Genetic Variability in Leishmaniasis-Causing Leishmania infantum in Humans and Dogs from North-East Spain.

Leishmania infantum is the primary cause of visceral and cutaneous leishmaniasis in the European Mediterranean region. Subspecies-level characterization of L. infantum aids epidemiological studies by offering insights into the evolution and geographical distribution of the parasite and reservoir identity. In this study, conducted in north-east Spain, 26 DNA samples of L. infantum were analyzed, comprising 21 from 10 humans and 5 from 5 dogs. Minicircle kinetoplast DNA (kDNA) polymerase chain reaction assays using primers MC1 and MC2, followed by sequencing, were employed to assess intraspecific genetic variability. Single-nucleotide polymorphism (SNP) analysis detected seven genotypes (G1, G2, G12*-G15*, and G17*), with five being reported for the first time (*). The most prevalent was the newly described G13 (54%), while the other currently identified genotypes were predominantly found in single samples. The in silico restriction fragment length polymorphism (RFLP) method revealed five genotypes (B, F, N, P, and W), one of them previously unreported (W). Genotype B was the most prevalent (85%), comprising three SNP genotypes (G1, G2, and G13), whereas the other RFLP genotypes were associated with single SNP genotypes. These kDNA genotyping methods revealed significant intraspecific genetic diversity in L. infantum, demonstrating their suitability for fingerprinting and strain monitoring.