Diagnostic performance of a qPCR for Leishmania on stained cytological specimens and on filter paper impressions obtained from cutaneous lesions suggestive of canine leishmaniosis.

Background: Detection of Leishmania in cutaneous lesions is possible by visualization of amastigotes. Detection of Leishmania DNA by PCR presents greater sensitivity, and PCR has been used to diagnose cutaneous leishmaniosis in humans using noninvasive clinical specimens.
Objectives: Study I: to determine if Leishmania DNA could be efficiently extracted and amplified from archived Diff-Quik ^® -stained slides of cytological specimens from canine cutaneous lesions. Study II: to evaluate the diagnostic performance of a Leishmania-quantitative (q)PCR on stained cytological specimens and on filter paper impressions (FPI) obtained from cutaneous lesions suggestive of canine leishmaniosis (CanL).
Animals: Samples from cutaneous lesions of 54 dogs.
Methods and Materials: Study I: Leishmania-qPCR was performed on 19 glass slides (from nine dogs) with cytologically visible amastigotes. Fifteen slides with no visible amastigotes, obtained from 12 dogs seronegative for Leishmania by ELISA, served as controls. Study II: Leishmania-qPCR was performed on glass slides and FPI from cutaneous lesions compatible with clinical leishmaniosis in 33 dogs.
Results: Study I: all slides with visible amastigotes had positive qPCR, whereas all control slides yielded negative results. Study II: of 13 dogs definitively diagnosed with clinical leishmaniosis, eight had visible amastigotes on cytology, whereas Leishmania-qPCR was positive on 11 glass slides and 13 FPI. Leishmaniosis was ruled out by standard methods in 20 dogs, four of which yielded positive qPCR on FPI and/or glass slides.
Conclusions and Clinical Importance: Leishmania-DNA can be detected efficiently by qPCR from cutaneous cytological specimens and FPI to diagnose Leishmania infection in dogs with cutaneous lesions suggestive of CanL.
(© 2019 ESVD and ACVD.)