Abstract
Visceral leishmaniasis (VL) is a severe disease caused by Leishmania infantum. Dogs are the parasite's main reservoir, favoring its transmission in the urban environment. The analysis of L. infantum from infected dogs contributes to the identification of more virulent parasites, thereby supporting basic and applied studies such as vaccinal and therapeutic strategies. We proposed the in vitro and in vivo characterization of L. infantum strains from naturally infected dogs from a VL endemic area based on an infectivity and pathogenicity analysis. DH82 canine macrophages were infected in vitro with different strains for infectivity analysis, showing distinct infectivity profiles. The strains that showed greater and lesser infectivity using in vitro analyses (616 and 614, respectively) were used to infect hamsters for pathogenicity analysis. The group infected with strain 616 showed 100% survival while the group infected with strain 614 showed 50% after seven months of follow up. Furthermore, the 614 strain induced more noticeable clinicopathological changes and biochemical abnormalities in liver function, along with high inflammation and parasite load in the liver and spleen. We confirmed high variability of infectivity and pathogenicity in L. infantum strains from infected dogs. The results support the belief that screening for L. infantum infectivity using in vitro experiments is inadequate when it comes to selecting the most pathogenic strain.
Highlights
We examined eight different L. infantum strains from dogs with CVL, characterizing them according to in vitro (L. infantum infectivity in DH82 cell linage) and in vivo approaches
We examined different L. infantum strains isolated from dogs living in a Visceral leishmaniasis (VL) endemic area in Brazil, using in vitro and in vivo approaches to determine the infectivity and pathogenicity profiles
This study demonstrated that L. infantum strains, obtained from naturally infected dogs, display different infectivity and pathogenicity profiles
Summary
Leishmania chagasi) is the etiological agent of visceral leishmaniasis (VL) in Latin America, a severe chronic systemic disease [1,2,3]. More than 90% of VL cases reported in the New World occur in Brazil. VL presented a rural epidemiological profile, but it has expanded into urban areas in the past few decades [4, 5]. Dogs are the main domestic reservoir for the parasite in various geographical locations, playing an important role in its transmission to humans [6, 7]. Euthanasia has been shown to have limited effects in controlling visceral leishmaniasis in Brazil [8]
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