Detection of Leishmania donovani DNA from Oral Swab in Visceral Leishmaniasis

Visceral leishmaniasis (VL) is the most severe form of leishmaniasis and is fatal if left untreated in over 95% of cases. Leishmaniasis is one of the neglected tropical diseases that tend to thrive in developing regions of the world where inadequate access to healthcare makes it difficult for some people to even receive a diagnosis. This study examined the usefulness of oral swabs as specimens for VL diagnosis, by detecting Leishmania donovani DNA in oral swabs from both VL patients and L. donovani-infected mice. Eighty oral swab (OS) and blood buffy coat (BC) samples were collected from suspected VL cases in Bangladesh. These samples were evaluated using Leishmania kinetoplast minicircle DNA (kDNA) in real-time PCR, and the results showed that 62.5% (50/80) and 67.5% (54/80) of the cases tested positive for the BC specimen and OS, respectively. The OS positivity was statistically comparable to the BC. L. donovani DNA was also detected in an oral swab of all infected BALB/c mice by conventional PCR targeting the large subunit ribosomal RNA gene (LSUrRNA), while it was negative in uninfected mice. This study highlights the potential of practical methods for the molecular diagnosis of VL using oral swabs as a non-invasive, simple, and accurate approach.