enzyme-linked immunosorbent assays (ELISAs) based on soluble antigens derived from promastigote or amastigote-like stages of Leishmania infantum and on the recombinant rK39 antigen, each in combination with different conjugates [anti-immunoglobulin G1 [IgG1], anti-IgG2, anti-IgG(gamma), and anti-IgG heavy plus light chains], were compared to an immunofluorescent-antibody test (IFAT) and two commercially available rapid test systems (DiaMed-Vet-IT Leish and ID-PaGIA canine leishmaniasis antibody test) for the detection of specific anti-Leishmania antibodies in symptomatic and asymptomatic dogs with proven L. infantum infections. ELISAs based on soluble promastigote and amastigote antigens had very high sensitivities in symptomatic (n = 30; 100%) and asymptomatic dogs (n = 17; 94.1 to 100%), except when combined with the anti-IgG1 conjugate (41.2 to 82.4%). Specificities were high for all combinations (n = 50; 96 to 100%). The rK39 ELISA detected fewer asymptomatic cases (sensitivities, 52.9 to 64.7%) but was highly specific (96 to 100%). The IFAT was 90% sensitive in symptomatic dogs but was significantly less sensitive in asymptomatic cases (29.4%). However, it had an excellent specificity (100%). Test performances of the rapid tests based on the rK39 antigen were comparable to the ELISAs based on the same antigen. ELISAs based on soluble promastigote or amastigote antigens seem to be most suited for the serological diagnosis of canine Leishmania infections in both symptomatic and asymptomatic dogs. IFAT and the rK39 ELISA lack sensitivity in asymptomatic cases but are highly specific. Rapid tests like the rK39 dipstick test or the ID-PaGIA are helpful for confirming clinically suspected cases because of their high specificities in symptomatic animals.