Investigation of canine visceral leishmaniasis in a non-endemic area in Brazil and the comparison of serological and molecular diagnostic tests

Introduction: Visceral leishmaniasis (VL) is an important zoonosis in Brazil. Previous identification of parasitized dogs can also help prevent the disease in humans, even in non-endemic areas of the country. The Brazilian Ministry' of Health recommends diagnosis in dogs using a DPP (R) (rapid test) as a screening test and an immunoenzymatic assay (ELISA) as a confirmatory test (DPP (R)+ELISA), and culling infected dogs as a legal control measure. However, the accuracy of these serological tests has been questioned. Methods: VL in dogs was investigated in a non-endemic area of the Sao Paulo state for three consecutive years, and the performances of different diagnostic tests were compared. Results: A total of 331 dog samples were collected in 2015, 373 in 2016, and 347 in 2017. The seroprevalence by DPP (R)+ELISA was 3.3, 3.2, and 0.3%, respectively, and by indirect immunofluorescence assay (IFA), it was 3.0, 5.6, and 5.5%, respectively. ELISA confirmed 18.4% of DPP (R) positive samples. The concordance between the IFA and DPP (R) was 83.9%. The concordance between IFA and DPP (R)+ELISA was 92.9%. A molecular diagnostic test (PCR) was performed in 63.2% of the seropositive samples, all of which were negative. Conclusions: In non-endemic areas, diagnostic tests in dogs should be carefully evaluated to avoid false results.

Automated summary

Visceral leishmaniasis (VL) is a significant zoonosis in Brazil, with the identification of parasitized dogs being crucial for disease prevention. However, the accuracy of serological tests such as DPP (R)+ELISA has been questioned. A study in a non-endemic area of Sao Paulo state showed fluctuating seroprevalence rates of VL in dogs over three years.