The performance of serological tests for Leishmania infantum infection screening in dogs depends on the prevalence of the disease

Abstract

Dogs are considered the main reservoir of Leishmania infantum. This protozoan causes visceral leishmaniasis (VL), an uncontrolled urban zoonosis in Brazil. Serological tests and polymerase chain reaction (PCR) on peripheral blood were performed to identify infected dogs in scenarios of higher and lower prevalence of the disease (Teresina and Vitória). One-hundred infected and 57 non-infected animals from Teresina and 100 non-infected animals from Vitória were studied. Animal selection was not dependent on previous serology. The sensitivity (Teresina) and specificity (Teresina and Vitória) were as follows: indirect antibody fluorescence (IFAT) cut-off of 1:40 (IFAT 1:40): 96%, 18%, and 76%; IFAT 1:80: 90%, 33%, and 93%; direct agglutination test (DAT): 96%, 33%, and 98%; fast agglutination screening test (FAST): 93%, 68%, and 100%; immunochromatographic assay with a recombinant rK39 antigen (rK39): 88%, 74%, and 98%; enzyme linked immunosorbent assay (ELISA): 91%, 79%, and 98%; rapid dual-path platform test (TR DPP®): 98%, 60%, and 98%; and blood PCR: 29%, 93%, and 97%, respectively. In the high transmission area, none of the tests adequately discriminated L. infantum-infected from non-infected dogs. However, in the high transmission city, the area under the receiver operating characteristic (ROC) curve of FAST, DAT, ICrK39, ELISA and TR DPP® was high.

Serological tests fail to discriminate dogs with visceral leishmaniasis that transmit Leishmania infantum to the vector Lutzomyia longipalpis

“…These tests are antibody-based and do not effectively distinguish infected dogs from healthy dogs with an immunological memory of a previous infection, as we have previously shown 16,18 . Therefore, a large number of seropositive, not infective dogs have been culled in Brazil.…”

“…As previously reported 16 , we performed an enzyme-linked immunosorbent assay (ELISA), immunofluorescence antibody tests in 1:40 and 1:80 dilutions (IFAT40 and IFAT80), rapid dual path platform tests (RT-DPP), immunochromatographic assay with a recombinant rK39 antigen (ICrK39), fast agglutination screening tests (FAST), and direct agglutination tests (DAT), and polymerase chain reaction (PCR).…”

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

“… 37 Another more recent study used the direct parasitological test associated with the parasite culture, and it estimated sensitivity for TR-DPP of 100%; its specificity varied between 22 and 96%. 38 The study by Silva et al 39 used serological tests as a reference standard and the TR-DPP’s sensitivity was 58.33% (CI95% 43 to 72). Carvalho et al 10 demonstrated that by using qPCR in blood serum samples, the protocol for CVL diagnosis prescribed by the Ministry of Health had a sensitivity of 67.24% (CI95% 54.42 to 77.92) and specificity of 86.59% (CI95% 77.55 to 92.34).…”

Plasmonic rK28 ELISA improves the diagnosis of canine Leishmania infection

“…In addition, the three observers clearly verified the appearance of a blue‐coloured solution in only the positive samples and a pink‐coloured solution in the negative samples, without conflicting results. The highest specificity of pELISA is an important parameter because an incorrect identification may result in inadequate treatment or unnecessary euthanasia . The pELISA also presented the best PLR and NLR values (1.6 × 10 10 and .05, respectively).…”