Risk of autochthonous human schistosomiasis transmission in Italy

Schistosoma (S.) haematobium is a widespread tropical helminthic zoonosis. Schistosomiasis was endemic in some foci in Southern Europe until the sixties of the last century. Autochthonous transmission of human schistosomiasis was first reported in the French island of Corsica in 2014, and the schistosome responsible for this emergence was also linked to partial hybridisation between S. haematobium and the bovine schistosome species S. bovis. Transmission has recently been retrospectively confirmed in southern Spain as well.

The distance between southern Corsica and northern Sardinia is 12 km. The freshwater snail Bulinus (B.) truncatus, one of the intermediate mollusc hosts of S. haematobium, is known to be endemic in some regions of southern Europe, including Corsica, Spain, and Portugal, where it transmits the zoonotic S. bovis. B. truncatus appears still to be endemic in Sardinia and possibly also in Sicily. Furthermore, schistosomiasis of ungulates caused by S. bovis, transmitted by the same vector snail, also appears to be endemic in Sardinia. Migrant populations and returnees to Italy have been found to be infested with schistosomes, and tourism to local freshwater bodies is increasing.

There is a considerable potential risk of autochthonous schistosomiasis being introduced to Italy. Therefore, surveillance has to be intensified to prevent the establishment of an autochthonous transmission cycle of human schistosomiasis in Italy. Systematic screening strategies for individuals who have been possibly exposed to endemic areas need to be established. Curative treatment of identified cases is mandatory. Praziquantel, the drug of choice, needs to be readily available throughout Italy.Malacological surveillance of snail populations focusing on potential transmission sites is recommended. A one-health approach is recommended to verify the actual epidemiological situation of autochthonous S. bovis infestation and, thereby, to investigate the risk of establishing a zoonotic reservoir. Clinicians should be aware that, in some circumstances, schistosomiasis may occur in individuals who have never travelled to known endemic areas before.