Abstract
BackgroundVisceral leishmaniasis (VL) caused by Leishmania infantum is an ongoing health problem in southern Europe, where dogs are considered the main reservoirs of the disease. Current data point to a northward spread of VL and canine leishmaniasis (CanL) in Italy, with new foci in northern regions previously regarded as non-endemic.Methodology/Principal findingsMultilocus microsatellite typing (MLMT) was performed to investigate genetic diversity and population structure of L. infantum on 55 samples from infected humans, dogs and sand flies of the E-R region between 2013 and 2017. E-R samples were compared with 10 L. infantum samples from VL cases in other Italian regions (extra E-R) and with 52 strains within the L. donovani complex. Data displayed significant microsatellite polymorphisms with low allelic heterozygosity. Forty-one unique and eight repeated MLMT profiles were recognized among the L. infantum samples from E-R, and ten unique MLMT profiles were assigned to the extra E-R samples. Bayesian analysis assigned E-R samples to two distinct populations, with further sub-structuring within each of them; all CanL samples belonged to one population, genetically related to Mediterranean MON-1 strains, while all but one VL cases as well as the isolate from the sand fly Phlebotomus perfiliewi fell under the second population. Conversely, VL samples from other Italian regions proved to be genetically similar to strains circulating in dogs.Conclusions/SignificanceA peculiar epidemiological situation was observed in northeastern Italy, with the co-circulation of two distinct populations of L. infantum; one population mainly detected in dogs and the other population detected in humans and in a sand fly. While the classical cycle of CanL in Italy fits well into the data obtained for the first population, the population found in infected humans exhibits a different cycle, probably not involving a canine reservoir. This study can contribute to a better understanding of the population structure of L. infantum circulating in northeastern Italy, thus providing useful epidemiologic information for public health authorities.
Highlights
Visceral leishmaniasis (VL) is a vector-borne systemic disease caused by protozoan parasites of the Leishmania donovani (L. donovani) complex
55 L. infantum strains obtained from humans, dogs and sand flies from the Emiliana-Romagna (E-R) region, northeastern Italy, were assessed using multilocus microsatellite typing, a tool applied for population genetic studies
Results were compared with those obtained from 10 samples of visceral leishmaniasis cases occurring in other Italian regions and with 52 strains of the L. donovani complex from other foci of leishmaniasis
Summary
Visceral leishmaniasis (VL) is a vector-borne systemic disease caused by protozoan parasites of the Leishmania donovani (L. donovani) complex. VL is endemic in the Mediterranean Europe, where the disease is caused by Leishmania infantum (L. infantum) and the infection occurs through the bite of infected female phlebotomine sand fly species of the genus Phlebotomus [1] In this area, dogs are considered the principal domestic reservoirs of VL [2]. A remarkable increase of VL cases has been recently reported in the Emilia-Romagna (E-R) region, which is located in northeastern Italy [6,7] Following this increase, the surveillance tasks that were previously implemented for CanL in public kennels of the E-R region [8] have been extended to humans and vectors and included a molecular surveillance of circulating Leishmania strains. Current data point to a northward spread of VL and canine leishmaniasis (CanL) in Italy, with new foci in northern regions previously regarded as non-endemic
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