The northward spread of leishmaniasis in Italy: evidence from retrospective and ongoing studies on the canine reservoir and phlebotomine vectors

Abstract

Summary Visceral leishmaniasis (VL) incidence has been increased in Italy in humans and dogs since the 1990s, with new foci being detected within traditional boundaries of endemic transmission but also in northern regions previously regarded as non‐endemic. To monitor the putative VL spreading, surveillance was implemented in northern continental Italy comprising: analysis of human cases recorded from 1990 through 2005; retrospective literature analysis of canine leishmaniasis (CanL) and phlebotomine sandfly records through 2002; prospective investigations in dogs from 2003 through 2005 and surveys on sandflies in 2003 and 2004. Two‐hundred‐thirty human cases (11% of Italian cases) were recorded. Their stratification by age and HIV status disclosed a sharp decrease of HIV/VL co‐infections paralleled by concomitant increase of paediatric and HIV‐negative adult patients during the study period. Four patients had no travel history. Seven leishmaniasis foci were retrospectively identified since 1990, whereas prospective investigations in dogs disclosed 47 autochthonous clinical cases and 106 autochthonous seropositives among 5442 dogs (2.1%) from 16 foci of six regions. Parasites were typed as Leishmania infantum MON‐1. Four vector species were identified among 1696 Phlebotomus (Larroussius) collected specimens. Comparisons with historical data showed that P. perniciosus and P. neglectus have increased in density and expanded their geographic range in the study area. Northern continental Italy is now focally endemic for VL and a moderate risk for human disease does exist, although the intensity of transmission seems to be lower than in traditional settings of Mediterranean VL.

Spread of Vector-borne Diseases and Neglect of Leishmaniasis, Europe

“…However, autochthonous leishmaniasis appears not to be limited to the Mediterranean region anymore. It has spread northward, as shown by the recent reports of indigenous VL cases in northern Italy and southern Germany (8,9).…”

Predicting the distribution of canine leishmaniasis in western Europe based on environmental variables

“…Already, we have demonstrated that country-level risk maps can distinguish well between areas with high (>20%) and low (<5%) CanL seroprevalences (only 3% misclassified using the France-only model) and that seroprevalences are invariably low in areas of CanL emergence. For example, seroprevalence is usually <5% throughout northern Italy above latitude 45·5 0 N, where CanL has emerged within the last 20 years (Maroli et al 2008). The improvement of spatial models for predicting CanL emergence in Europe depends on carrying out new standardized serological and molecular surveys in central and northern Europe as well as at extreme altitudes (< 100 m, >1000 m a.s.l.)…”

“…Therefore, ideally, serology should be complemented by molecular screening in horizontal surveys (Lachaud et al 2002;Quinnell and Courtenay, 2009). Lastly, the resolution of the sampling is inadequate, because a point location was very often an assembly point in a large village, to which dogs were brought for screening from a radius of 10 km or more (Rioux and Golvan, 1969;Maroli et al 2008;Martín-Sánchez et al 2009;Gálvez et al 2010b). To improve the sampling resolution, we recommend including in the model 'dog factors', such as the age and lifestyle of individual dogs recorded as living most of the time in specific geo-referenced habitations.…”

“…Model variation between European countries might be explained by geographical differences in climate and seasonality associated with the bioclimatic and ecological requirements of the sandfly species serving as regional vectors. These considerations prompted us to construct a separate model and risk map for France, where both vectors (P. perniciosus and P. ariasi) have overlapping altitudinal ranges throughout much of the Mediterranean region (Ready, 2008;Chamaillé et al 2010;Hartemink et al 2011), unlike in Italy where 1 of the 2 main vectors (P. perfiliewi, not P. perniciosus) occurs only in the centre-south of the country (Maroli et al 2008). Our best model for France alone, the France-only model, predicted the seroprevalence of CanL based on 6 variables, namely altitude, LSTNmn, amplitude of the bi-annual cycle of the night-time land surface temperature (LSTNa2), LSTNa3, amplitude of the annual cycle of middle infrared reflectance (MIRa1) and amplitude of the tri-annual cycle of middle infrared reflectance (MIRa3).…”

Geographical Distribution of MDR1 Expression in Leishmania Isolates, from Greece and Cyprus, Measured by the Rhodamine-123 Efflux Potential of the Isolates, Using Flow Cytometry

“…[5][6][7] Natural transmission of the parasite may be zoonotic (L. infantum) using the dog as reservoir host or anthroponotic (L. tropica and L. donovani), and it takes place by the bite of insect vectors and blood-sucking phlebotomine sandflies. Although leishmaniasis is spreading geographically [8][9][10][11] favored by the changing conditions, constituting a serious public health threat, the development of parasite resistance to drugs presents an alarming situation.…”