The changing epidemiology of human leishmaniasis in the non-endemic country of Austria between 2000 to 2021, including a congenital case

Background Leishmaniasis is caused by infection with intracellular protozoans of the genus Leishmania. Transmission occurs predominantly by the bite of phlebotomine sandflies, other routes, including congenital transmission, are rare. The disease manifests as either cutaneous, visceral or mucosal/mucocutaneous leishmaniasis. In recent years, changes in the epidemiological pattern have been reported from Europe.Principal findings A total of 311 new and 29 published leishmaniasis cases occurring between 01/01/2000 and 12/31/2021 in Austria were collected and analyzed. These encompassed 146 cutaneous (CL), 14 visceral (VL), 4 mucosal, and 3 cases with concurrent VL and CL. In addition, asymptomatic infections, comprising 11 unspecified cases with Leishmania DNA detectable only in the blood and 162 cases with anti-Leishmania antibodies were reported. Particularly since 2016, the incidence of leishmaniasis has steadily risen, mainly attributable to increasing numbers of CL and cases with positive serology against Leishmania species, whereas the incidence of VL has slowly decreased. Analysis revealed that a shift in the causative species spectrum had occurred and that a substantial number of CL cases were caused by members of the Leishmania donovani/infantum complex. Simultaneous occurrence of VL and CL was identified in immunocompromised individuals, but also in a not yet reported case of an immunocompetent child after vertical transmission.Conclusions The incidence of leishmaniasis has risen in the recent years. The numbers are anticipated to keep rising due to increasing human mobility, including travel and forced migration, growing reservoir host populations as well as expansion and dispersal of vector species caused by climate and habitat changes, urbanization and globalization. Hence, elevated awareness for the disease, including possible transmission in previously non-endemic regions and non-vector transmission modes, support of sandfly surveillance efforts and implementation and establishment of public health interventions in a One Health approach are pivotal in the global efforts to control and reduce leishmaniasis. Leishmaniasis is a vector-borne infectious disease caused by intracellular parasites and affects 12-15 million people worldwide. The clinical presentation is variable, and the disease mainly manifests as cutaneous, visceral or mucosal forms. We collected 340 cases of leishmaniasis occurring in Austria over a period of 21 years and performed an analysis of trends to understand the epidemiology of the disease in a non-endemic Central European country. In addition, we report a rare case of concurrent visceral and cutaneous leishmaniasis which was vertically transmitted to an immunocompetent child. Our analyses revealed that the incidences of cutaneous leishmaniasis are rising in Austria and that a shift in the causative species spectrum has occurred. Due to increased population migration, travel activities of humans and animal hosts, growth and spread of the vector populations facilitated primarily by climate changes, a rising number of leishmaniasis cases can be anticipated in many endemic, but intriguingly also in non-endemic regions. The potential expansion of endemicity necessitates raising awareness towards the burden of this disease and provides an incentive to the global health community to continue their efforts in disease control.